RESUMO
The 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.
Assuntos
Evolução Molecular , Genoma de Planta/genética , Poliploidia , Vitis/classificação , Vitis/genética , Arabidopsis/genética , DNA Intergênico/genética , Éxons/genética , Genes de Plantas/genética , Íntrons/genética , Cariotipagem , MicroRNAs/genética , Dados de Sequência Molecular , Oryza/genética , Populus/genética , RNA de Plantas/genética , RNA de Transferência/genética , Análise de Sequência de DNARESUMO
Tetraodon nigroviridis is a freshwater puffer fish with the smallest known vertebrate genome. Here, we report a draft genome sequence with long-range linkage and substantial anchoring to the 21 Tetraodon chromosomes. Genome analysis provides a greatly improved fish gene catalogue, including identifying key genes previously thought to be absent in fish. Comparison with other vertebrates and a urochordate indicates that fish proteins have diverged markedly faster than their mammalian homologues. Comparison with the human genome suggests approximately 900 previously unannotated human genes. Analysis of the Tetraodon and human genomes shows that whole-genome duplication occurred in the teleost fish lineage, subsequent to its divergence from mammals. The analysis also makes it possible to infer the basic structure of the ancestral bony vertebrate genome, which was composed of 12 chromosomes, and to reconstruct much of the evolutionary history of ancient and recent chromosome rearrangements leading to the modern human karyotype.
Assuntos
Cromossomos/genética , Peixes/genética , Duplicação Gênica , Genoma , Vertebrados/genética , Animais , Composição de Bases , Cromossomos Humanos/genética , Sequência Conservada/genética , Evolução Molecular , Genes/genética , Humanos , Cariotipagem , Mamíferos/genética , Modelos Genéticos , Dados de Sequência Molecular , Mapeamento Físico do Cromossomo , Proteoma , Análise de Sequência de DNA , Sintenia/genética , Urocordados/genéticaRESUMO
Plant-parasitic nematodes are major agricultural pests worldwide and novel approaches to control them are sorely needed. We report the draft genome sequence of the root-knot nematode Meloidogyne incognita, a biotrophic parasite of many crops, including tomato, cotton and coffee. Most of the assembled sequence of this asexually reproducing nematode, totaling 86 Mb, exists in pairs of homologous but divergent segments. This suggests that ancient allelic regions in M. incognita are evolving toward effective haploidy, permitting new mechanisms of adaptation. The number and diversity of plant cell wall-degrading enzymes in M. incognita is unprecedented in any animal for which a genome sequence is available, and may derive from multiple horizontal gene transfers from bacterial sources. Our results provide insights into the adaptations required by metazoans to successfully parasitize immunocompetent plants, and open the way for discovering new antiparasitic strategies.
Assuntos
Genoma Helmíntico , Plantas/parasitologia , Tylenchoidea/genética , Animais , Sequência de Bases , Mapeamento Cromossômico , DNA Complementar/genética , DNA de Helmintos/genética , Etiquetas de Sequências Expressas , Genes de Helmintos , Dados de Sequência Molecular , Doenças das Plantas/parasitologia , Raízes de Plantas/parasitologia , Interferência de RNA , Alinhamento de Sequência , Análise de Sequência de DNARESUMO
Tetraodon nigroviridis is among the smallest known vertebrate genomes and as such represents an interesting model for studying genome architecture and evolution. Previous studies have shown that Tetraodon contains several types of tandem and dispersed repeats, but that their overall contribution is >10% of the genome. Using genomic library hybridization, fluorescent in situ hybridization, and whole genome shotgun and directed sequencing, we have investigated the global and local organization of repeat sequences in Tetraodon. We show that both tandem and dispersed repeat elements are compartmentalized in specific regions that correspond to the short arms of small subtelocentric chromosomes. The concentration of repeats in these heterochromatic regions is in sharp contrast to their paucity in euchromatin. In addition, we have identified a number of pseudogenes that have arisen through either duplication of genes or the retro-transcription of mRNAs. These pseudogenes are amplified to high numbers, some with more than 200 copies, and remain almost exclusively located in the same heterochromatic regions as transposable elements. The sequencing of one such heterochromatic region reveals a complex pattern of duplications and inversions, reminiscent of active and frequent rearrangements that can result in the truncation and hence inactivation of transposable elements. This tight compartmentalization of repeats and pseudogenes is absent in large vertebrate genomes such as mammals and is reminiscent of genomes that remain compact during evolution such as Drosophila and Arabidopsis.