Abstract:To explore the function of the LaeA protein with regard to morphological development，ochratoxin biosynthesis and oxidative stress tolerance in Aspergillus niger.Also，to contribute to a better understanding of the laeA regulatory mechanism in Aspergillus niger.We proposed the laeA gene as a potential target in developing a control strategy to prevent Aspergillus niger infection and ochratoxin biosynthesis.An Aspergillus niger laeA gene disruption strain was constructed by Agrobacterium-mediated homologous recombination.A wild type （WT）was compared with the △laeA strain to examine differences in morphological development，ochratoxin biosynthesis and oxidative stress tolerance.Compared with WT，the△laeA strain had reduced hyphal growth，hyphal branching，and conidia production.Moreover，the △laeA strain almost abolished the biosynthesis of ochratoxin A（OTA）.After 7 d of growth in both light and dark conditions，OTA production decreased by 92.45%and 99.03%，respectively，when compared with WT.The△laeA strain also showed increased sensitivity to oxidative stress.When 10 mmol/L H2O2was added to the growth medium，the△laeA strain could not grow，whereas the WT strain was able to form colonies.Compared with WT，the △laeA strain has significantly decreased antioxidant enzyme activity under 5 mmol/L H2O2oxidative stress.The LaeA protein acts as a positive regulator on conidia production，OTA biosynthesis，and oxidative stress tolerance in Aspergillus niger.