Search

Background Mammalian sex chromosomes provide dosage compensation, but avian lack a global mechanism of dose compensation. Herein, we employed nanopore sequencing to investigate the genetic basis of gene expression and gene dosage effects in avian Z chromosomes at the posttranscriptional level. Results In this study, the gonad and head skin of female and male duck samples (n = 4) were collected at 16 weeks of age for Oxford nanopore sequencing. Our results revealed a dosage effect and local regulation of duck Z chromosome gene expression. Additionally, AS and APA achieve tissue-specific gene expression, and male-biased lncRNA regulates its Z-linked target genes, with a positive regulatory role for gene dosage effects on the duck Z chromosome. In addition, GO enrichment and KEGG pathway analysis showed that the dosage effects of Z-linked genes were mainly associated with the cellular response to hormone stimulus, melanin biosynthetic, metabolic pathways, and melanogenesis, resulting in sex differences. Conclusions Our data suggested that post transcriptional regulation (AS, APA and lncRNA) has a potential impact on the gene expression effects of avian Z chromosomes. Our study provides a new view of gene regulation underlying the dose effects in avian Z chromosomes at the RNA post transcriptional level.

Background Triploid coho salmon are excellent models for studying gene dosage and the effects of increased cell volume on gene expression. Triploids have an additional haploid genome in each cell and have fewer but larger cells than diploid coho salmon to accommodate the increased genome size. Studying gene expression in triploid coho salmon provides insight into how gene expression may have been affected after the salmonid-specific genome duplication which occurred some 90 MYA. Triploid coho salmon are sterile and consequently can live longer and grow larger than diploid congeners in many semelparous species (spawning only once) because they never reach maturity and post-spawning mortality is averted. Triploid fishes are also of interest to the commercial sector (larger fish are more valuable) and to fisheries management since sterile fish can potentially minimize negative impacts of escaped fish in the wild. Results The vast majority of genes in liver tissue had similar expression levels between diploid and triploid coho salmon, indicating that the same amount of mRNA transcripts were being produced per gene copy (positive gene dosage effects) within a larger volume cell. Several genes related to nutrition and compensatory growth were differentially expressed between diploid and triploid salmon, indicating that some loci are sensitive to cell size and/or DNA content per cell. To examine how robust expression between ploidies is under different conditions, a genetic/metabolic modifier in the form of different doses of a growth hormone transgene was used to assess gene expression under conditions that the genome has not naturally experienced or adapted to. While many (up to 1400) genes were differentially expressed between non-transgenic and transgenic fish, relatively few genes were differentially expressed between diploids and triploids with similar doses of the transgene. These observations indicate that the small effect of ploidy on gene expression is robust to large changes in physiological state. Conclusions These findings are of interest from a gene regulatory perspective, but also valuable for understanding phenotypic effects in triploids, transgenics, and triploid transgenics that could affect their utility in culture conditions and their fitness and potential consequences of release into nature. Electronic supplementary material The online version of this article (10.1186/s12864-019-5655-8) contains supplementary material, which is available to authorized users.

Background Goats (Capra hircus), one of the first domesticated species, are economically important for milk and meat production, and their broad geographical distribution reflects their successful adaptation to diverse environmental conditions. Despite the relevance of this species, the genetic research on the goat traits is limited compared to other domestic species. Thanks to the latest goat reference genomic sequence (ARS1), which is considered to be one of the most continuous assemblies in livestock, we deduced the genomic structure of the T cell receptor beta (TRB) and gamma (TRG) loci in this ruminant species. Results Our analyses revealed that although the organization of the goat TRB locus is broadly similar to that of the other artiodactyl species, with three in-tandem D-J-C clusters located at the 3′ end, a complex and extensive series of duplications have occurred in the V genes at the 5′ end, leading to a marked expansion in the number of the TRBV genes. This phenomenon appears to be a feature of the ruminant lineage since similar gene expansions have also occurred in sheep and cattle. Likewise, the general organization of the goat TRG genes is typical of ruminant species studied so far, with two paralogous TRG loci, TRG1 and TRG2, located in two distinct and distant positions on the same chromosome as result of a split in the ancestral locus. Each TRG locus consists of reiterated V-J-J-C cassettes, with the goat TRG2 containing an additional cassette relative to the corresponding sheep and cattle loci. Conclusions Taken together, these findings demonstrate that strong evolutionary pressures in the ruminant lineage have selected for the development of enlarged sets of TRB and TRG genes that contribute to a diverse T cell receptor repertoire. However, differences observed among the goat, sheep and cattle TRB and TRG genes indicate that distinct evolutionary histories, with independent expansions and/or contractions, have also affected each ruminant species.

Background Necrotrophic effector proteins secreted by fungal pathogens are important virulence factors that mediate the development of disease in wheat. Pyrenophora tritici-repentis (Ptr), the causal agent of wheat tan spot, has a race structure dependent on the combination of effectors. In Ptr, ToxA and ToxB are known proteinaceous effectors responsible for necrosis and chlorosis respectively. While Ptr ToxA is encoded by the single gene ToxA, ToxB has multiple loci in the Ptr genome, which is postulated to be directly related to the level of ToxB production and leaf chlorosis. Although previous analysis has indicated that the majority of the ToxB loci lie on a single chromosome, the exact number and chromosomal locations for all the ToxB loci have not been fully identified. Results In this study, we have sequenced the genome of a race 5 ToxB-producing isolate (DW5), using PacBio long read technology, and found that ToxB duplications are nested in the complex subtelomeric chromosomal regions. A total of ten identical ToxB gene copies were identified and based on flanking sequence identity, nine loci appeared associated with chromosome 11 and a single copy with chromosome 5. Chromosome 11 multiple ToxB gene loci were separated by large sequence regions between 31 and 66 kb within larger segmental duplications in an alternating pattern related to loci strand, and flanked by transposable elements. Conclusion This work provides for the first time the full accompaniment of ToxB loci and surrounding regions, and identifies the organization and distribution of ten ToxB loci to subtelomeric regions. To our knowledge, this is the first report of an interwoven strand-related duplication pattern event. This study further highlights the importance of resolving the highly complex distal chromosomal regions, that remain difficult to assemble, and can harbour important effectors and virulence factors.

Background The circadian clock drives endogenous 24-h rhythms that allow organisms to adapt and prepare for predictable and repeated changes in their environment throughout the day-night (diurnal) cycle. Many components of the circadian clock in Arabidopsis thaliana have been functionally characterized, but comparatively little is known about circadian clocks in grass species including major crops like maize and sorghum. Results Comparative research based on protein homology and diurnal gene expression patterns suggests the function of some predicted clock components in grasses is conserved with their Arabidopsis counterparts, while others have diverged in function. Our analysis of diurnal gene expression in three panicoid grasses sorghum, maize, and foxtail millet revealed conserved and divergent evolution of expression for core circadian clock genes and for the overall transcriptome. We find that several classes of core circadian clock genes in these grasses differ in copy number compared to Arabidopsis, but mostly exhibit conservation of both protein sequence and diurnal expression pattern with the notable exception of maize paralogous genes. We predict conserved cis-regulatory motifs shared between maize, sorghum, and foxtail millet through identification of diurnal co-expression clusters for a subset of 27,196 orthologous syntenic genes. In this analysis, a Cochran–Mantel–Haenszel based method to control for background variation identified significant enrichment for both expected and novel 6–8 nucleotide motifs in the promoter regions of genes with shared diurnal regulation predicted to function in common physiological activities. Conclusions This study illustrates the divergence and conservation of circadian clocks and diurnal regulatory networks across syntenic orthologous genes in panacoid grass species. Further, conserved local regulatory sequences contribute to the architecture of these diurnal regulatory networks that produce conserved patterns of diurnal gene expression.

Background Despite the importance of characterizing genetic variation among coral individuals for understanding phenotypic variation, the correlation between coral genomic diversity and phenotypic expression is still poorly understood. Results In this study, we detected a high frequency of genes showing presence–absence polymorphisms (PAPs) for single-copy genes in Acropora digitifera. Among 10,455 single-copy genes, 516 (5%) exhibited PAPs, including 32 transposable element (TE)-related genes. Five hundred sixteen genes exhibited a homozygous absence in one (102) or more than one (414) individuals (n = 33), indicating that most of the absent alleles were not rare variants. Among genes showing PAPs (PAP genes), roughly half were expressed in adults and/or larvae, and the PAP status was associated with differential expression among individuals. Although 85% of PAP genes were uncharacterized or had ambiguous annotations, 70% of these genes were specifically distributed in cnidarian lineages in eumetazoa, suggesting that these genes have functional roles related to traits related to cnidarians or the family Acroporidae or the genus Acropora. Indeed, four of these genes encoded toxins that are usually components of venom in cnidarian-specific cnidocytes. At least 17% of A. digitifera PAP genes were also PAPs in A. tenuis, the basal lineage in the genus Acropora, indicating that PAPs were shared among species in Acropora. Conclusions Expression differences caused by a high frequency of PAP genes may be a novel genomic feature in the genus Acropora; these findings will contribute to improve our understanding of correlation between genetic and phenotypic variation in corals.

