Functional Analysis Of Rab Family Proteins In Magnaporthe Oryzae

Rab family proteins (also called Rab GTPases) belong to small GTPases Ras superfamily. It has been shown that Rab-GTPase plays a critical role in mediating vesicular transport between different cytoplasmic membranes, so it also plays a key role in fungal development and is involved in regulation of cell polarity growth.To characterize the function of Rab GTPases in Magnaporthe oryzae, we conducted functional analysis of Rab GTPases of the fungus at whole genome level. There are 11 putative members of Rab family in Magnaporthe grisea genome database, all of which have the conserved domains and display high homology with Rab members in other organisms. Then, we designed primers according to gene sequences of the putatitve Rab genes, and conducted Real-time PCR to obtain the expression profile during the different stages including hypha, spore, germ tube and appressorium. In order to identify the gene function, we constructed a series of gene knock-out vectors for gene deletion through homologous recombination approach. TheΔMorab51 andΔMorab7 mutants were confirmed by PCR and Real-time PCR. Further, we analyzed the phenotype ofΔMorab51 andΔMorab7 mutants. It showed that growth rate of the mycelia reduced dramatically.ΔMorab7 mutants,as well asΔMorab51 failed to cause lesions on infected rice leaves. The conidiation of theΔMorab51 mutant decreased remarkably, while theΔMorab7 mutant failed to produce conidia. The mycelia still formed normal appressoira and didn't penetrate the onion epidermics. TheΔMorab51 andΔMorab7 mutants lost pathogenicity to rice. TEM observation showed that the vacuole maturation was blocked either inΔMorab51 or inΔMorab7 mutant.Our results suggested that MoRab51 and MoRab7 participates in the transportation of proteins related to cell polarity growth and pathogenicity, which were involved in regulation of vegetative growth and conidiation in M.oryzae.