Résumé
Rop/Rac GTPases are plant-specific signaling proteins with multiple roles among which implications in plant development and in hormone signal transduction. We present here the study of the VvRop gene family from Vitis vinifera. By examining the databases of grapevine genomic and EST sequences, using the nucleic acid and protein sequence BLAST searching software, c1ustering and assembling these sequences, we found seven full-length cDNAs encoding VvRbps. This compares to the number of Rops/Racs found in other plant species. The phylogenetic analyses indicated that VvRops could be distributed into the four groups previously described for model plants. By genetic mapping five VvRops were localised on independent linkage groups. Possible functions of VvRops were investigated through expression studies in various organs, during fruit development and in response to different suspension cell treatments. Results of VvRop expression obtained by real-time quantitative RT-PCR analyses indicated that gene expression for the seven VvRops was apparently not coordinated in the different tissues tested, but displayed rather a unique developmental expression profile during berry development. In fact, high expression levels in grape berries for ail the seven VvRops were correlated in grape berries to those stages undergoing rapid cell division and / or expansion. Whereas VvRops likely respond to distinct hormonal signaling pathways, they are howeverall involved in grape berry early development, with a higher expression level at green berry stage. No total organ specificity for VvRop expression could be evidenced, but VvRop9 displayed high expression in developping berries only. Compared to other VvRops, VvRop9 exhibited strong berry specificity, a distinct response to ABA, and characteristic sequence elements that suggest specific protein-protein interaction, as well as a distinct subcellular localization. Our results are consistent with a regulation of VvRops expression by developmental and hormonal signals.