Background Plants synthesize glutamate from ammonium by the combined activity of the enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT) through the glutamate synthase cycle. In plants, there are two forms of glutamate synthases that differ in their electron donors, NADH-GOGAT (EC 1.4.1.14) and Fd-GOGAT (EC 1.4.7.1), which have differential roles either in primary ammonia assimilation or in the reassimilation of ammonium from different catabolic processes. Glutamate synthases are complex iron-sulfur flavoproteins containing functional domains involved in the control and coordination of their catalytic activities in annual plants. In conifers, partial cDNA sequences for GOGATs have been isolated and used for gene expression studies. However, knowledge of the gene structure and of phylogenetic relationships with other plant enzymes is quite scant. Results Technological advances in conifer megagenomes sequencing have made it possible to obtain full-length cDNA sequences encoding Fd- and NADH-GOGAT from maritime pine, as well as BAC clones containing sequences for NADH-GOGAT and Fd-GOGAT genes. In the current study, we studied the genomic organization of pine GOGAT genes, the size of their exons/introns, copy numbers in the pine genome and relationships with other plant genes. Phylogenetic analysis was performed, and the degree of preservation and dissimilarity of key domains for the catalytic activities of these enzymes in different taxa were determined. Conclusions Fd- and NADH-GOGAT are encoded by single-copy genes in the maritime pine genome. The Fd-GOGAT gene is extremely large spanning more than 330 kb and the presence of very long introns highlights the important contribution of LTR retrotransposons to the gene size in conifers. In contrast, the structure of the NADH-GOGAT gene is similar to the orthologous genes in angiosperms. Our phylogenetic analysis indicates that these two genes had different origins during plant evolution. The results provide new insights into the structure and molecular evolution of these essential genes. Electronic supplementary material The online version of this article (doi: 10.1186/s12864-018-4454-y) contains supplementary material, which is available to authorized users.

Background DUF1220 protein domains found primarily in Neuroblastoma BreakPoint Family (NBPF) genes show the greatest human lineage-specific increase in copy number of any coding region in the genome. There are 302 haploid copies of DUF1220 in hg38 (~160 of which are human-specific) and the majority of these can be divided into 6 different subtypes (referred to as clades). Copy number changes of specific DUF1220 clades have been associated in a dose-dependent manner with brain size variation (both evolutionarily and within the human population), cognitive aptitude, autism severity, and schizophrenia severity. However, no published methods can directly measure copies of DUF1220 with high accuracy and no method can distinguish between domains within a clade. Results Here we describe a novel method for measuring copies of DUF1220 domains and the NBPF genes in which they are found from whole genome sequence data. We have characterized the effect that various sequencing and alignment parameters and strategies have on the accuracy and precision of the method and defined the parameters that lead to optimal DUF1220 copy number measurement and resolution. We show that copy number estimates obtained using our read depth approach are highly correlated with those generated by ddPCR for three representative DUF1220 clades. By simulation, we demonstrate that our method provides sufficient resolution to analyze DUF1220 copy number variation at three levels: (1) DUF1220 clade copy number within individual genes and groups of genes (gene-specific clade groups) (2) genome wide DUF1220 clade copies and (3) gene copy number for DUF1220-encoding genes. Conclusions To our knowledge, this is the first method to accurately measure copies of all six DUF1220 clades and the first method to provide gene specific resolution of these clades. This allows one to discriminate among the ~300 haploid human DUF1220 copies to an extent not possible with any other method. The result is a greatly enhanced capability to analyze the role that these sequences play in human variation and disease. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3976-z) contains supplementary material, which is available to authorized users.

Background A pool of small RNA fragments (RFs) derived from diverse cellular RNAs has recently emerged as a rich source of functionally relevant molecules. Although their formation and accumulation has been connected to various stress conditions, the knowledge on RFs produced upon viral infections is very limited. Here, we applied the next generation sequencing (NGS) to characterize RFs generated in the hepatitis C virus (HCV) cell culture model (HCV-permissive Huh-7.5 cell line). Results We found that both infected and non-infected cells contained a wide spectrum of RFs derived from virtually all RNA classes. A significant fraction of identified RFs accumulated to similar levels as miRNAs. Our analysis, focused on RFs originating from constitutively expressed non-coding RNAs, revealed three major patterns of parental RNA cleavage. We found that HCV infection induced significant changes in the accumulation of low copy number RFs, while subtly altered the levels of high copy number ones. Finally, the candidate RFs potentially relevant for host-virus interactions were identified. Conclusions Our results indicate that RFs should be considered an important component of the Huh-7.5 transcriptome and suggest that the main factors influencing the RF biogenesis are the RNA structure and RNA protection by interacting proteins. The data presented here significantly complement the existing transcriptomic, miRnomic, proteomic and metabolomic characteristics of the HCV cell culture model. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3891-3) contains supplementary material, which is available to authorized users.

Background Grass carp is an important farmed fish in China that is affected by serious disease, especially hemorrhagic disease caused by grass carp reovirus (GCRV). The mechanism underlying the hemorrhagic symptoms in infected fish remains to be elucidated. Although GCRV can be divided into three distinct subtypes, differences in the pathogenesis and host immune responses to the different subtypes are still unclear. The aim of this study was to provide a comprehensive insight into the grass carp response to different GCRV subtypes and to elucidate the mechanism underlying the hemorrhagic symptoms. Results Following infection of grass carp, GCRV-I was associated with a long latent period and low mortality (42.5%), while GCRV-II was associated with a short latent period and high mortality (81.4%). The relative copy number of GCRV-I remained consistent or decreased slightly throughout the first 7 days post-infection, whereas a marked increase in GCRV-II high copy number was detected at 5 days post-infection. Transcriptome sequencing revealed 211 differentially expressed genes (DEGs) in Group I (66 up-regulated, 145 down-regulated) and 670 (386 up-regulated, 284 down-regulated) in Group II. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed significant enrichment in the terms or pathways involved in immune responses and correlating with blood or platelets. Most of the DEGs in Group I were also present in Group II, although the expression profiles differed, with most DEGs showing mild changes in Group I, while marked changes were observed in Group II, especially the interferon-related genes. Many of the genes involved in the complement pathway and coagulation cascades were significantly up-regulated at 7 days post-infection in Group II, suggesting activation of these pathways. Conclusion GCRV-I is associated with low virulence and a long latent period prior to the induction of a mild host immune response, whereas GCRV-II is associated with high virulence, a short latent period and stimulates a strong and extensive host immune response. The complement and coagulation pathways are significantly activated at 7 days post-infection, leading to the endothelial cell and blood cell damage that result in hemorrhagic symptoms. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3824-1) contains supplementary material, which is available to authorized users.

[Background]: The comparison of expression QTL (eQTL) maps obtained in different tissues is an essential step to understand how gene expression is genetically regulated in a context-dependent manner. In the current work, we have compared the transcriptomic and eQTL profiles of two porcine tissues (skeletal muscle and liver) which typically show highly divergent expression profiles, in 103 Duroc pigs genotyped with the Porcine SNP60 BeadChip (Illumina) and with available microarray-based measurements of hepatic and muscle mRNA levels. Since structural variation could have effects on gene expression, we have also investigated the co-localization of cis-eQTLs with copy number variant regions (CNVR) segregating in this Duroc population., [Results]: The analysis of differential expresssion revealed the existence of 1204 and 1490 probes that were overexpressed and underexpressed in the gluteus medius muscle when compared to liver, respectively (|fold-change| > 1.5, q-value, [Conclusion]: Despite the fact that there are considerable differences in the gene expression patterns of the porcine liver and skeletal muscle, we have identified a substantial proportion of common cis-eQTLs regulating gene expression in both tissues. Several of these cis-eQTLs influence the mRNA levels of genes with important roles in meat (CTSF) and carcass quality (TAPT1), lipid metabolism (TMEM97) and obesity (MARC2), thus evidencing the practical importance of dissecting the genetic mechanisms involved in their expression., Part of the research presented in this publication was funded by grants AGL2013–48742-C2–1-R and AGL2013–48742-C2–2-R awarded by the Spanish Ministry of Economy and Competitivity. We also acknowledge the support of the Spanish Ministry of Economy and Competitivity for the Center of Excellence Severo Ochoa 2016–2019 (SEV-2015-0533) grant awarded to the Centre for Research in Agricultural Genomics. Ángela Cánovas was funded under the Juan de la Cierva program awarded by the Spanish Ministry of Science. Taina F Cardoso was funded with a fellowship from the CAPES Foundation-Coordination of Improvement of Higher Education, Ministry of Education (MEC) of the Federal Government of Brazil. Rayner González-Prendes was funded by a FPU Ph.D. grant from the Spanish Ministry of Education (FPU12/00860). Emilio Mármol-Sánchez was funded by a FPU Ph.D. grant from the Spanish Ministry of Education (FPU15/01733).

Background Hexaploid bread wheat (Triticum aestivum L) arose by two polyploidisation events from three diploid species with homoeologous genomes. Nullisomic-tetrasomic (nulli-tetra or NT) lines are aneuploid wheat plants lacking two and adding two of six homoeologous chromosomes. These plants can grow normally, but with significantly morphological variations because the adding two chromosomes or the remaining four chromosomes compensate for those absent. Despite these interesting phenomena, detailed molecular mechanisms underlying dosage deletion and compensation in these useful genetic materials have not been determined. Results By sequencing the transcriptomes of leaves in two-week-old seedlings, we showed that the profiles of differentially expressed genes between NT stocks for homoeologous group 7 and the parent hexaploid Chinese Spring (CS) occurred throughout the whole genome with a subgenome and chromosome preference. The deletion effect of nulli-chromosomes was compensated partly by the tetra-chromosomes via the dose level of expressed genes, according to the types of homoeologous genes. The functions of differentially regulated genes primarily focused on carbon metabolic process, photosynthesis process, hormone metabolism, and responding to stimulus, and etc., which might be related to the defective phenotypes that included reductions in plant height, flag leaf length, spikelet number, and kernels per spike. Conclusions The perturbation of the expression levels of transcriptional genes among the NT stocks for homoeologous group 7 demonstrated the gene dosage effect of the subgenome at the genome-wide level. The gene dosage deletion and compensation can be used as a model to elucidate the functions of the subgenomes in modern polyploid plants. Electronic supplementary material The online version of this article (10.1186/s12864-018-5421-3) contains supplementary material, which is available to authorized users.

