The Response Regulator AflSkn7 Contributes To Morphological Development,Stress Response,and Pathogenicity In The Fungus Aspergillus Flavus

Aspergillus flavus is a saprophytic soil fungus that infects and contaminates preharvest and postharvest seed crops.The fungus is also an opportunistic animal and human pathogen causing aspergillosis diseases.Aflatoxins,with strong toxicity and carcinogenicity,are secondary metabolites produced by A.flavus and A.parasiticus.The aflatoxin biosynthesis is regulated by the gene cluster,which contains thirty genes.Besides,some transcription factors,such as AP-1 and also directly or indirectly involves in the regulation of aflatoxin biosynthesis.Response regulator Skn7(Suppressor of kre nine 7)is a stress-responsive transcription factor.Skn7 protein has a DNA binding domain similar to that of the heat shock transcription factor(HSF)at the N-terminal and a receiver domain at the C-terminal.In this study,skn7 deletion mutants(?AflSkn7)in A.flavus were constructed and series of phenotype on the mutans were observed.It was observed that AflSkn7 played an important role in mycelium growth,conidial formation,sclerotia generation,cell wall integrity,oxidative stress response,aflatoxin synthesis and seeds infection.As the results shown,?AflSkn7 had a slightly faster growth rate and a fewer spores production compared to the WT.AflSkn7 can affect the sclerotia generation by regulating the expression levels of AflnsdC and AflnsdD.AflSkn7 had an increased sensitivity to cell wall damaging agents CFW and CR.AflSkn7 can affect A.flavus in response to oxidative stress by regulating the expression levels of genes associated with oxidative stress.AflSkn7 can affect aflatoxin biosynthesis by regulating the expression levels of genes involved in the aflatoxin formation.In comparison to the WT,?AflSkn7 had a slow growth rate,a decreased conidial formation,and a reduced aflatoxin production when colonized on maize.Otherwise,we also found that AflSkn7 did not respond to osmolarity stress.In summary,PflSkn7 plays an important role in the regulation of morphological development,stress response,and pathogenicity in the fungus A.flavus.This study opened a new way to development of controling A.flavus means in future.