Résumé
Mastreviruses are single stranded DNA viruses belonging to the family Geminiviridae. These viruses are transmitted by leafhoppers mostly to monocotyledonous plants species. As for most plant viruses, research have been traditionnally focused on the fraction of the viruses that causes disease on crops despite uncultivated Poaceae plants being well established as mastreviruses hosts. Nevertheless, the demonstration of the emergence of the maize streak virus-strain A (MSV-A, the most devasting mastrevirus) through recombination between strains originating from uncultivated grasses shed lights on the importance to obtain a better understanding of the diversity and structure of virus communities at the scale of the agro-ecosystems. In our preliminary study, 144 samples of uncultivated species of Poaceae were collected from the agro-ecosystems interfaces in Reunion. A sequence-independent amplification procedure, that combined rolling circle amplification with a random amplification tagging (RCA-RA) and high-throughput sequencing (Illumina HiSeq), was then applied on full DNA extracts of plants. Several viruses reads belonging to the Mastrevirus genus were reported from twelve of the 144 samples (~8%). Beside multiple MSV variants and the maize streak Reunion virus strains, at least two species of viruses related to the Axonopus compressus streak virus and the Switchgrass mosaic streak virus were identified on multiple plant species. Cloning and Sanger sequencing procedure were carried out to obtain full viral genomes and further confirm the assignation of these isolates. Our preliminary results demonstrate that mastreviruses diversity in Reunion is larger than previsouly suspected and confirm the importance to characterize their diversity at the scale of the full agro-ecosystems. They strongly suggest that the unique mastrevirus community present in the volcanic Island of Reunion results from multiple introduction events. The study of the evolution imprints within the virus genomes will certainly be informative on the process of adaptation that operates in the evolutionary history of this viral community. (Résumé d'auteur)