Search

Curvature in mammalian fibers, such as wool and human hair, is an important feature of the functional trait of coat structure—it affects mechanical resilience and thermo‐insulation. However, to examine the relationship between fiber curvature, ultrastructure and protein composition fiber diameter variability has to be minimal. To achieve this we utilised the progeny of straight‐wool domestic sheep mutant rams (crimp mutants) and wild‐type ewes. Proteomic and structural results of the resulting mutant/wild‐type twin pairs confirmed that straight crimp mutant wool had a normal cuticle and the same cortical protein and ultrastructural building blocks as wild‐type (crimpy) fibers but differed in the layout of its cortical cells and in the relative proportions of keratin (K) and keratin‐associated proteins (KAPs). In the case of the crimp mutants (straight fibers), the orthocortex was distributed in a fragmented, annular ring, with some orthocortical cells near the central medulla, a pattern similar to that of straight hairs from humans and other mammals. Crimp mutant fibers were noted for the reduced abundance of some proteins in the high glycine–tyrosine class normally associated with the orthocortex, specifically the KAP6, KAP7, and KAP8 families, while proteins from the KAP16 and KAP19 were found in increased abundance. In addition to this, the type I keratin, K38, which is also associated with the orthocortex, was also found at lower abundance in the mutant fibers. Conversely, proteins from the ultra‐high sulfur class normally associated with the paracortex, specifically the KAP4 and KAP9 families, were found in higher abundance. [ABSTRACT FROM AUTHOR]

Abstract Background F1 hybrid clones of Eucalyptus grandis and E. urophylla are widely grown for pulp and paper production in tropical and subtropical regions. Volume growth and wood quality are priority objectives in Eucalyptus tree improvement. The molecular basis of quantitative variation and trait expression in eucalypt hybrids, however, remains largely unknown. The recent availability of a draft genome sequence (http://www.phytozome.net) and genome-wide genotyping platforms, combined with high levels of genetic variation and high linkage disequilibrium in hybrid crosses, greatly facilitate the detection of quantitative trait loci (QTLs) as well as underlying candidate genes for growth and wood property traits. In this study, we used Diversity Arrays Technology markers to assess the genetic architecture of volume growth (diameter at breast height, DBH) and wood basic density in four-year-old progeny of an interspecific backcross pedigree of E. grandis and E. urophylla. In addition, we used Illumina RNA-Seq expression profiling in the E. urophylla backcross family to identify cis- and trans-acting polymorphisms (eQTLs) affecting transcript abundance of genes underlying QTLs for wood basic density. Results A total of five QTLs for DBH and 12 for wood basic density were identified in the two backcross families. Individual QTLs for DBH and wood basic density explained 3.1 to 12.2% of phenotypic variation. Candidate genes underlying QTLs for wood basic density on linkage groups 8 and 9 were found to share trans-acting eQTLs located on linkage groups 4 and 10, which in turn coincided with QTLs for wood basic density suggesting that these QTLs represent segregating components of an underlying transcriptional network. Conclusion This is the first demonstration of the use of next-generation expression profiling to quantify transcript abundance in a segregating tree population and identify candidate genes potentially affecting wood property variation. The QTLs identified in this study provide a resource for identifying candidate genes and developing molecular markers for marker-assisted breeding of volume growth and wood basic density. Our results suggest that integrated analysis of transcript and trait variation in eucalypt hybrids can be used to dissect the molecular basis of quantitative variation in wood property traits.

Abstract Background De novo assembly of transcript sequences produced by short-read DNA sequencing technologies offers a rapid approach to obtain expressed gene catalogs for non-model organisms. A draft genome sequence will be produced in 2010 for a Eucalyptus tree species (E. grandis) representing the most important hardwood fibre crop in the world. Genome annotation of this valuable woody plant and genetic dissection of its superior growth and productivity will be greatly facilitated by the availability of a comprehensive collection of expressed gene sequences from multiple tissues and organs. Results We present an extensive expressed gene catalog for a commercially grown E. grandis × E. urophylla hybrid clone constructed using only Illumina mRNA-Seq technology and de novo assembly. A total of 18,894 transcript-derived contigs, a large proportion of which represent full-length protein coding genes were assembled and annotated. Analysis of assembly quality, length and diversity show that this dataset represent the most comprehensive expressed gene catalog for any Eucalyptus tree. mRNA-Seq analysis furthermore allowed digital expression profiling of all of the assembled transcripts across diverse xylogenic and non-xylogenic tissues, which is invaluable for ascribing putative gene functions. Conclusions De novo assembly of Illumina mRNA-Seq reads is an efficient approach for transcriptome sequencing and profiling in Eucalyptus and other non-model organisms. The transcriptome resource (Eucspresso, http://eucspresso.bi.up.ac.za/) generated by this study will be of value for genomic analysis of woody biomass production in Eucalyptus and for comparative genomic analysis of growth and development in woody and herbaceous plants.

