Viruses are built with a small genome coding for a limited number of proteins (5 in the RYMVs). They therefore need their host's proteins in order to accomplish each stage of their infection cycle. One of the proteins that the RYMV requires appears to be the eIF(iso)4G translation initiation factor coded by the Rymv1 gene which is probably involved in viral protein translation, but also perhaps in other processes such as the virus's movement within the cell.
The research team discovered mutations of the gene they analysed in three different resistant varieties. These are distinct but are situated in the same domain of the gene in a patch on the surface favourable for interaction with the virus. In these varieties, the mutation does not appear to alter the protein's role in its primary biological functions, but can prevent its interaction with the virus which is then blocked in one of the stages of its infectious cycle.
In parallel, a team of IRD virologists showed that it was possible to carry out laboratory selection of RYMV strains that break the gene's resistance and that the process involved was determined by mutations in one of the viral proteins. The two approaches are now being combined in order to determine the molecular mechanisms of resistance or susceptibility on the basis of direct interactions between the rice protein and that of the virus. Understanding of these mechanisms will give clues as to the best ways of making long-term use of this resistance gene.
Another strategy developed by the IRD for combating this virus involves introducing part of the viral genes into the plant genome by transgenesis, as has been done in other plant/virus interactions, with the aim of inducing resistance to RY
Source:Institut de Recherche Pour le D茅veloppement