The Regulatory Mechanism of Water Activities on Aflatoxins Biosynthesis and Conidia Development, and Transcription Factor AtfB Is Involved in This Regulation.

Peanuts are frequently infected by Aspergillus strains and then contaminated by aflatoxins (AF), which brings out economic losses and health risks. AF production is affected by diverse environmental factors, especially water activity (a(w)). In this study, A. flavus was inoculated into peanuts with different a(w) (0.90, 0.95, and 0.99). Both AFB(1) yield and conidia production showed the highest level in a(w) 0.90 treatment. Transcriptional level analyses indicated that AF biosynthesis genes, especially the middle- and later-stage genes, were significantly up-regulated in a(w) 0.90 than a(w) 0.95 and 0.99. AtfB could be the pivotal regulator response to a(w) variations, and could further regulate downstream genes, especially AF biosynthesis genes. The expressions of conidia genes and relevant regulators were also more up-regulated at a(w) 0.90 than a(w) 0.95 and 0.99, suggesting that the relative lower a(w) could increase A. flavus conidia development. Furthermore, transcription factors involved in sexual development and nitrogen metabolism were also modulated by different a(w). This research partly clarified the regulatory mechanism of a(w) on AF biosynthesis and A. flavus development and it would supply some advice for AF prevention in food storage.