Scalp hair is a universal human characteristic, and a wide range of hair shape and color variations exists. Although differences in human scalp hair shape are visually apparent, the underpinning molecular insights are yet to be fully explored. This work reports the determination of differences at the protein level between two distinct groups of hair shape: very straight samples versus very curly hair samples. An in-depth highresolution liquid-chromatography mass spectrometry proteome analysis study was performed on hair samples from 50 individuals (pooled in 10 × 5 samples) with very curly hair and 50 subjects with very straight hair (pooled in 10 × 5 samples) to decipher differences between the two experimental groups at the protein level. Our results demonstrate that a distinction between the two experimental groups (very straight vs. very curly) can be made based on their overall protein profiles in a multivariate analysis approach. Further investigation of the protein expression levels between these two groups pinpointed 13 unique proteins which were found to be significantly different between the two groups, with an adjusted p-value < 0.05 and a fold change of more than two. Although differences between the very curly and the very straight hair sample groups could be identified, linkage between population differences and curl phenotype is currently unknown and requires further investigation. [ABSTRACT FROM AUTHOR]

Abstract: Introgression can introduce novel genetic variation at a faster rate than mutation alone and result in adaptive introgression when adaptive alleles are maintained in the recipient genome over time by natural selection. A previous study from our group demonstrated adaptive introgression from Populus balsamifera into P. trichocarpa in a target genomic region. Here we expand our local ancestry analysis to the whole genome of both parents to provide a comprehensive view of introgression patterns and to identify additional candidate regions for adaptive introgression genomewide. Populus trichocarpa is a large, fast‐growing tree of mild coastal regions of the Pacific Northwest, whereas P. balsamifera is a smaller stature tree of continental and boreal regions with intense winter cold. The species hybridize where they are parapatric. We detected asymmetric patterns of introgression across the whole genome of these two poplar species adapted to contrasting environments, with stronger introgression from P. balsamifera to P. trichocarpa than vice versa. Admixed P. trichocarpa individuals contained more genomic regions with unusually high levels of introgression (19 regions) and also the largest introgressed genome fragment (1.02 Mb) compared with admixed P. balsamifera (nine regions). Our analysis also revealed numerous candidate regions for adaptive introgression with strong signals of selection, notably related to disease resistance, and enriched for genes that may play crucial roles in survival and adaptation. Furthermore, we detected a potential overrepresentation of subtelomeric regions in P. balsamifera introgressed into P. trichocarpa and possible protection of sex‐determining regions from interspecific gene flow. [ABSTRACT FROM AUTHOR]

Introgression can be an important source of adaptive phenotypes, although conversely it can have deleterious effects. Evidence for adaptive introgression is accumulating but information on the genetic architecture of introgressed traits lags behind., Here we determine trait architecture in Populus trichocarpa under introgression from P. balsamifera using admixture mapping and phenotypic analyses., Our results reveal that admixture is a key driver of clinal adaptation and suggest that the northern range extension of P. trichocarpa depends, at least in part, on introgression from P. balsamifera. However, admixture with P. balsamifera can lead to potentially maladaptive early phenology, and a reduction in growth and disease resistance in P. trichocarpa. Strikingly, an introgressed chromosome 9 haplotype block from P. balsamifera restores the late phenology and high growth parental phenotype in admixed P. trichocarpa. This epistatic restorer block may be strongly advantageous in maximizing carbon assimilation and disease resistance in the southernmost populations where admixture has been detected. We also confirm a previously demonstrated case of adaptive introgression in chromosome 15 and show that introgression generates a transgressive chlorophyll-content phenotype., We provide strong support that introgression provides a reservoir of genetic variation associated with adaptive characters that allows improved survival in new environments. [ABSTRACT FROM AUTHOR]