Background Leishmaniasis is a neglected tropical disease with diverse clinical phenotypes, determined by parasite, host and vector interactions. Despite the advances in molecular biology and the availability of more Leishmania genome references in recent years, the association between parasite species and distinct clinical phenotypes remains poorly understood. We present a genomic comparison of an atypical variant of Leishmania donovani from a South Asian focus, where it mostly causes cutaneous form of leishmaniasis. Results Clinical isolates from six cutaneous leishmaniasis patients (CL-SL); 2 of whom were poor responders to antimony (CL-PR), and two visceral leishmaniasis patients (VL-SL) were sequenced on an Illumina MiSeq platform. Chromosome aneuploidy was observed in both groups but was more frequent in CL-SL. 248 genes differed by 2 fold or more in copy number among the two groups. Genes involved in amino acid use (LdBPK_271940) and energy metabolism (LdBPK_271950), predominated the VL-SL group with the same distribution pattern reflected in gene tandem arrays. Genes encoding amastins were present in higher copy numbers in VL-SL and CL-PR as well as being among predicted pseudogenes in CL-SL. Both chromosome and SNP profiles showed CL-SL and VL-SL to form two distinct groups. While expected heterozygosity was much higher in VL-SL, SNP allele frequency patterns did not suggest potential recent recombination breakpoints. The SNP/indel profile obtained using the more recently generated PacBio sequence did not vary markedly from that based on the standard LdBPK282A1 reference. Several genes previously associated with resistance to antimonials were observed in higher copy numbers in the analysis of CL-PR. H-locus amplification was seen in one cutaneous isolate which however did not belong to the CL-PR group. Conclusions The data presented suggests that intra species variations at chromosome and gene level are more likely to influence differences in tropism as well as response to treatment, and contributes to greater understanding of parasite molecular mechanisms underpinning these differences. These findings should be substantiated with a larger sample number and expression/functional studies. Electronic supplementary material The online version of this article (10.1186/s12864-018-5271-z) contains supplementary material, which is available to authorized users.

Background During the evolution of mammalian sex chromosomes, the degeneration of Y-linked homologs has led to a dosage imbalance between X-linked and autosomal genes. The evolutionary resolution to such dosage imbalance, as hypothesized by Susumu Ohno fifty years ago, should be doubling the expression of X-linked genes. Recent studies have nevertheless shown that the X to autosome expression ratio equals ~ 1 in haploid human parthenogenetic embryonic stem (pES) cells and ~ 0.5 in diploid pES cells, suggesting no doubled expression for X-linked genes and refuting Ohno’s hypothesis. Results Here, by reanalyzing an RNA-seq-based single-cell transcriptome dataset of human embryos, we found that from the 8-cell stage until the time-point just prior to implantation, the expression levels of X-linked genes are not two-fold upregulated in male cells and gradually decrease from two-fold in female cells. Additional analyses of gene expression noise further suggest that the dosage sensitivity of X-linked genes is weaker than that of autosomal genes in differentiated female cells, which contradicts a key assumption in Ohno’s hypothesis, that most X-linked genes are dosage sensitive. Moreover, the dosage-sensitive housekeeping genes are preferentially located on autosomes, implying selection against X-linkage for dosage-sensitive genes. Conclusions We observed dosage imbalance between X-linked and autosomal genes, as well as relatively high expression noise from X-linked genes. These results collectively suggest that X-linked genes are less dosage sensitive than autosomal genes, putting one primary assumption of Ohno’s hypothesis in question. Electronic supplementary material The online version of this article (10.1186/s12864-019-5432-8) contains supplementary material, which is available to authorized users.

Background Deciphering the genetic architecture of a species is a good way to understand its evolutionary history, but also to tailor its profile for breeding elite cultivars with desirable traits. Aligning QTLs from diverse population in one map and utilizing it for comparison, but also as a basis for multiple analyses assure a stronger evidence to understand the genetic system related to a given phenotype. Results In this study, 439 genes involved in fatty acid (FA) and triacylglycerol (TAG) biosyntheses were identified in Brassica napus. B. napus genome showed mixed gene loss and insertion compared to B. rapa and B. oleracea, and C genome had more inserted genes. Identified QTLs for oil (OC-QTLs) and fatty acids (FA-QTLs) from nine reported populations were projected on the physical map of the reference genome “Darmor-bzh” to generate a map. Thus, 335 FA-QTLs and OC-QTLs could be highlighted and 82 QTLs were overlapping. Chromosome C3 contained 22 overlapping QTLs with all trait studied except for C18:3. In total, 218 candidate genes which were potentially involved in FA and TAG were identified in 162 QTLs confidence intervals and some of them might affect many traits. Also, 76 among these candidate genes were found inside 57 overlapping QTLs, and candidate genes for oil content were in majority (61/76 genes). Then, sixteen genes were found in overlapping QTLs involving three populations, and the remaining 60 genes were found in overlapping QTLs of two populations. Interaction network and pathway analysis of these candidate genes indicated ten genes that might have strong influence over the other genes that control fatty acids and oil formation. Conclusion The present results provided new information for genetic basis of FA and TAG formation in B. napus. A map including QTLs from numerous populations was built, which could serve as reference to study the genome profile of B. napus, and new potential genes emerged which might affect seed oil. New useful tracks were showed for the selection of population or/and selection of interesting genes for breeding improvement purpose. Electronic supplementary material The online version of this article (10.1186/s12864-017-4176-6) contains supplementary material, which is available to authorized users.

Background Sugarcane (Saccharum spp.) is predominantly an autopolyploid plant with a variable ploidy level, frequent aneuploidy and a large genome that hampers investigation of its organization. Genetic architecture studies are important for identifying genomic regions associated with traits of interest. However, due to the genetic complexity of sugarcane, the practical applications of genomic tools have been notably delayed in this crop, in contrast to other crops that have already advanced to marker-assisted selection (MAS) and genomic selection. High-throughput next-generation sequencing (NGS) technologies have opened new opportunities for discovering molecular markers, especially single nucleotide polymorphisms (SNPs) and insertion-deletion (indels), at the genome-wide level. The objectives of this study were to (i) establish a pipeline for identifying variants from genotyping-by-sequencing (GBS) data in sugarcane, (ii) construct an integrated genetic map with GBS-based markers plus target region amplification polymorphisms and microsatellites, (iii) detect QTLs related to yield component traits, and (iv) perform annotation of the sequences that originated the associated markers with mapped QTLs to search putative candidate genes. Results We used four pseudo-references to align the GBS reads. Depending on the reference, from 3,433 to 15,906 high-quality markers were discovered, and half of them segregated as single-dose markers (SDMs) on average. In addition to 7,049 non-redundant SDMs from GBS, 629 gel-based markers were used in a subsequent linkage analysis. Of 7,678 SDMs, 993 were mapped. These markers were distributed throughout 223 linkage groups, which were clustered in 18 homo(eo)logous groups (HGs), with a cumulative map length of 3,682.04 cM and an average marker density of 3.70 cM. We performed QTL mapping of four traits and found seven QTLs. Our results suggest the presence of a stable QTL across locations. Furthermore, QTLs to soluble solid content (BRIX) and fiber content (FIB) traits had markers linked to putative candidate genes. Conclusions This study is the first to report the use of GBS for large-scale variant discovery and genotyping of a mapping population in sugarcane, providing several insights regarding the use of NGS data in a polyploid, non-model species. The use of GBS generated a large number of markers and still enabled ploidy and allelic dosage estimation. Moreover, we were able to identify seven QTLs, two of which had great potential for validation and future use for molecular breeding in sugarcane. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3383-x) contains supplementary material, which is available to authorized users.

Background Polyploidy and hybridization are both recognized as major forces in evolution. Most of our current knowledge about differences in gene regulation in polyploid hybrids comes from plant studies. The gene expression of diverged genomes and regulatory interactions are still unclear in lower vertebrates. Results We generated 229 million cleaned reads (42.23 Gbp) from triploid of maternal grass carp (Ctenopharyngodon idellus, Cyprininae, 2n = 48) × paternal blunt snout bream (Megalobrama amblycephala, Cultrinae, 2n = 48) and their diploid parents using next-generation sequencing. In total, 157,878 contigs were assembled and 15,444 genes were annotated. We examined gene expression level changes among the parents and their triploid offspring. The mechanisms of dosage compensation that reduced triploid expression levels to the diploid state were determined in triploid fish. In this situation, novel gene expression and gene silencing were observed. Then, we established a model to determine the extent and direction of expression level dominance (ELD) and homoeolog expression bias (HEB) based on the relative expression level among the parents and their triploid offspring. Conclusions Our results showed that the genome-wide ELD was biased toward maternal genome in triploid. Extensive alterations in homoeolog expression suggested a combination of regulatory and epigenetic interactions through the transcriptome network. Additionally, the expression patterns of growth genes provided insights into the relationship between the characteristics of growth and underlying mechanisms in triploids. Regulation patterns of triploid state suggest that various expression levels from the initial genomic merger have important roles in adaptation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3424-5) contains supplementary material, which is available to authorized users.

