The inhibitory mechanism of methyl jasmonate on Aspergillus flavus growth and aflatoxin biosynthesis and two novel transcription factors are involved in this action

As the most toxic and carcinogenic mycotoxin, aflatoxin B1 (AFB1) biosynthesis depends on a series of enzymatic reactions and a complicated regulatory system. Methyl jasmonate (MeJA) is one of stress associated phytohormones. In this study, MeJA could inhibit A. flavus growth and AFB1 production with a dose-dependent manner. SEM and TEM analysis indicated that morphological ultrastructure deteriorations were observed in A. flavus treated with MeJA. RNA-Seq indicated that the initial-steps aflatoxins (AFs) genes were no drastic difference, but the middle- and later- steps genes were significantly down-regulated, which might be due to the decreases of global regulators, especially AtfB. More importantly, two novel regulators (AFLA_085880 and AFLA_015850) were involved in the inhibition, and were recognized as the critically positive regulators for AFs productions. The two genes mutants also showed significantly decrease expressions of AFs cluster genes and AFs associated regulators, and subsequent AFB1 biosynthesis. This research partly clarified inhibitory mechanism of MeJA and made some contributions to the elimination of AFs contamination.