Functional Analysis Of A Sec2 Homolog In Magnaporthe Oryzae

Filamentous ascomycete fungus Magnaporthe oryzae is the causal agent of the rice blast disease,and is the model organism for studying fungal phytopathogens.Rab GTPase subfamily belongs to Ras superfamily and plays vital roles in vesicular trafficking by acting as a molecular switch cycling between the active GTP-bound form and the inactive GDP-bound form.Guanine nucleotide exchange factor?GEF?has a crucial role in activating Rab GTPases by exchanging GDP for GTP.Our previous study showed that Rab GTPase MoSec4 is critical for the growth,development and pathogenicity of M oryzae,but the regulatory mechanism of its activity was still not clear.In Saccharomyces cerevisiae,Sec2,containing a conserved GEF domain,has been proved to be a GEF of Sec4,thus,in this study,we identified the Sec2 homolog MGG₀2923 in M.oryzae,and named it MoSec2.Through target gene deletion and related phenotypic analysis,we found that,compared with the wild type strain 70-15,the vegetative growth rate,conidiation,and virulence of ?Mosec2 mutants were all decreased Interestingly,the above phenotypic defects,to some extent,were similar to those in ?Mosec4 mutants,indicating that MoSec2 might act as a GEF for MoSec4 and regulate the growth,conidiation,and virulence of M.oryzae through regulating the activity of MoSec4.Our results established the foundation for further illuminating the function mechanism of MoSec4.