Functional Analysis Of Chitin Synthases In Fusarium Graminearum

Wheat Head Blight (WHB) is one of the most important devastating diseases which will cause a large loss of wheat yield and quality. So far,we have relied on chemical control to prevent its occurrence and popularity.However,the resistance of traditional agents such as carbendazim has increased dramatically,it is urgent to find a new and safe target for controlling this disease.Chitin is a major structural component of the cell wall and septum of pathogenic fungi.Chitin is transported to specific localization throughout the cell cycle to maintain the cellular stability and respond to the environmental stresses.As chitin is not represented in humans and other vertebrates,it may serve as a target for controlling the disease.Chitin is synthesized by chitin synthases (Chs).There are eight chitin synthases in Fusarium graminearum,the pathogen of wheat head blight.To determine their roles,we have constructed deletion mutants through gene deletion.And we found that deletion of FgCHS3b is lethal to F. graminearum, and the deletion mutants AFgChs 1, AFgChs2,AFgChs7 and AFgChs5 caused diverse defects in mycelial growth, conidiation, pathogenicity or response to stresses.While deletion of FgCHS3a,FgCHS4 or FgCHS6 showed no obvious difference from the wild type.Besides,we found that deletion of FgCHS2 caused thickened and "wavy"septa. Furthermore, we generated double deletion mutants of FgCHS2 and other FgCHSs and found that FgChs2 shares functions with FgChs1, FgChs7 and FgChs5 in mycelial growth, share functions with FgChs1, FgChs4, FgChs7 and FgChs5 in conidiation, shares functions in pathogenicity, DON production and septum formation with all the other six FgChss, and does not have overlapping functions in response to cell wall-damaging agents with any of the six FgChss. At last, quantitative real-time PCR (qRT-PCR) assays showed that the expression levels of FgCHSl, FgCHS3a, FgCHS4, FgCHS7, FgCHS5 and FgCHS6 in the deletion mutant AFgChs2 increased significantly, we demonstrate that other Chss complement the functions after deleting FgCHS2.Taken together, these results indicate that each chitin synthase of F. graminearum plays certain roles, although single deletion of some gene does not lead to visible change comparing with the wild type.This research will lay the foundation for studying new and safe chemical agents.