Carbon catabolite repression gene creA regulates morphology, aflatoxin biosynthesis and virulence in Aspergillus flavus

Carbon catabolite repression (CCR) is a very important mechanism employed in the utilization of carbon as an energy source, required for the regulation of growth, development and secondary metabolite production in fungi. Despite the wide study of this mechanism in fungi, little is known about the major CCR gene creA in A. fiavus. Hence, we report identification of A. fiavus carbon catabolite repression gene creA, which is responsible for the repression of secondary carbon sources. Gene deletion and over-expression was employed to explicate the role of creA in the morphology, pathogenicity, and secondary metabolite production in A. flavus. We investigated these factors using three carbon sources including glucose, sucrose and maltose. Gene deletion mutant (Delta creA) had a significant growth defect on complete medium and minimal medium containing maltose. Conidia production in Delta creA was significantly impaired irrespective of the carbon source available, while sclerotia production was significantly increased, compared to wild type (WT) and over-expression strain (OE::creA). Importantly, Delta creA produced insignificant amount of aflatoxin in complete medium, and its ability to colonize hosts was also impaired. Concisely, we showed that creA played an important role in the morphology, pathogenicity and secondary metabolite production of A. fiavus.