Sequencing and analyses of the hexaploid wheat chromosome 3B

International audienceBecause of its large (17 Gb, 5x the human genome and 40x the one of rice), polyploid (3 homoeologous A-, B- and D-genomes within a same nucleus) and highly repetitive (>80% of DNA corresponding to transposable elements) genome, the development of wheat genomics has been lagging behind the one of the other major crops. Two years after the establishment of the first physical map of the biggest wheat chromosome, the 3B, which represents 1 Gb (Paux et al. Science 2008), its complete sequencing is now underway (ANR project 3BSEQ) by combining Roche 454 sequencing of pools of contiguous BACs and Whole Chromosome Shotgun sequencing by Solexa/Illumina. High throughput marker development and functional analyses based on RNASeq, tiling array and copy number variants detection are also planned in the framework of this project. In order to prepare for its complete sequencing and analysis, we performed a pilot project on 18 Mb of contiguous sequences which allowed us to improve our understanding of the wheat genome composition and evolution. Comparative and evolutionary analyses revealed a large amount of nonsyntenic genes interspersed into a conserved ancestral grass gene backbone, suggesting that the wheat gene content has been extensively rearranged probably through transposable element-mediated gene capture. Finally, bioinformatics tools and databases has been developed in order to manage automatic annotation and analyses of such a large amount of data

The grapevine genome sequence suggests ancestral hexaploidization in major angiosperm phyla.

International audienceThe analysis of the first plant genomes provided unexpected evidence for genome duplication events in species that had previously been considered as true diploids on the basis of their genetics. These polyploidization events may have had important consequences in plant evolution, in particular for species radiation and adaptation and for the modulation of functional capacities. Here we report a high-quality draft of the genome sequence of grapevine (Vitis vinifera) obtained from a highly homozygous genotype. The draft sequence of the grapevine genome is the fourth one produced so far for flowering plants, the second for a woody species and the first for a fruit crop (cultivated for both fruit and beverage). Grapevine was selected because of its important place in the cultural heritage of humanity beginning during the Neolithic period. Several large expansions of gene families with roles in aromatic features are observed. The grapevine genome has not undergone recent genome duplication, thus enabling the discovery of ancestral traits and features of the genetic organization of flowering plants. This analysis reveals the contribution of three ancestral genomes to the grapevine haploid content. This ancestral arrangement is common to many dicotyledonous plants but is absent from the genome of rice, which is a monocotyledon. Furthermore, we explain the chronology of previously described whole-genome duplication events in the evolution of flowering plants