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Porphyra is a macrophytic red alga of the Bangiales that is important ecologically and economically. We describe the genomes of three bacteria in the phylum Planctomycetes (designated P1, P2 and P3) that were isolated from blades of Porphyra umbilicalis (P.um.1). These three Operational Taxonomic Units (OTUs) belong to distinct genera; P2 belongs to the genus Rhodopirellula, while P1 and P3 represent undescribed genera within the Planctomycetes. Comparative analyses of the P1, P2 and P3 genomes show large expansions of distinct gene families, which can be widespread throughout the Planctomycetes (e.g., protein kinases, sensors/response regulators) and may relate to specific habitat (e.g., sulfatase gene expansions in marine Planctomycetes) or phylogenetic position. Notably, there are major differences among the Planctomycetes in the numbers and sub-functional diversity of enzymes (e.g., sulfatases, glycoside hydrolases, polysaccharide lyases) that allow these bacteria to access a range of sulfated polysaccharides in macroalgal cell walls. These differences suggest that the microbes have varied capacities for feeding on fixed carbon in the cell walls of P.um.1 and other macrophytic algae, although the activities among the various bacteria might be functionally complementary in situ. Additionally, phylogenetic analyses indicate augmentation of gene functions through expansions arising from gene duplications and horizontal gene transfers; examples include genes involved in cell wall degradation (e.g., κ-carrageenase, alginate lyase, fucosidase) and stress responses (e.g., efflux pump, amino acid transporter). Finally P1 and P2 contain various genes encoding selenoproteins, many of which are enzymes that ameliorate the impact of environmental stresses that occur in the intertidal habitat. [ABSTRACT FROM AUTHOR]

Background: Plant resistance genes (R genes) exist in large families and usually contain both a nucleotide-binding site domain and a leucine-rich repeat domain, denoted NBS-LRR. The genome sequence of cassava (Manihot esculenta) is a valuable resource for analysing the genomic organization of resistance genes in this crop. Results: With searches for Pfam domains and manual curation of the cassava gene annotations, we identified 228 NBS-LRR type genes and 99 partial NBS genes. These represent almost 1% of the total predicted genes and show high sequence similarity to proteins from other plant species. Furthermore, 34 contained an N-terminal toll/interleukin (TIR)-like domain, and 128 contained an N-terminal coiled-coil (CC) domain. 63% of the 327 R genes occurred in 39 clusters on the chromosomes. These clusters are mostly homogeneous, containing NBSLRRs derived from a recent common ancestor. Conclusions: This study provides insight into the evolution of NBS-LRR genes in the cassava genome; the phylogenetic and mapping information may aid efforts to further characterize the function of these predicted R genes. [ABSTRACT FROM AUTHOR]

Cultivated citrus are selections from, or hybrids of, wild progenitor species whose identities and contributions to citrus domestication remain controversial. Here we sequence and compare citrus genomes-a high-quality reference haploid clementine genome and mandarin, pummelo, sweet-orange and sour-orange genomes-and show that cultivated types derive from two progenitor species. Although cultivated pummelos represent selections from one progenitor species, Citrus maxima, cultivated mandarins are introgressions of C. maxima into the ancestral mandarin species Citrus reticulata. The most widely cultivated citrus, sweet orange, is the offspring of previously admixed individuals, but sour orange is an F1 hybrid of pure C. maxima and C. reticulata parents, thus implying that wild mandarins were part of the early breeding germplasm. A Chinese wild 'mandarin' diverges substantially from C. reticulata, thus suggesting the possibility of other unrecognized wild citrus species. Understanding citrus phylogeny through genome analysis clarifies taxonomic relationships and facilitates sequence-directed genetic improvement. [ABSTRACT FROM AUTHOR]

