Light-mediated participation of the VIVID-like protein of Fusarium fujikuroi VvdA in pigmentation and development.

The phytopathogen Fusarium fujikuroi is a model fungus for the production of different secondary metabolites. These include the acidic xanthophyll neurosporaxanthin, produced through the activity of the enzymes encoded by the car genes, of which carRA and carB play a major role. Expression of these genes is induced by light but, in contrast to other fungi, the induction is not impaired under continuous illumination in null mutants of the F. fujikuroi wc-1-like gene, wcoA. Therefore, we investigate the role of other blue-light photoreceptors. Here we describe the identification, regulation and targeted mutation of the F. fujikuroi gene vvdA, homologous of the Neurospora crassa vivid (vvd) gene. As found for vvd in N. crassa, expression of vvdA in F. fujikuroi is strongly stimulated by light, an activation that is severely reduced in the wcoA mutants. Deletion of vvdA in F. fujikuroi results in a paler pigmentation under constant light, explained by a reduced carotenoid production, a regulatory effect opposite to the enhanced carotenoid accumulation characteristic of the vvd mutants of N. crassa. No major changes were appreciated in the transcriptional regulation of the car genes following exposure to light, but a noticeable reduction was found upon long-term incubation under constant illumination. Additionally, the vvdA mutants produce less conidia and their colonies exhibit morphological alterations under constant light, such as a more compact development of aerial mycelia and a more solid attachment to the agar surface. The results indicate that VvdA participates in the regulation by light of mycelial development and affects the accumulation of carotenoids but it is not responsible of the transcriptional photoadaptation of the car genes.