Abstract
There are 7 members of OsRacs family in the rice genome. We report here the function of two rice OsRac members on rice blast resistance. We determine the strength of the resistance by extension of hyphae on the inside of rice leaf sheath cells after inoculation with a GFP expressing rice blast fungus. In the Tos17 insertion mutant of OsRac5, ND7315, extension of the infected fungal hyphae was significantly decreased compared to that in Nipponbare. Introducing of OsRac5 cDNA expressed by its own promoter complemented the phenotype of the mutant. Furthermore, transgenic rice plants overexpressed a dominant negative form of OsRac5 showed enhanced blast resistance phenotype. Interestingly, overexpression of constitutively active form of OsRac3, a close paralog of OsRac5, caused a similar enhanced blast resistance phenotype. These results suggest that the loss of function of OsRac5 and the activation of OsRac3 may activate the defense responses against rice blast.