Rosaceae is the most important fruit-producing clade, and its key commercially relevant genera (Fragaria, Rosa, Rubus and Prunus) show broadly diverse growth habits, fruit types and compact diploid genomes. Peach, a diploid Prunus species, is one of the best genetically characterized deciduous trees. Here we describe the high-quality genome sequence of peach obtained from a completely homozygous genotype. We obtained a complete chromosome-scale assembly using Sanger whole-genome shotgun methods. We predicted 27,852 protein-coding genes, as well as noncoding RNAs. We investigated the path of peach domestication through whole-genome resequencing of 14 Prunus accessions. The analyses suggest major genetic bottlenecks that have substantially shaped peach genome diversity. Furthermore, comparative analyses showed that peach has not undergone recent whole-genome duplication, and even though the ancestral triplicated blocks in peach are fragmentary compared to those in grape, all seven paleosets of paralogs from the putative paleoancestor are detectable. [ABSTRACT FROM AUTHOR]

Halophytes are plants that can naturally tolerate high concentrations of salt in the soil, and their tolerance to salt stress may occur through various evolutionary and molecular mechanisms. Eutrema salsugineum is a halophytic species in the Brassicaceae that can naturally tolerate multiple types of abiotic stresses that typically limit crop productivity, including extreme salinity and cold. It has been widely used as a laboratorial model for stress biology research in plants. Here, we present the reference genome sequence (241Mb) of E. salsugineum at 8x coverage sequenced using the traditional Sanger sequencing-based approach with comparison to its close relative Arabidopsis thaliana. The E. salsugineum genome contains 26,531 protein-coding genes and 51 .4% of its genome is composed of repetitive sequences that mostly reside in pericentromeric regions. Comparative analyses of the genome structures, protein-coding genes, micro RNAs, stress-related pathways, and estimated translation efficiency of proteins between E. salsugineum and A. thaliana suggest that halophyte adaptation to environmental stresses may occur via a global network adjustment of multiple regulatory mechanisms. The E. salsugineum genome provides a resource to identify naturally occurring genetic alterations contributing to the adaptation of halophytic plants to salinity and that might be bioengineered in related crop species. [ABSTRACT FROM AUTHOR]

Halophytes are plants that can naturally tolerate high concentrations of salt in the soil, and their tolerance to salt stress may occur through various evolutionary and molecular mechanisms. Eutrema salsugineum is a halophytic species in the Brassicaceae that can naturally tolerate multiple types of abiotic stresses that typically limit crop productivity, including extreme salinity and cold. It has been widely used as a laboratorial model for stress biology research in plants. Here, we present the reference genome sequence (241 Mb) of E. salsugineum at 8x coverage sequenced using the traditional Sanger sequencing-based approach with comparison to its close relative Arabidopsis thaliana. The E. salsugineum genome contains 26,531 protein-coding genes and 51.4% of its genome is composed of repetitive sequences that mostly reside in pericentromeric regions. Comparative analyses of the genome structures, protein-coding genes, microRNAs, stress-related pathways and estimated translation efficiency of proteins between E. salsugineum and A. thaliana suggest that halophyte adaptation to environmental stresses may occur via a global network adjustment of multiple regulatory mechanisms. The E. salsugineum genome provides a resource to identify naturally occurring genetic alterations contributing to the adaptation of halophytic plants to salinity and that might be bioengineered in related crop species. [ABSTRACT FROM AUTHOR]

