Functional Study Of The Acetylated Protein AflO For Fungal Development And Aflatoxin Biosynthesis In Aspergillus Flavus

Aspergillus flavus is a kind of saprophytic filamentous fungus that could cause disease in both plants and animals.Its ability to contaminate many important crops and food-stuffs,which cause the production of natural toxins as well such as aflatoxin B1,B2,G1 and G2,leads to enormous agricultural economic losses and health problem in humans and animals.Previous studies demonstrated that acetylation modification of lysine residues are highly conserved and act muti-function across several organisms.However,the effect of acetylation modification of non-histone proteins on the development and pathogenicity in A.flavus is still unknown.In our previous work,we obtained some acetylated proteins in A.flavus by mass spectrometry,among which O-methyltransferase AflO was identified.In this study,we generated aflO gene deletion and complementation strains to characterize the function of aflO in the fungal development,aflatoxin biosynthesis and pathogenicity in A.flavus.The results showed that deletion strain failed to synthesize aflatoxins.The growth rate,conidiation,sclerotia formation,and the pathogenicity were found significantly decreased in AaflO mutant when compared to wild-type strain.Adding to these,we also demonstrated that the aflO deletion strains were much more sensitive to cell wall stress,oxidative and DNA damage related agents than that of wild-type strain.These results indicated that aflO was involved in the fungal development,aflatoxin biosynthesis and stress responses in A.flavus.The site mutation strains at acetylation sites of K241th and K384th(K241R,K241Q,K384R and K384Q)were further generated to investigate the role of acetylation modification of AflO in regulating the development and aflatoxin synthesis of A.flavus.The results indicated that the acetylation of K241th and K384th positions were important for aflatoxin biosynthesis.Continuous acetylation at K241th and K384th sites and deacetylation at K384th were found importantly for the growth and conidiation of A.flavus.The acetylation at K241th was also involved in sclerotia formation and colonization of A.flavus.The acetylation at K241th and K384th contributed to the adaption of environmental stresses of A.flavus.However,K241Q mutation strain displayed no significant effect on the synthesis of aflatoxin,growth,sporulation,sclerotia formation and pathogenicity.In conclusion,this work advances our understanding that acetylation modifications on Lys of K241th and K3 84th sites of O-methyltransferase AflO,not only directly participate in aflatoxin biosynthesis,but also involve in fungal growth,conidiation,sclerotia formation and pathogenicity of A.flavus,which would provide new valuable information for control strategies of this fungus.