Study On The Function Of Transcription Factors AflAtfA And AflAtfB In Aspergillus Flavus

Aspergillus flavus is a common saprophytic fungus that widely exists in nature.This fungus can produce one of the most toxic and carcinogenic secondary metabolite,aflatoxin.In addition,A.flavus and aflatoxin contaminate grains,food and feeds,causing huge economic losses and food safety issues.The growth and development,the stress response and the aflatoxin biosynthesis are regulated by regulatory factors in A.flavus.However,a large number of regulatory mechanisms in A.flavus are still unclear.In this study,the functions of the bZIP transcription factor genes AflatfA and AflatfB in A.flavus were analyzed by bioinformatics,molecular biology and fungal biology.The main results were as follows:1.The characteristics of the bZIP transcription factors AflAtfA and AflAtfB of A.flavus and the evolutionary analysis of AflAtfA.The bZIP transcription factor AflAtfA protein was predicted to encode a 512 amino acids protein,including four domains:basic leucine zipper,osmotic stress,active meiotic recombination,and repress meiotic recombination,while AflatfB gene encodes a 318 amino acids protein,only containing a basic leucine zipper domain.AflAtfA is more closely related to the evolution of otherAtfA protein in Aspergillus.AflatfB gene is regulating the transcription of AflatfA gene.2.AflAtfA and AflAtfB are involved in mycelium growth and sclerotia formation.Both AflAtfA and AflAtfB play positively role in the regulation of the vegetative growth in A.flavus,while the regulation of AflatfB gene depended on the type of medium.AflAtfA negatively regulated the sclerotia production,however,AflAtfB positively regulated the production of sclerotia.And the effect of AflAtfA on growth and sclerotia production was stronger.3.The stress response of A.flavus is regulated by two transcription factors,AflAtfA and AflAtfB.Compared with the wild type(WT),the sensitivity to H₂O₂was lower,the germination rate of spores decreased,and the inhibition rate of mycelial growth were decreased in?AflatfA,?AflatfB and?AflatfA?AflatfB strains.?AflatfA and?AflatfA?AflatfB mutants were more resistant to 1.0 M Na Cl and 1.4 M sorbitol than WT,but less sensitive to 1.5 M Na Cl and 1.8 M KCl.In addition,the viability of spores in?AflatfA and?AflatfA?AflatfB was lower than that of WT when treated with 4?and 50?.Therefore,AflAtfA and AflAtfB participated in the response to reactive oxygen,while AflatfA gene was involved in osmotic stress response and temperature stress response.4.The transcription factors AflAtfA and AflAtfB play positive roles in the regulation of aflatoxin production in A.flavus.The aflatoxin production of?AflatfA,?AflatfB and?AflatfA?AflatfB was significantly lower than that of WT strains in YES medium and infected seeds.The number of conidia on infected seeds was significant reduced in?AflatfA and?AflatfA?AflatfB mutants.Therefore,AflAtfA was crucial for aflatoxin production and spore production in A.flavus,while AflAtfB only regulated the production of aflatoxin.These results will not only provide a theoretical basis for revealing the regulatory mechanism of the growth and development,stress response and aflatoxin production,but also help to generate effective control strategies for the earlier prevention and control of A.flavus and aflatoxin hazards.