UrdA Controls Secondary Metabolite Production and the Balance between Asexual and Sexual Development in .

The genus includes important plant pathogens, opportunistic human pathogens and mycotoxigenic fungi. In these organisms, secondary metabolism and morphogenesis are subject to a complex genetic regulation. Here we functionally characterized , a gene encoding a putative helix-loop-helix (HLH)-type regulator in the model fungus . governs asexual and sexual development in strains with a wild-type background; absence of resulted in severe morphological alterations, with a significant reduction of conidial production and an increase in cleistothecial formation, even in the presence of light, a repressor of sex. The positive effect of on conidiation is mediated by the central developmental pathway (CDP). However, overexpression was not sufficient to restore wild-type conidiation in the Δ strain. Heterologous complementation of Δ with the putative homolog also failed to rescue conidiation wild-type levels, indicating that both genes perform different functions, probably reflected by key sequence divergence. UrdA also represses sterigmatocystin (ST) toxin production in the presence of light by affecting the expression of , the activator of the ST gene cluster. Furthermore, UrdA regulates the production of several unknown secondary metabolites, revealing a broader regulatory scope. Interestingly, UrdA affects the abundance and distribution of the VeA protein in hyphae, and our genetics studies indicated that appears epistatic to regarding ST production. However, the distinct phenotype of the ΔΔ double mutant suggests that both regulators conduct independent developmental roles. Overall, these results suggest that UrdA plays a pivotal role in the coordination of development and secondary metabolism in .