Effects of light on secondary metabolism and fungal development of Fusarium graminearum

Abstract

The objectives of this study were (i) to characterize white-collar (WC) orthologues of the filamentous fungus Fusarium graminearum, (ii) to investigate light-responsive phenotypes by the deletion of Fgwc-1 and Fgwc-2 genes and (iii) to examine the roles of those genes in constant light and darkness in relation to secondary metabolite synthesis and development. Production of secondary metabolites and asexual/sexual development of deletion mutants, ΔFgwc-1 and ΔFgwc-2, were assessed in constant light and darkness compared to the wild-type strain. The results showed that deletion of Fgwc-1 and Fgwc-2 impaired early onset of carotenogenesis, photoreactivation and the maturity of perithecia during sexual development. Conidiation of the ΔFgwc-1 and ΔFgwc-2 mutants was derepressed in constant light, but not in darkness. Moreover, the individual mutants produced more aurofusarin and trichothecenes than the wild-type strain in both constant light and darkness. Both Fgwc-1 and Fgwc-2 are required for light-dependent processes in F.graminearum, whereas light-independent processes such as aurofusarin and trichothecene biosynthesis are derepressed by deletion of these genes. Thus, Fgwc-1 and Fgwc-2 play roles as positive and negative regulators, depending on the requirement of light for biological activity. These results will extend the knowledge of the photobiology of Fusarium graminearum and will increase current understanding of light regulatory mechanisms mediated by white collar in secondary metabolism and fungal development.