Résumé
We investigated the diversity of the Tos17 retrotransposon in the Oryza genus using a combination of Southern hybridization with a reverse transcriptase (RT) probe and an adapter-PCR mediated amplification which allowed the sequencing of the genomic regions flanking Tos17 insertions. This analysis was carried out in a collection of 96 Oryza accessions covering the diversity of the genus and 246 accessions of a core collection of O. sativa representative of the diversity of the species. Our Southern hybridization results show that Tos17 is present in all the accessions of the A-genome species, except in the South American species O. glumaepatula and in the African species O. glaberrima and O. breviligulata. Surprisingly, a hybridization signal was observed in O. officinalis, O. minuta and O. latifolia. In O. sativa, the number of putative copies of Tos17 per accession ranged from 1-11. Moreover, multivariate analysis based on presence/absence of putative copies yielded varietal clusters consistent with the isozyme classification of rice. Adapter PCR amplification and sequencing of flanking regions of Tos17 insertions in Oryza species yielded 124 good sequences which were anchored on the rice genome sequence, overall revealing 71 insertions of Tos17 in most the Oryza species, which corresponded to 36 orthologous sites. In O. sativa the same approach yielded 461 good sequences, revealing 62 positions in the 6 varietal groups, representing 28 orthologous insertion sites. Comparison of these insertions among Oryza species in one hand and between cultivated and wild Oryza species on the other hand will be presented and discussed. (Résumé d'auteur)