Background The expanding number and global distributions of herbicide resistant weedy species threaten food, fuel, fiber and bioproduct sustainability and agroecosystem longevity. Amongst the most competitive weeds, Amaranthus palmeri S. Wats has rapidly evolved resistance to glyphosate primarily through massive amplification and insertion of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene across the genome. Increased EPSPS gene copy numbers results in higher titers of the EPSPS enzyme, the target of glyphosate, and confers resistance to glyphosate treatment. To understand the genomic unit and mechanism of EPSPS gene copy number proliferation, we developed and used a bacterial artificial chromosome (BAC) library from a highly resistant biotype to sequence the local genomic landscape flanking the EPSPS gene. Results By sequencing overlapping BACs, a 297 kb sequence was generated, hereafter referred to as the “EPSPS cassette.” This region included several putative genes, dense clusters of tandem and inverted repeats, putative helitron and autonomous replication sequences, and regulatory elements. Whole genome shotgun sequencing (WGS) of two biotypes exhibiting high and no resistance to glyphosate was performed to compare genomic representation across the EPSPS cassette. Mapping of sequences for both biotypes to the reference EPSPS cassette revealed significant differences in upstream and downstream sequences relative to EPSPS with regard to both repetitive units and coding content between these biotypes. The differences in sequence may have resulted from a compounded-building mechanism such as repetitive transpositional events. The association of putative helitron sequences with the cassette suggests a possible amplification and distribution mechanism. Flow cytometry revealed that the EPSPS cassette added measurable genomic content. Conclusions The adoption of glyphosate resistant cropping systems in major crops such as corn, soybean, cotton and canola coupled with excessive use of glyphosate herbicide has led to evolved glyphosate resistance in several important weeds. In Amaranthus palmeri, the amplification of the EPSPS cassette, characterized by a complex array of repetitive elements and putative helitron sequences, suggests an adaptive structural genomic mechanism that drives amplification and distribution around the genome. The added genomic content not found in glyphosate sensitive plants may be driving evolution through genome expansion. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3336-4) contains supplementary material, which is available to authorized users.

Background Recent experiments have shown that codon optimality is a major determinant of mRNA stability in Saccharomyces cerevisiae and that this phenomenon may be conserved in Escherichia coli and some metazoans, although work in Neurospora crassa is not consistent with this model. Results We examined the association between codon optimality and mRNA stability in the fission yeast Schizosaccharomyces pombe. Our analysis revealed the following points. First, we observe a genome-wide association between codon optimality and mRNA stability also in S. pombe, suggesting evolutionary conservation of the phenomenon. Second, in both S. pombe and S. cerevisiae, mRNA synthesis rates are also correlated at the genome-wide analysis with codon optimality, suggesting that the long-appreciated association between codon optimality and mRNA abundance is due to regulation of both mRNA synthesis and degradation. However, when we examined correlation of codon optimality and either mRNA half-lives or synthesis rates controlling for mRNA abundance, codon optimality was still positively correlated with mRNA half-lives in S. cerevisiae, but the association was no longer significant for mRNA half-lives in S. pombe or for synthesis rates in either organism. This illustrates how only the pairwise analysis of multiple correlating variables may limit these types of analyses. Finally, in S. pombe, codon optimality is associated with known DNA/RNA sequence motifs that are associated with mRNA production/stability, suggesting these two features have been under similar selective pressures for optimal gene expression. Conclusions Consistent with the emerging body of studies, this study suggests that the association between codon optimality and mRNA stability may be a broadly conserved phenomenon. It also suggests that the association can be explained at least in part by independent adaptations of codon optimality and other transcript features for elevated expression during evolution. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3237-6) contains supplementary material, which is available to authorized users.

Background Epilepsy is genetically complex but common brain disorder of the world affecting millions of people with almost of all age groups. Novel Copy number variations (CNVs) are considered as important reason for the numerous neurodevelopmental disorders along with intellectual disability and epilepsy. DNA array based studies contribute to explain a more severe clinical presentation of the disease but interoperation of many detected CNVs are still challenging. Results In order to study novel CNVs with epilepsy related genes in Saudi family with six affected and two normal individuals with several forms of epileptic seizures, intellectual disability (ID), and minor dysmorphism, we performed the high density whole genome Agilent sure print G3 Hmn CGH 2x 400 K array-CGH chips analysis. Our results showed de novo deletions, duplications and deletion plus duplication on differential chromosomal regions in the affected individuals that were not shown in the normal fathe and normal kids by using Agilent CytoGenomics 3.0.6.6 softwear. Copy number gain were observed in the chromosome 1, 16 and 22 with LCE3C, HPR, GSTT2, GSTTP2, DDT and DDTL genes respectively whereas the deletions observed in the chromosomal regions 8p23-p21 (4303127–4337759) and the potential gene in this region is CSMD1 (OMIM: 612279). Moreover, the array CGH results deletions and duplication were also validated by using primer design of deleted regions utilizing the flanked SNPs using simple PCR and also by using quantitative real time PCR. Conclusions We found some of the de novo deletions and duplication in our study in Saudi family with intellectual disability and epilepsy. Our results suggest that array-CGH should be used as a first line of genetic test for epilepsy except there is a strong indication for a monogenic syndrome. The advanced high through put array-CGH technique used in this study aim to collect the data base and to identify new mechanisms describing epileptic disorder, may help to improve the clinical management of individual cases in decreasing the burden of epilepsy in Saudi Arabia.

Background DNA copy number profiles from microarray and sequencing experiments sometimes contain wave artefacts which may be introduced during sample preparation and cannot be removed completely by existing preprocessing methods. Besides, large derivative log ratio spread (DLRS) of the probes correlating with poor DNA quality is sometimes observed in genome screening experiments and may lead to unreliable copy number profiles. Depending on the extent of these artefacts and the resulting misidentification of copy number alterations/variations (CNA/CNV), it may be desirable to exclude such samples from analyses or to adapt the downstream data analysis strategy accordingly. Results Here, we propose a method to distinguish reliable genomic copy number profiles from those containing heavy wave artefacts and/or large DLRS. We define four features that adequately summarize the copy number profiles for reliability assessment, and train a classifier on a dataset of 1522 copy number profiles from various microarray platforms. The method can be applied to predict the reliability of copy number profiles irrespective of the underlying microarray platform and may be adapted for those sequencing platforms from which copy number estimates could be computed as a piecewise constant signal. Further details can be found at https://github.com/baudisgroup/CNARA. Conclusions We have developed a method for the assessment of genomic copy number profiling data, and suggest to apply the method in addition to and after other state-of-the-art noise correction and quality control procedures. CNARA could be instrumental in improving the assessment of data used for genomic data mining experiments and support the reliable functional attribution of copy number aberrations especially in cancer research. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3074-7) contains supplementary material, which is available to authorized users.

Background The evolution of animal mitochondrial (mt) genomes has resulted in a highly conserved structure: a single compact circular chromosome approximately 14 to 20 kb long. Within the last two decades exceptions to this conserved structure, such as the division of the genome into multiple chromosomes, have been reported in a diverse set of metazoans. We report on the two circle multipartite mt genome of a newly described cyst nematode, Globodera ellingtonae. Results The G. ellingtonae mt genome was found to be comprised of two circles, each larger than any other multipartite circular mt chromosome yet reported, and both were larger than the single mt circle of the model nematode Caenorhabditis elegans. The genetic content of the genome was disproportionately divided between the two circles, although they shared a ~6.5 kb non-coding region. The 17.8 kb circle (mtDNA-I) contained ten protein-coding genes and two tRNA genes, whereas the 14.4 kb circle (mtDNA-II) contained two protein-coding genes, 20 tRNA genes and both rRNA genes. Perhaps correlated with this division of genetic content, the copy number of mtDNA-II was more than four-fold that of mtDNA-I in individual nematodes. The difference in copy number increased between second-stage and fourth-stage juveniles. Conclusions The segregation of gene types to different mt circles in G. ellingtonae could provide benefit by localizing gene functional types to independent transcriptional units. This is the first report of both two-circle and several-circle mt genomes within a single genus. The differential copy number associated with this multipartite mt organization could provide a model system for deconstructing mechanisms regulating mtDNA copy number both in somatic cells and during germline development. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3047-x) contains supplementary material, which is available to authorized users.

Background Transcriptome reconstruction, defined as the identification of all protein isoforms that may be expressed by a gene, is a notably difficult computational task. With real data, the best methods based on RNA-seq data identify barely 21 % of the expressed transcripts. While waiting for algorithms and sequencing techniques to improve — as has been strongly suggested in the literature — it is important to evaluate assisted transcriptome prediction; this is the question of how alternative transcription in one species performs as a predictor of protein isoforms in another relatively close species. Most evidence-based gene predictors use transcripts from other species to annotate a genome, but the predictive power of procedures that use exclusively transcripts from external species has never been quantified. The cornerstone of such an evaluation is the correct identification of pairs of transcripts with the same splicing patterns, called splicing orthologs. Results We propose a rigorous procedural definition of splicing orthologs, based on the identification of all ortholog pairs of splicing sites in the nucleotide sequences, and alignments at the protein level. Using our definition, we compared 24 382 human transcripts and 17 909 mouse transcripts from the highly curated CCDS database, and identified 11 122 splicing orthologs. In prediction mode, we show that human transcripts can be used to infer over 62 % of mouse protein isoforms. When restricting the predictions to transcripts known eight years ago, the percentage grows to 74 %. Using CCDS timestamped releases, we also analyze the evolution of the number of splicing orthologs over the last decade. Conclusions Alternative splicing is now recognized to play a major role in the protein diversity of eukaryotic organisms, but definitions of spliced isoform orthologs are still approximate. Here we propose a definition adapted to the subtle variations of conserved alternative splicing sites, and use it to validate numerous accurate orthologous isoform predictions. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3103-6) contains supplementary material, which is available to authorized users.

