| The rice blast fungus Magnaporthe oryzae,infects many important cereal crops,particularly rice.It has emerged as an important model organism for studying the growth,development and pathogenesis of filamentous fungi.Rab GTPases belonging to Ras superfamily are important molecular switches in organism.There are three Rab5-like GTPases,Ypt51,Ypt52,Ypt53 in Saccharomyces cerevisae,which play an important role in endocytic pathway and vacuolar fusion.MoYpt51 and MoYpt52 in M.oryzae are paralogs of Ypt51 and Ypt52 in S.cerevisae.To investigate the biological function of MoYpt51/52,we constructed both the dominant negative form(DN)and the constitutively active form(CA)of MoYpt51/52 and transformed into the wild-type Guy 11.After analyzing the development and pathogenesis of the MoYpt51/52-CA and DN mutants,all of mutants caused significant reduction in hyphal growth and completely blocked conidial formation.No disease symptoms were observed after using hyphal plugs of MoYpt51/MoYpt52 CA/DN mutants to inoculate normal and wounded barley and rice leaves,and intact rice roots,indicating that ectopic expression of dominant negative and constitutively active MoYpt51/52 resulted in defects in pathogenicity for M.oryzae.MoYpt51/52-CA and mutants were abnormal in vacuolar fusion and lost capabilities in sexual cross and Spitzenkorper formation.To further understand the biological function of MoYpt51/52,we generated MoYpt51/52 RNAi mutants.The results showed that the RNAi of MoYpt51 and MoYpt52 exhibited similar phenotypes as MoYpt51/52-DN in some aspects.The results suggest MoYpt51/52 plays an important role in the vegetative development and pathogenicity of Magnaporthe oryzae. |
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