The red seaweed Porphyra (Bangiophyceae) and related Bangiales have global economic importance. Here, we report the analysis of a comprehensive transcriptome comprising ca. 4.7 million expressed sequence tag ( EST) reads from P. umbilicalis (L.) J. Agardh and P. purpurea (Roth) C. Agardh (ca. 980 Mbp of data generated using 454 FLX pyrosequencing). These ESTs were isolated from the haploid gametophyte (blades from both species) and diploid conchocelis stage (from P. purpurea). In a bioinformatic analysis, only 20% of the contigs were found to encode proteins of known biological function. Comparative analysis of predicted protein functions in mesophilic (including Porphyra) and extremophilic red algae suggest that the former has more putative functions related to signaling, membrane transport processes, and establishment of protein complexes. These enhanced functions may reflect general mesophilic adaptations. A near-complete repertoire of genes encoding histones and ribosomal proteins was identified, with some differentially regulated between the blade and conchocelis stage in P. purpurea. This finding may reflect specific regulatory processes associated with these distinct phases of the life history. Fatty acid desaturation patterns, in combination with gene expression profiles, demonstrate differences from seed plants with respect to the transport of fatty acid/lipid among subcellular compartments and the molecular machinery of lipid assembly. We also recovered a near-complete gene repertoire for enzymes involved in the formation of sterols and carotenoids, including candidate genes for the biosynthesis of lutein. Our findings provide key insights into the evolution, development, and biology of Porphyra, an important lineage of red algae. [ABSTRACT FROM AUTHOR]

Little is known about the genetic and biochemical mechanisms that underlie red algal development, for example, why the group failed to evolve complex parenchyma and tissue differentiation. Here we examined expressed sequence tag (EST) data from two closely related species, Porphyra umbilicalis (L.) J. Agardh and P. purpurea (Roth) C. Agardh, for conserved developmental regulators known from model eukaryotes, and their expression levels in several developmental stages. Genes for most major developmental families were present, including MADS-box and homeodomain (HD) proteins, SNF2 chromatin-remodelers, and proteins involved in sRNA biogenesis. Some of these genes displayed altered expression correlating with different life history stages or cell types. Notably, two ESTs encoding HD proteins showed eightfold higher expression in the P. purpurea sporophyte (conchocelis) than in the gametophyte (blade), whereas two MADS domain-containing paralogs showed significantly different patterns of expression in the conchocelis and blade respectively. These developmental gene families do not appear to have undergone the kinds of dramatic expansions in copy number found in multicellular land plants and animals, which are important for regulating developmental processes in those groups. Analyses of small RNAs did not validate the presence of miRNAs, but homologs of Argonaute were present. In general, it appears that red algae began with a similar molecular toolkit for directing development as did other multicellular eukaryotes, but probably evolved altered roles for many key proteins, as well as novel mechanisms yet to be discovered. [ABSTRACT FROM AUTHOR]

Membrane transporters play a central role in many cellular processes that rely on the movement of ions and organic molecules between the environment and the cell, and between cellular compartments. Transporters have been well characterized in plants and green algae, but little is known about transporters or their evolutionary histories in the red algae. Here we examined 482 expressed sequence tag contigs that encode putative membrane transporters in the economically important red seaweed Porphyra (Bangiophyceae, Rhodophyta). These contigs are part of a comprehensive transcriptome dataset from Porphyra umbilicalis and Porphyra purpurea. Using phylogenomics, we identified 30 trees that support the expected monophyly of red and green algae/plants (i.e. the Plantae hypothesis) and 19 expressed sequence tag contigs that show evidence of endosymbiotic/horizontal gene transfer involving stramenopiles. The majority (77%) of analyzed contigs encode transporters with unresolved phylogenies, demonstrating the difficulty in resolving the evolutionary history of genes. We observed molecular features of many sodium-coupled transport systems in marine algae, and the potential for coregulation of Porphyra transporter genes that are associated with fatty acid biosynthesis and intracellular lipid trafficking. Although both the tissue-specific and subcellular locations of the encoded proteins require further investigation, our study provides red algal gene candidates associated with transport functions and novel insights into the biology and evolution of these transporters. [ABSTRACT FROM AUTHOR]

