Functional Analysis Of MgRab8, A Rab Family Member In Magnaporthe Grisea

Rab8 is a member of Rab-family proteins (also called Rab GTPase) which belong to Ras small GTPase 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 of fungal development and is involved in regulation of cell polarity growth.To know the function of Rab GTPases in Magnaporthe grisea, we started functional analysis of Rab GTPases of the fungus at whole genome level. There are 10 protein members of Rab family through the analysis of Magnaporthe grisea genome database, which have the conservative 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 gene deletion through homologous recombination. Knockout mutants of the Rab8 gene were confirmed by Southern Blot and RT-PCR. Further, we analyzed the phenotype of Mgrab8 knockout mutant. It showed that the mycelia growth reduced dramatically, as well as the conidiation decreased remarkably. The mycelia and conidia diameter have a little increase, but they still formed normal appressoira and penetrated theonion epidermics, rice leaves when it accumulates to the needed concentration. The pathogenicity of Mgrab8 mutant has a little decrease compared with the wild type strain. Moreover, we constructed the complement strain of the mutant, and rescued the phenotype defect due to the deletion of the encoding gene. Our results may suggest that MgRab8 protein participates in the protein transportation related to cell polarity growth. Therefore it leads to significant mycelia growth and conidiation reduction, and makes the pathogenicity decreased.