Despite the enormous medical impact of cancers and intensive study of their biology, detailed characterization of tumor growth and development remains elusive. This difficulty occurs in large part because of enormous heterogeneity in the molecular mechanisms of cancer progression, both tumor-to-tumor and cell-to-cell in single tumors. Advances in genomic technologies, especially at the single-cell level, are improving the situation, but these approaches are held back by limitations of the biotechnologies for gathering genomic data from heterogeneous cell populations and the computational methods for making sense of those data. One popular way to gain the advantages of whole-genome methods without the cost of single-cell genomics has been the use of computational deconvolution (unmixing) methods to reconstruct clonal heterogeneity from bulk genomic data. These methods, too, are limited by the difficulty of inferring genomic profiles of rare or subtly varying clonal subpopulations from bulk data, a problem that can be computationally reduced to that of reconstructing the geometry of point clouds of tumor samples in a genome space. Here, we present a new method to improve that reconstruction by better identifying subspaces corresponding to tumors produced from mixtures of distinct combinations of clonal subpopulations. We develop a nonparametric clustering method based on medoidshift clustering for identifying subgroups of tumors expected to correspond to distinct trajectories of evolutionary progression. We show on synthetic and real tumor copy-number data that this new method substantially improves our ability to resolve discrete tumor subgroups, a key step in the process of accurately deconvolving tumor genomic data and inferring clonal heterogeneity from bulk data.

Background Gene copy-number variation (CNVs), which provides the raw material for the evolution of novel genes, is widespread in natural populations. We investigated whether CNVs constitute a common mechanism of genetic change during adaptation in experimental Caenorhabditis elegans populations. Outcrossing C. elegans populations with low fitness were evolved for >200 generations. The frequencies of CNVs in these populations were analyzed by oligonucleotide array comparative genome hybridization, quantitative PCR, PCR, DNA sequencing across breakpoints, and single-worm PCR. Results Multiple duplications and deletions rose to intermediate or high frequencies in independent populations. Several lines of evidence suggest that these changes were adaptive: (i) copy-number changes reached high frequency or were fixed in a short time, (ii) many independent populations harbored CNVs spanning the same genes, and (iii) larger average size of CNVs in adapting populations relative to spontaneous CNVs. The latter is expected if larger CNVs are more likely to encompass genes under selection for a change in gene dosage. Several convergent CNVs originated in populations descended from different low fitness ancestors as well as high fitness controls. Conclusions We show that gene copy-number changes are a common class of adaptive genetic change. Due to the high rates of origin of spontaneous duplications and deletions, copy-number changes containing the same genes arose readily in independent populations. Duplications that reached high frequencies in these adapting populations were significantly larger in span. Many convergent CNVs may be general adaptations to laboratory conditions. These results demonstrate the great potential borne by CNVs for evolutionary adaptation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2253-2) contains supplementary material, which is available to authorized users.

Background Several statistical tools have been developed to identify genes mutated at rates significantly higher than background, indicative of positive selection, involving large sample cohort studies. However, studies involving smaller sample sizes are inherently restrictive due to their limited statistical power to identify low frequency genetic variations. Results We performed an integrated characterization of copy number, mutation and expression analyses of four head and neck cancer cell lines - NT8e, OT9, AW13516 and AW8507-- by applying a filtering strategy to prioritize for genes affected by two or more alterations within or across the cell lines. Besides identifying TP53, PTEN, HRAS and MET as major altered HNSCC hallmark genes, this analysis uncovered 34 novel candidate genes altered. Of these, we find a heterozygous truncating mutation in Nuclear receptor binding protein, NRBP1 pseudokinase gene, identical to as reported in other cancers, is oncogenic when ectopically expressed in NIH-3 T3 cells. Knockdown of NRBP1 in an oral carcinoma cell line bearing NRBP1 mutation inhibit transformation and survival of the cells. Conclusions In overall, we present the first comprehensive genomic characterization of four head and neck cancer cell lines established from Indian patients. We also demonstrate the ability of integrated analysis to uncover biologically important genetic variation in studies involving fewer or rare clinical specimens. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2138-4) contains supplementary material, which is available to authorized users.

Background Gene regulatory relationships can be inferred using matched array comparative genomics and transcriptomics data sets from cancer samples. The way in which copy numbers of genes in cancer samples are often greatly disrupted works like a natural gene amplification/deletion experiment. There are now a large number of such data sets publicly available making a meta-analysis of the data possible. Results We infer inter-chromosomal acting gene regulatory relationships from a meta-analysis of 31 publicly available matched array comparative genomics and transcriptomics data sets in humans. We obtained statistically significant predictions of target genes for 1430 potential regulatory genes. The regulatory relationships being inferred are either direct relationships, of a transcription factor on its target, or indirect ones, through pathways containing intermediate steps. We analyse the predictions in terms of cocitations, both publications which cite a regulator with any of its inferred targets and cocitations of any genes in a target list. Conclusions The most striking observation from the results is the greater number of inter-chromosomal regulatory relationships involving repression compared to those involving activation. The complete results of the meta-analysis are presented in the database METAMATCHED. We anticipate that the predictions contained in the database will be useful in informing experiments and in helping to construct networks of regulatory relationships. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2100-5) contains supplementary material, which is available to authorized users.

Background The development of a more refined prognostic methodology for early non-small cell lung cancer (NSCLC) is an unmet clinical need. An accurate prognostic tool might help to select patients at early stages for adjuvant therapies. Results A new integrated bioinformatics searching strategy, that combines gene copy number alterations and expression, together with clinical parameters was applied to derive two prognostic genomic signatures. The proposed methodology combines data from patients with and without clinical data with a priori information on the ability of a gene to be a prognostic marker. Two initial candidate sets of 513 and 150 genes for lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC), respectively, were generated by identifying genes which have both: a) significant correlation between copy number and gene expression, and b) significant prognostic value at the gene expression level in external databases. From these candidates, two panels of 7 (ADC) and 5 (SCC) genes were further identified via semi-supervised learning. These panels, together with clinical data (stage, age and sex), were used to construct the ADC and SCC hazard scores combining clinical and genomic data. The signatures were validated in two independent datasets (n = 73 for ADC, n = 97 for SCC), confirming that the prognostic value of both clinical-genomic models is robust, statistically significant (P = 0.008 for ADC and P = 0.019 for SCC) and outperforms both the clinical models (P = 0.060 for ADC and P = 0.121 for SCC) and the genomic models applied separately (P = 0.350 for ADC and P = 0.269 for SCC). Conclusion The present work provides a methodology to generate a robust signature using copy number data that can be potentially used to any cancer. Using it, we found new prognostic scores based on tumor DNA that, jointly with clinical information, are able to predict overall survival (OS) in patients with early-stage ADC and SCC. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1935-0) contains supplementary material, which is available to authorized users.

Background Over the course of its intraerythrocytic developmental cycle (IDC), the malaria parasite Plasmodium falciparum tightly orchestrates the rise and fall of transcript levels for hundreds of genes. Considerable debate has focused on the relative importance of transcriptional versus post-transcriptional processes in the regulation of transcript levels. Enzymatically active forms of RNAPII in other organisms have been associated with phosphorylation on the serines at positions 2 and 5 of the heptad repeats within the C-terminal domain (CTD) of RNAPII. We reasoned that insight into the contribution of transcriptional mechanisms to gene expression in P. falciparum could be obtained by comparing the presence of enzymatically active forms of RNAPII at multiple genes with the abundance of their associated transcripts. Results We exploited the phosphorylation state of the CTD to detect enzymatically active forms of RNAPII at most P. falciparum genes across the IDC. We raised highly specific monoclonal antibodies against three forms of the parasite CTD, namely unphosphorylated, Ser5-P and Ser2/5-P, and used these in ChIP-on-chip type experiments to map the genome-wide occupancy of RNAPII. Our data reveal that the IDC is divided into early and late phases of RNAPII occupancy evident from simple bi-phasic RNAPII binding profiles. By comparison to mRNA abundance, we identified sub-sets of genes with high occupancy by enzymatically active forms of RNAPII and relatively low transcript levels and vice versa. We further show that the presence of active and repressive histone modifications correlates with RNAPII occupancy over the IDC. Conclusions The simple early/late occupancy by RNAPII cannot account for the complex dynamics of mRNA accumulation over the IDC, suggesting a major role for mechanisms acting downstream of RNAPII occupancy in the control of gene expression in this parasite. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-959) contains supplementary material, which is available to authorized users.

Background Previous work on whole genome doubling in plants established the importance of gene functional category in provoking or suppressing duplicate gene loss, or fractionation. Other studies, particularly in Paramecium have correlated levels of gene expression with vulnerability or resistance to duplicate loss. Results Here we analyze the simultaneous effect of function category and expression in two plant data sets, rosids and asterids. Conclusion We demonstrate function category and expression level have independent effects, though expression does not play the dominant role it does in Paramecium.