The starchy swollen roots of cassava provide an essential food source for nearly a billion people, as well as possibilities for bioenergy, yet improvements to nutritional content and resistance to threatening diseases are currently impeded. A 454-based whole genome shotgun sequence has been assembled, which covers 69% of the predicted genome size and 96% of protein-coding gene space, with genome finishing underway. The predicted 30,666 genes and 3,485 alternate splice forms are supported by 1.4 M expressed sequence tags (ESTs). Maps based on simple sequence repeat (SSR)-, and EST-derived single nucleotide polymorphisms (SNPs) already exist. Thanks to the genome sequence, a high-density linkage map is currently being developed from a cross between two diverse cassava cultivars: one susceptible to cassava brown streak disease; the other resistant. An efficient genotyping-by-sequencing (GBS) approach is being developed to catalog SNPs both within the mapping population and among diverse African farmer-preferred varieties of cassava. These resources will accelerate marker-assisted breeding programs, allowing improvements in disease-resistance and nutrition, and will help us understand the genetic basis for disease resistance. [ABSTRACT FROM AUTHOR]

The freshwater cnidarian Hydra was first described in 1702 and has been the object of study for 300 years. Experimental studies of Hydra between 1736 and 1744 culminated in the discovery of asexual reproduction of an animal by budding, the first description of regeneration in an animal, and successful transplantation of tissue between animals. Today, Hydra is an important model for studies of axial patterning, stem cell biology and regeneration. Here we report the genome of Hydra magnipapillata and compare it to the genomes of the anthozoan Nematostella vectensis and other animals. The Hydra genome has been shaped by bursts of transposable element expansion, horizontal gene transfer, trans-splicing, and simplification of gene structure and gene content that parallel simplification of the Hydra life cycle. We also report the sequence of the genome of a novel bacterium stably associated with H. magnipapillata. Comparisons of the Hydra genome to the genomes of other animals shed light on the evolution of epithelia, contractile tissues, developmentally regulated transcription factors, the Spemann–Mangold organizer, pluripotency genes and the neuromuscular junction. [ABSTRACT FROM AUTHOR]

Understanding how animal complexity has arisen and identifying the key genetic components of this process is a central goal of evolutionary developmental biology. The discovery of microRNAs (miRNAs) as key regulators of development has identified a new set of candidates for this role. microRNAs are small noncoding RNAs that regulate tissue-specific or temporal gene expression through base pairing with target mRNAs. The full extent of the evolutionary distribution of miRNAs is being revealed as more genomes are scrutinized. To explore the evolutionary origins of metazoan miRNAs, we searched the genomes of diverse animals occupying key phylogenetic positions for homologs of experimentally verified human, fly, and worm miRNAs. We identify 30 miRNAs conserved across bilaterians, almost double the previous estimate. We hypothesize that this larger than previously realized core set of miRNAs was already present in the ancestor of all Bilateria and likely had key roles in allowing the evolution of diverse specialist cell types, tissues, and complex morphology. In agreement with this hypothesis, we found only three, conserved miRNA families in the genome of the sea anemone Nematostella vectensis and no convincing family members in the genome of the demosponge Reniera sp. The dramatic expansion of the miRNA repertoire in bilaterians relative to sponges and cnidarians suggests that increased miRNA-mediated gene regulation accompanied the emergence of triploblastic organ-containing body plans. [ABSTRACT FROM AUTHOR]

We have used the annotations of six animal genomes (Homo sapiens, Mus musculus, Ciona intestinalis, Drosophila melanogaster, Anopheles gambiae, and Caenorhabditis elegans) together with the sequences of five unannotated Drosophila genomes to survey changes in protein sequence and gene structure over a variety of timescales—from the less than 5 million years since the divergence of D. simulans and D. melanogaster to the more than 500 million years that have elapsed since the Cambrian explosion. To do so, we have developed a new open-source software library called CGL (for "Comparative Genomics Library"). Our results demonstrate that change in intron-exon structure is gradual, clock-like, and largely independent of coding-sequence evolution. This means that genome annotations can be used in new ways to inform, corroborate, and test conclusions drawn from comparative genomics analyses that are based upon protein and nucleotide sequence similarities. [ABSTRACT FROM AUTHOR]