The Functional Analysis Of VeA And LaeA In Aspergillus Niger

Aspergillus niger,as an important industrial fermentation microorganism,is widely used in food and enzyme preparation,but its toxin production is a threat to human health.This paper studied the effects of global regulatory factors veA and lae A in A.niger on Ochratoxin A(OTA)biosynthesis,fungal growth and stress response under oxidative stress regulation function,which might provide theoretical reference basis for effectively control the growth of A.niger and toxin-producing and further exploration of the A.niger in network control.(1)AveA and ?laeA strains were selected in this study based on screening experiment with the method of agrobacterium infection.Hygromycin gene was precisely inserted in ?veA and ?laeA strains,which was determined through resequencing.The insert way is reverse insert and the gene copy number is 1.The genetic stability of the strain was verified by gene stability analysis.(2)Compared with A.niger A14 phenotypic,we found that spore production and colony growth diameter of ?veA and AlaeA strains were decreased at different levels,the hyphae were longer and looser and the colony diameter was relatively smaller.There was no obvious difference in the phenotype of spore.(3)In this study,no OTA was detected in AveA strains during the growth of 7 days using HPLC-FLD,compared with A.niger A14,the defect of veA gene caused low expression levels of pks which was essential in OTA biosynthesis.In addition,OTA biosynthesis of ?laeA strains was also significantly reduced,particularly in the 7th d,the biosynthesis of OTA decreased by 92.45%in the light and 99.03%in the dark.(4)The dynamics analysis OTA,OT? and OTa in A.niger A14 revealed that OTA,OT? and OTa were increasing in the growth of 3-9 d,and OTA and OT? were more increased slowly than OT?;In addition,under the condition of dark,the relative amounts OTa and OTA was obviously higher than that of light conditions,the relative amount of OTa at the 9th d was 1.48 times than that of light conditions,the relative amount of OTA at the 9th d was 1.81 times than that of light conditions.(5)The results of oxidative stress tests showed that toxin synthesis and activity of antioxidant enzymes were increased in A.niger A14 to balance the intracellular excess reactive oxygen species.AveA and AlaeA strains were increased the sensitive to H2O2 and were completely inhibited under the stress condition of 10 mM H2O2.In response to oxidative stress,AveA and AlaeA mutant strains reduced the regulation of oxidase.