Background Micro (mi)RNAs are important regulators of plant development. Across plant lineages, Dicer-like 1 (DCL1) proteins process long ds-like structures to produce micro (mi) RNA duplexes in a stepwise manner. These miRNAs are incorporated into Argonaute (AGO) proteins and influence expression of RNAs that have sequence complementarity with miRNAs. Expression levels of AGOs are greatly regulated by plants in order to minimize unwarranted perturbations using miRNAs to target mRNAs coding for AGOs. AGOs may also have high promoter specificity-sometimes expression of AGO can be limited to just a few cells in a plant. Viral pathogens utilize various means to counter antiviral roles of AGOs including hijacking the host encoded miRNAs to target AGOs. Two host encoded miRNAs namely miR168 and miR403 that target AGOs have been described in the model plant Arabidopsis and such a mechanism is thought to be well conserved across plants because AGO sequences are well conserved. Results We show that the interaction between AGO mRNAs and miRNAs is species-specific due to the diversity in sequences of two miRNAs that target AGOs, sequence diversity among corresponding target regions in AGO mRNAs and variable expression levels of these miRNAs among vascular plants. We used miRNA sequences from 68 plant species representing 31 plant families for this analysis. Sequences of miR168 and miR403 are not conserved among plant lineages, but surprisingly they differ drastically in their sequence diversity and expression levels even among closely related plants. Variation in miR168 expression among plants correlates well with secondary structures/length of loop sequences of their precursors. Conclusions Our data indicates a complex AGO targeting interaction among plant lineages due to miRNA sequence diversity and sequences of miRNA targeting regions among AGO mRNAs, thus leading to the assumption that the perturbations by viruses that use host miRNAs to target antiviral AGOs can only be species-specific. We also show that rapid evolution and likely loss of expression of miR168 isoforms in tobacco is related to the insertion of MITE-like transposons between miRNA and miRNA* sequences, a possible mechanism showing how miRNAs are lost in few plant lineages even though other close relatives have abundantly expressing miRNAs. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1049) contains supplementary material, which is available to authorized users.

Background The homeodomain leucine zipper (HD-Zip) transcription factor family is one of the largest plant specific superfamilies, and includes genes with roles in modulation of plant growth and response to environmental stresses. Many HD-Zip genes are characterized in Arabidopsis (Arabidopsis thaliana), and members of the family are being investigated for abiotic stress responses in rice (Oryza sativa), maize (Zea mays), poplar (Populus trichocarpa) and cucumber (Cucmis sativus). Findings in these species suggest HD-Zip genes as high priority candidates for crop improvement. Results In this study we have identified members of the HD-Zip gene family in soybean cv. ‘Williams 82’, and characterized their expression under dehydration and salt stress. Homology searches with BLASTP and Hidden Markov Model guided sequence alignments identified 101 HD-Zip genes in the soybean genome. Phylogeny reconstruction coupled with domain and gene structure analyses using soybean, Arabidopsis, rice, grape (Vitis vinifera), and Medicago truncatula homologues enabled placement of these sequences into four previously described subfamilies. Of the 101 HD-Zip genes identified in soybean, 88 exist as whole-genome duplication-derived gene pairs, indicating high retention of these genes following polyploidy in Glycine ~13 Mya. The HD-Zip genes exhibit ubiquitous expression patterns across 24 conditions that include 17 tissues of soybean. An RNA-Seq experiment performed to study differential gene expression at 0, 1, 6 and 12 hr soybean roots under dehydration and salt stress identified 20 differentially expressed (DE) genes. Several of these DE genes are orthologs of genes previously reported to play a role under abiotic stress, implying conservation of HD-Zip gene functions across species. Screening of HD-Zip promoters identified transcription factor binding sites that are overrepresented in the DE genes under both dehydration and salt stress, providing further support for the role of HD-Zip genes in abiotic stress responses. Conclusions We provide a thorough description of soybean HD-Zip genes, and identify potential candidates with probable roles in dehydration and salt stress. Expression profiles generated for all soybean genes, under dehydration and salt stress, at four time points, will serve as an important resource for the soybean research community, and will aid in understanding plant responses to abiotic stress. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-950) contains supplementary material, which is available to authorized users.

Background Despite having predominately deleterious fitness effects, transposable elements (TEs) are major constituents of eukaryote genomes in general and of plant genomes in particular. Although the proportion of the genome made up of TEs varies at least four-fold across plants, the relative importance of the evolutionary forces shaping variation in TE abundance and distributions across taxa remains unclear. Under several theoretical models, mating system plays an important role in governing the evolutionary dynamics of TEs. Here, we use the recently sequenced Capsella rubella reference genome and short-read whole genome sequencing of multiple individuals to quantify abundance, genome distributions, and population frequencies of TEs in three recently diverged species of differing mating system, two self-compatible species (C. rubella and C. orientalis) and their self-incompatible outcrossing relative, C. grandiflora. Results We detect different dynamics of TE evolution in our two self-compatible species; C. rubella shows a small increase in transposon copy number, while C. orientalis shows a substantial decrease relative to C. grandiflora. The direction of this change in copy number is genome wide and consistent across transposon classes. For insertions near genes, however, we detect the highest abundances in C. grandiflora. Finally, we also find differences in the population frequency distributions across the three species. Conclusion Overall, our results suggest that the evolution of selfing may have different effects on TE evolution on a short and on a long timescale. Moreover, cross-species comparisons of transposon abundance are sensitive to reference genome bias, and efforts to control for this bias are key when making comparisons across species. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-602) contains supplementary material, which is available to authorized users.

Background Single copy genes are common across angiosperm genomes. With the sufficiently high quality sequenced genomes, the identification of large-scale single copy genes among multiple species is possible. Although some characteristics have been reported, our study provides novel insights into single copy genes. Results We identified single copy genes across 29 angiosperm genomes. A significant negative correlation was found between the number of duplicate blocks and the number of single copy genes. We found that a considerable number of single copy genes are located in organelles, showing a preference for binding and catalytic activity. The analysis of effective number of codons (Nc) illustrates that single copy genes have a stronger codon bias than non-single copy genes in eudicots. The relative high expression level of single copy genes was partially confirmed by the RNA-seq data, rather than the Codon Adaptation Index (CAI). Unlike in most other species, a strongly negatively correlation occurs between Nc and GC3 among single copy genes in grass genomes. When compared to all non-single copy genes, single copy genes indicate more conservation (as indicated by Ka and Ks values). But our alternative splicing (AS) results reveal that selective constraints are weaker in single copy genes than in low copy family genes (1–10 in-paralogs) and stronger than high copy family genes (>10 in-paralogs). Using concatenated shared single copy genes, we obtained a well-resolved phylogenetic tree. With the addition of intron sequences, the branch support is improved, but striking incongruences are also evident. Therefore, it is noteworthy that inclusion of intron sequences seems more appropriate for the phylogenetic reconstruction at lower taxonomic levels. Conclusions Our analysis provides insight into the evolutionary characteristics of single copy genes across 29 angiosperm genomes. The results suggest that there are key differences in evolutionary constraints between single copy genes and non-single copy genes. And to some extent, these evolutionary constraints show some species-specific differences, especially between eudicots and monocots. Our preliminary evidence also suggests that the concatenated shared single copy genes are well suited for use in resolving phylogenetic relationships. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-504) contains supplementary material, which is available to authorized users.

Background Gene duplication is a source of evolutionary innovation and can contribute to the divergence of lineages; however, the relative importance of this process remains to be determined. The explosive divergence of the African cichlid adaptive radiations provides both a model for studying the general role of gene duplication in the divergence of lineages and also an exciting foray into the identification of genomic features that underlie the dramatic phenotypic and ecological diversification in this particular lineage. We present the first genome-wide study of gene duplication in African cichlid fishes, identifying gene duplicates in three species belonging to the Lake Malawi adaptive radiation (Metriaclima estherae, Protomelas similis, Rhamphochromis “chilingali”) and one closely related species from a non-radiated riverine lineage (Astatotilapia tweddlei). Results Using Astatotilapia burtoni as reference, microarray comparative genomic hybridization analysis of 5689 genes reveals 134 duplicated genes among the four cichlid species tested. Between 51 and 55 genes were identified as duplicated in each of the three species from the Lake Malawi radiation, representing a 38%–49% increase in number of duplicated genes relative to the non-radiated lineage (37 genes). Duplicated genes include several that are involved in immune response, ATP metabolism and detoxification. Conclusions These results contribute to our understanding of the abundance and type of gene duplicates present in cichlid fish lineages. The duplicated genes identified in this study provide candidates for the analysis of functional relevance with regard to phenotype and divergence. Comparative sequence analysis of gene duplicates can address the role of positive selection and adaptive evolution by gene duplication, while further study across the phylogenetic range of cichlid radiations (and more generally in other adaptive radiations) will determine whether the patterns of gene duplication seen in this study consistently accompany rapid radiation.

