Impact of on Ochratoxin A production, mycelium growth and pathogenicity of under water activity stress.

is a major producer of ochratoxin A (OTA), a highly toxic and carcinogenic mycotoxin found in various food and feed products. produces excessive amount of OTA under various water activity (a) conditions that occur during food and feed storage. The biosynthetic gene clusters associated with OTA production include , which plays a key role in controlling mycotoxin production in response to environmental conditions. This study explored the regulation of OTA biosynthesis in , focusing on the gene's influence under a stress. The mycelium growth of wild type and mutant strains increased by 40.7% and 50.5% under high water activity (0.96 a) respectively, at 6 days post-inoculation (dpi), indicating a stress on . While mutant did not produce OTA under both high and moderate a conditions. The wild type produced OTA and OTA biosynthetic gene expression levels were downregulated under high (0.96 a) and moderate (0.91 a) water activity. The expression level of gene in mutant was significantly lower than in the wild type. Pathogenicity tests revealed that deletion of did not significantly affect disease infection. This study shows that deleting gene greatly reduces OTA production, affecting the strain's adaptability to water activity stress.