The regulation of BbLaeA on the production of beauvericin and bassiatin in Beauveria bassiana.

Beauvericin and bassiatin are two valuable compounds with various bioactivities biosynthesized by the supposedly same nonribosomal peptide synthetase BbBEAS in entomopathogenic fungus Beauveria bassiana. To evaluate the regulatory effect of global regulator LaeA on their production, we constructed BbLaeA gene deletion and overexpression mutants, respectively. Deletion of BbLaeA resulted in a decrease of the beauvericin titer, while overexpression of BbLaeA increased its production by 1-2.26 times. No bassiatin could be detected in ΔBbLaeA and wild type strain of B. bassiana, but 4.26-5.10 µg/mL bassiatin was produced in OE::BbLaeA. Furthermore, additional metabolites with increased production in OE::BbLaeA were isolated and identified as primary metabolites. Among them, 4-hydroxyphenylacetic acid showed antibacterial bioactivity against Ralstonia solanacearum. These results indicated that BbLaeA positively regulates the production of beauvericin, bassiatin and various bioactive primary metabolites.