Functional Analysis Of Rho4 And Its Putative GEF Protein Bud3 In Magnaporthe Oryzae

Magnaporthe oryzae is a causal filamentous fungus of rice blast,it has emerged as a good model organism for studying plant pathogenic fungi.Rho GTPases subfamily belongs to Ras superfamily and plays vital roles including cell morphogenesis and vesicular trafficking,by acting as master switch to cycle between an active GTP and an inactive GDP binding state.Guanine nucleotide exchange factor?GEF?has a crucial role in activating Rho GTPases by exchanging GDP for GTP.Bud3,which has a conserved GEF domain,function as a GEF of Rho4 in Saccharomyces cerevisiae.So far the functions of MoRho4?MGG₀3901?as well as its putative GEF protein MoBud3?MGG₀1695?are not clear in M.oryzae.In this study,we generated AMoBud3 by knocking out,and analysed the phenotypes of the AMoRho4,MoRho4-CA and MoRho4-DN mutants generated by the other one.Phenotypic analysis showed that deletion of MoBud3 resulted in reduced vegetative growth and conidiation with abnormal conidial morphology,the efficiency of appresorium formation was lower compared to the wild-type strain Ku80.In addition,its pathogenetic ability was compromised and septa formation was abnormal.Interestingly,the phenotypes of AMoRho4,MoRho4-CA and MoRho4-DN were similar to those of AMoBud3 in terms of vegetative growth,septal and appressorial formation and pathogenicity on rice and barley leaves.Especially,more branches were observed on the aerial hyphae of AMoRho4 and MoRho4-CA.Overall,both Rho4 and Bud3 are important regulators of vegetative growth and pathogenesis of M.oryzae.