Background Copy number variations (CNVs) confer significant effects on genetic innovation and phenotypic variation. Previous CNV studies in swine seldom focused on in-depth characterization of global CNVs. Results Using whole-genome assembly comparison (WGAC) and whole-genome shotgun sequence detection (WSSD) approaches by next generation sequencing (NGS), we probed formation signatures of both segmental duplications (SDs) and individualized CNVs in an integrated fashion, building the finest resolution CNV and SD maps of pigs so far. We obtained copy number estimates of all protein-coding genes with copy number variation carried by individuals, and further confirmed two genes with high copy numbers in Meishan pigs through an enlarged population. We determined genome-wide CNV hotspots, which were significantly enriched in SD regions, suggesting evolution of CNV hotspots may be affected by ancestral SDs. Through systematically enrichment analyses based on simulations and bioinformatics analyses, we revealed CNV-related genes undergo a different selective constraint from those CNV-unrelated regions, and CNVs may be associated with or affect pig health and production performance under recent selection. Conclusions Our studies lay out one way for characterization of CNVs in the pig genome, provide insight into the pig genome variation and prompt CNV mechanisms studies when using pigs as biomedical models for human diseases. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-593) contains supplementary material, which is available to authorized users.

Background Killer Immunoglobulin-like Receptors (KIRs) are surface receptors of natural killer cells that bind to their corresponding Human Leukocyte Antigen (HLA) class I ligands, making them interesting candidate genes for HLA-associated autoimmune diseases, including type 1 diabetes (T1D). However, allelic and copy number variation in the KIR region effectively mask it from standard genome-wide association studies: single nucleotide polymorphism (SNP) probes targeting the region are often discarded by standard genotype callers since they exhibit variable cluster numbers. Quantitative Polymerase Chain Reaction (qPCR) assays address this issue. However, their cost is prohibitive at the sample sizes required for detecting effects typically observed in complex genetic diseases. Results We propose a more powerful and cost-effective alternative, which combines signals from SNPs with more than three clusters found in existing datasets, with qPCR on a subset of samples. First, we showed that noise and batch effects in multiplexed qPCR assays are addressed through normalisation and simultaneous copy number calling of multiple genes. Then, we used supervised classification to impute copy numbers of specific KIR genes from SNP signals. We applied this method to assess copy number variation in two KIR genes, KIR3DL1 and KIR3DS1, which are suitable candidates for T1D susceptibility since they encode the only KIR molecules known to bind with HLA-Bw4 epitopes. We find no association between KIR3DL1/3DS1 copy number and T1D in 6744 cases and 5362 controls; a sample size twenty-fold larger than in any previous KIR association study. Due to our sample size, we can exclude odds ratios larger than 1.1 for the common KIR3DL1/3DS1 copy number groups at the 5% significance level. Conclusion We found no evidence of association of KIR3DL1/3DS1 copy number with T1D, either overall or dependent on HLA-Bw4 epitope. Five other KIR genes, KIR2DS4, KIR2DL3, KIR2DL5, KIR2DS5 and KIR2DS1, in high linkage disequilibrium with KIR3DL1 and KIR3DS1, are also unlikely to be significantly associated. Our approach could potentially be applied to other KIR genes to allow cost effective assaying of gene copy number in large samples.

Background Aluminum (Al) toxicity is an important limitation to food security in tropical and subtropical regions. High Al saturation on acid soils limits root development, reducing water and nutrient uptake. In addition to naturally occurring acid soils, agricultural practices may decrease soil pH, leading to yield losses due to Al toxicity. Elucidating the genetic and molecular mechanisms underlying maize Al tolerance is expected to accelerate the development of Al-tolerant cultivars. Results Five genomic regions were significantly associated with Al tolerance, using 54,455 SNP markers in a recombinant inbred line population derived from Cateto Al237. Candidate genes co-localized with Al tolerance QTLs were further investigated. Near-isogenic lines (NILs) developed for ZmMATE2 were as Al-sensitive as the recurrent line, indicating that this candidate gene was not responsible for the Al tolerance QTL on chromosome 5, qALT5. However, ZmNrat1, a maize homolog to OsNrat1, which encodes an Al3+ specific transporter previously implicated in rice Al tolerance, was mapped at ~40 Mbp from qALT5. We demonstrate for the first time that ZmNrat1 is preferentially expressed in maize root tips and is up-regulated by Al, similarly to OsNrat1 in rice, suggesting a role of this gene in maize Al tolerance. The strongest-effect QTL was mapped on chromosome 6 (qALT6), within a 0.5 Mbp region where three copies of the Al tolerance gene, ZmMATE1, were found in tandem configuration. qALT6 was shown to increase Al tolerance in maize; the qALT6-NILs carrying three copies of ZmMATE1 exhibited a two-fold increase in Al tolerance, and higher expression of ZmMATE1 compared to the Al sensitive recurrent parent. Interestingly, a new source of Al tolerance via ZmMATE1 was identified in a Brazilian elite line that showed high expression of ZmMATE1 but carries a single copy of ZmMATE1. Conclusions High ZmMATE1 expression, controlled either by three copies of the target gene or by an unknown molecular mechanism, is responsible for Al tolerance mediated by qALT6. As Al tolerant alleles at qALT6 are rare in maize, marker-assisted introgression of this QTL is an important strategy to improve maize adaptation to acid soils worldwide. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-153) contains supplementary material, which is available to authorized users.

Background Divergence in gene structure following gene duplication is not well understood. Gene duplication can occur via whole-genome duplication (WGD) and single-gene duplications including tandem, proximal and transposed duplications. Different modes of gene duplication may be associated with different types, levels, and patterns of structural divergence. Results In Arabidopsis thaliana, we denote levels of structural divergence between duplicated genes by differences in coding-region lengths and average exon lengths, and the number of insertions/deletions (indels) and maximum indel length in their protein sequence alignment. Among recent duplicates of different modes, transposed duplicates diverge most dramatically in gene structure. In transposed duplications, parental loci tend to have longer coding-regions and exons, and smaller numbers of indels and maximum indel lengths than transposed loci, reflecting biased structural changes in transposed duplications. Structural divergence increases with evolutionary time for WGDs, but not transposed duplications, possibly because of biased gene losses following transposed duplications. Structural divergence has heterogeneous relationships with nucleotide substitution rates, but is consistently positively correlated with gene expression divergence. The NBS-LRR gene family shows higher-than-average levels of structural divergence. Conclusions Our study suggests that structural divergence between duplicated genes is greatly affected by the mechanisms of gene duplication and may be not proportional to evolutionary time, and that certain gene families are under selection on rapid evolution of gene structure.

BackgroundChromatin diminution is the programmed deletion of DNA from presomatic cell or nuclear lineages during development, producing single organisms that contain two different nuclear genomes. Phylogenetically diverse taxa undergo chromatin diminution — some ciliates, nematodes, copepods, and vertebrates. In cyclopoid copepods, chromatin diminution occurs in taxa with massively expanded germline genomes; depending on species, germline genome sizes range from 15 – 75 Gb, 12–74 Gb of which are lost from pre-somatic cell lineages at germline – soma differentiation. This is more than an order of magnitude more sequence than is lost from other taxa. To date, the sequences excised from copepods have not been analyzed using large-scale genomic datasets, and the processes underlying germline genomic gigantism in this clade, as well as the functional significance of chromatin diminution, have remained unknown.ResultsHere, we used high-throughput genomic sequencing and qPCR to characterize the germline and somatic genomes ofMesocyclops edax, a freshwater cyclopoid copepod with a germline genome of ~15 Gb and a somatic genome of ~3 Gb. We show that most of the excised DNA consists of repetitive sequences that are either 1) verifiable transposable elements (TEs), or 2) non-simple repeats of likely TE origin. Repeat elements in both genomes are skewed towards younger (i.e. less divergent) elements. Excised DNA is a non-random sample of the germline repeat element landscape; younger elements, and high frequency DNA transposons and LINEs, are disproportionately eliminated from the somatic genome.ConclusionsOur results suggest that germline genome expansion inM. edaxreflects explosive repeat element proliferation, and that billions of base pairs of such repeats are deleted from the somatic genome every generation. Thus, we hypothesize that chromatin diminution is a mechanism that controls repeat element load, and that this load can evolve to be divergent between tissue types within single organisms.

Background Cancer progression is associated with genomic instability and an accumulation of gains and losses of DNA. The growing variety of tools for measuring genomic copy numbers, including various types of array-CGH, SNP arrays and high-throughput sequencing, calls for a coherent framework offering unified and consistent handling of single- and multi-track segmentation problems. In addition, there is a demand for highly computationally efficient segmentation algorithms, due to the emergence of very high density scans of copy number. Results A comprehensive Bioconductor package for copy number analysis is presented. The package offers a unified framework for single sample, multi-sample and multi-track segmentation and is based on statistically sound penalized least squares principles. Conditional on the number of breakpoints, the estimates are optimal in the least squares sense. A novel and computationally highly efficient algorithm is proposed that utilizes vector-based operations in R. Three case studies are presented. Conclusions The R package is a software suite for segmentation of single- and multi-track copy number data using algorithms based on coherent least squares principles.

