Abstract
Rice grassy stunt virus (RGSV) induces excess tillering. To elucidate the molecular basis of excess tillering in rice, the gene expression changes in rice by RGSV was analysed. The bud formation is controlled by LAS, RAX, REV, Ba1. Outgrowth of the bud is controlled by auxin, SL, and CK. Our results suggested excess tillering by RGSV infection is related to simultaneous suppression of genes involved in SL and GA synthesis. To examine the relationship between symptom severity and gene responses, the gene expression of rice under infection by the three RDV strains was done. Gene silencing-related genes were activated and the degree of activation was similar among the three RDV strains. Genes for hormone-regulated defense systems were also activated, and the degree of activation seemed to be correlated with the concentration of RDV in plants. Some development and morphogenesis processes were suppressed, but the degree of suppression was not correlated well with the RDV concentration. One host mutant fails to support RDV propagation rim1-1 has been isolated and function of RIM1 gene in rice has been characterized. Here we would like to discuss its contribution to host defense system.