Background Actinoplanes sp. SE50/110 is known as the wild type producer of the alpha-glucosidase inhibitor acarbose, a potent drug used worldwide in the treatment of type-2 diabetes mellitus. As the incidence of diabetes is rapidly rising worldwide, an ever increasing demand for diabetes drugs, such as acarbose, needs to be anticipated. Consequently, derived Actinoplanes strains with increased acarbose yields are being used in large scale industrial batch fermentation since 1990 and were continuously optimized by conventional mutagenesis and screening experiments. This strategy reached its limits and is generally superseded by modern genetic engineering approaches. As a prerequisite for targeted genetic modifications, the complete genome sequence of the organism has to be known. Results Here, we present the complete genome sequence of Actinoplanes sp. SE50/110 [GenBank:CP003170], the first publicly available genome of the genus Actinoplanes, comprising various producers of pharmaceutically and economically important secondary metabolites. The genome features a high mean G + C content of 71.32% and consists of one circular chromosome with a size of 9,239,851 bp hosting 8,270 predicted protein coding sequences. Phylogenetic analysis of the core genome revealed a rather distant relation to other sequenced species of the family Micromonosporaceae whereas Actinoplanes utahensis was found to be the closest species based on 16S rRNA gene sequence comparison. Besides the already published acarbose biosynthetic gene cluster sequence, several new non-ribosomal peptide synthetase-, polyketide synthase- and hybrid-clusters were identified on the Actinoplanes genome. Another key feature of the genome represents the discovery of a functional actinomycete integrative and conjugative element. Conclusions The complete genome sequence of Actinoplanes sp. SE50/110 marks an important step towards the rational genetic optimization of the acarbose production. In this regard, the identified actinomycete integrative and conjugative element could play a central role by providing the basis for the development of a genetic transformation system for Actinoplanes sp. SE50/110 and other Actinoplanes spp. Furthermore, the identified non-ribosomal peptide synthetase- and polyketide synthase-clusters potentially encode new antibiotics and/or other bioactive compounds, which might be of pharmacologic interest.

Background As a newly identified category of DNA transposon, helitrons have been found in a large number of eukaryotes genomes. Helitrons have contributed significantly to the intra-specific genome diversity in maize. Although many characteristics of helitrons in the maize genome have been well documented, the sequence of an intact autonomous helitrons has not been identified in maize. In addition, the process of gene fragment capturing during the transposition of helitrons has not been characterized. Results The whole genome sequences of maize inbred line B73 were analyzed, 1,649 helitron-like transposons including 1,515 helAs and 134 helBs were identified. ZmhelA1, ZmhelB1 and ZmhelB2 all encode an open reading frame (ORF) with intact replication initiator (Rep) motif and a DNA helicase (Hel) domain, which are similar to previously reported autonomous helitrons in other organisms. The putative autonomous ZmhelB1 and ZmhelB2 contain an extra replication factor-a protein1 (RPA1) transposase (RPA-TPase) including three single strand DNA-binding domains (DBD)-A/-B/-C in the ORF. Over ninety percent of maize helitrons identified have captured gene fragments. HelAs and helBs carry 4,645 and 249 gene fragments, which yield 2,507 and 187 different genes respectively. Many helitrons contain mutilple terminal sequences, but only one 3'-terminal sequence had an intact "CTAG" motif. There were no significant differences in the 5'-termini sequence between the veritas terminal sequence and the pseudo sequence. Helitrons not only can capture fragments, but were also shown to lose internal sequences during the course of transposing. Conclusions Three putative autonomous elements were identified, which encoded an intact Rep motif and a DNA helicase domain, suggesting that autonomous helitrons may exist in modern maize. The results indicate that gene fragments captured during the transposition of many helitrons happen in a stepwise way, with multiple gene fragments within one helitron resulting from several sequential transpositions. In addition, we have proposed a potential mechanism regarding how helitrons with multiple termini are generated.

Background Copy neutral loss of heterozygosity (CN-LOH) refers to a special case of LOH occurring without any resulting loss in copy number. These alterations is sometimes seen in tumors as a way to inactivate a tumor suppressor gene and have been found to be important in several types of cancer. Results We have used high density single nucleotide polymorphism arrays in order to investigate the frequency and distribution of CN-LOH and other allelic imbalances in neuroblastoma (NB) tumors and cell lines. Our results show that the frequency of these near-CN-LOH events is significantly higher in the cell lines compared to the primary tumors and that the types of CN-LOH differ between the groups. We also show that the low-risk neuroblastomas that are generally considered to have a "triploid karyotype" often present with a complex numerical karyotype (no segmental changes) with 2-5 copies of each chromosome. Furthermore a comparison has been made between the three related cell lines SK-N-SH, SH-EP and SH-SY5Y with respect to overall genetic aberrations, and several aberrations unique to each of the cell lines has been found. Conclusions We have shown that the NB tumors analyzed contain several interesting allelic imbalances that would either go unnoticed or be misinterpreted using other genome-wide techniques. These findings indicate that the genetics underlying NB might be even more complex than previously known and that SNP arrays are important analysis tools. We have also showed that these near-CN-LOH events are more frequently seen in NB cell lines compared to NB tumors and that a set of highly related cell lines have continued to evolve secondary to the subcloning event. Taken together our analysis highlights that cell lines in many cases differ substantially from the primary tumors they are thought to represent, and that caution should be taken when drawing conclusions from cell line-based studies.

Background Copy number variations (CNVs) can create new genes, change gene dosage, reshape gene structures, and modify elements regulating gene expression. As with all types of genetic variation, CNVs may influence phenotypic variation and gene expression. CNVs are thus considered major sources of genetic variation. Little is known, however, about their contribution to genetic variation in rice. Results To detect CNVs, we used a set of NimbleGen whole-genome comparative genomic hybridization arrays containing 718,256 oligonucleotide probes with a median probe spacing of 500 bp. We compiled a high-resolution map of CNVs in the rice genome, showing 641 CNVs between the genomes of the rice cultivars 'Nipponbare' (from O. sativa ssp. japonica) and 'Guang-lu-ai 4' (from O. sativa ssp. indica). The CNVs identified vary in size from 1.1 kb to 180.7 kb, and encompass approximately 7.6 Mb of the rice genome. The largest regions showing copy gain and loss are of 37.4 kb on chromosome 4, and 180.7 kb on chromosome 8. In addition, 85 DNA segments were identified, including some genic sequences. Contracted genes greatly outnumbered duplicated ones. Many of the contracted genes corresponded to either the same genes or genes involved in the same biological processes; this was also the case for genes involved in disease and defense. Conclusion We detected CNVs in rice by array-based comparative genomic hybridization. These CNVs contain known genes. Further discussion of CNVs is important, as they are linked to variation among rice varieties, and are likely to contribute to subspecific characteristics.

Background In highly copy number variable (CNV) regions such as the human defensin gene locus, comprehensive assessment of sequence variations is challenging. PCR approaches are practically restricted to tiny fractions, and next-generation sequencing (NGS) approaches of whole individual genomes e.g. by the 1000 Genomes Project is confined by an affordable sequence depth. Combining target enrichment with NGS may represent a feasible approach. Results As a proof of principle, we enriched a ~850 kb section comprising the CNV defensin gene cluster DEFB, the invariable DEFA part and 11 control regions from two genomes by sequence capture and sequenced it by 454 technology. 6,651 differences to the human reference genome were found. Comparison to HapMap genotypes revealed sensitivities and specificities in the range of 94% to 99% for the identification of variations. Using error probabilities for rigorous filtering revealed 2,886 unique single nucleotide variations (SNVs) including 358 putative novel ones. DEFB CN determinations by haplotype ratios were in agreement with alternative methods. Conclusion Although currently labor extensive and having high costs, target enriched NGS provides a powerful tool for the comprehensive assessment of SNVs in highly polymorphic CNV regions of individual genomes. Furthermore, it reveals considerable amounts of putative novel variations and simultaneously allows CN estimation.

Background The mosquito, Anopheles gambiae, is the primary vector of human malaria, a disease responsible for millions of deaths each year. To improve strategies for controlling transmission of the causative parasite, Plasmodium falciparum, we require a thorough understanding of the developmental mechanisms, physiological processes and evolutionary pressures affecting life-history traits in the mosquito. Identifying genes expressed in particular tissues or involved in specific biological processes is an essential part of this process. Results In this study, we present transcription profiles for ~82% of annotated Anopheles genes in dissected adult male and female tissues. The sensitivity afforded by examining dissected tissues found gene activity in an additional 20% of the genome that is undetected when using whole-animal samples. The somatic and reproductive tissues we examined each displayed patterns of sexually dimorphic and tissue-specific expression. By comparing expression profiles with Drosophila melanogaster we also assessed which genes are well conserved within the Diptera versus those that are more recently evolved. Conclusions Our expression atlas and associated publicly available database, the MozAtlas (http://www.tissue-atlas.org), provides information on the relative strength and specificity of gene expression in several somatic and reproductive tissues, isolated from a single strain grown under uniform conditions. The data will serve as a reference for other mosquito researchers by providing a simple method for identifying where genes are expressed in the adult, however, in addition our resource will also provide insights into the evolutionary diversity associated with gene expression levels among species.

Background Repeat-induced point mutation (RIP) is a fungal genome defence mechanism guarding against transposon invasion. RIP mutates the sequence of repeated DNA and over time renders the affected regions unrecognisable by similarity search tools such as BLAST. Results DeRIP is a new software tool developed to predict the original sequence of a RIP-mutated region prior to the occurrence of RIP. In this study, we apply deRIP to the genome of the wheat pathogen Stagonospora nodorum SN15 and predict the origin of several previously uncharacterised classes of repetitive DNA. Conclusions Five new classes of transposon repeats and four classes of endogenous gene repeats were identified after deRIP. The deRIP process is a new tool for fungal genomics that facilitates the identification and understanding of the role and origin of fungal repetitive DNA. DeRIP is open-source and is available as part of the RIPCAL suite at http://www.sourceforge.net/projects/ripcal.