Phenotypic analyses of ΔwcoA and ΔwcoB mutants in Fusarium fujikuroi reveal dark and light-dependent functions as a white-collar complex

The Fusarium fujikuroi fungus, known as a biotechnological source of gibberellins, has a complex secondary metabolism that responds to various environmental signals, including the availability of light and nitrogen. White collar complex proteins, consisting of the flavoprotein WC1 and its partner WC2, are widespread in fungi where they play a central role in the regulation of numerous genes in response to light. Fusarium fungi possess one copy of each WC gene, named wcoA and wcoB in F. fujikuroi. Function of WcoA was previously investigated for the phenotypic effects of its mutation and the consequences on the transcriptome. In this work we have obtained deletion mutants of the wcoA and wcoB genes in IMI58289 genetic background and the expression of some light-regulated genes related to photobiology, development, and stress, as well as genes for key enzymes of secondary metabolism have been analyzed. The results show that several investigated genes require both WcoA and WcoB to be induced by light, and in some cases, also to be correctly expressed in darkness. The regulatory alterations observed in the wcoA or wcoB mutants are mostly coincidental, indicating the functioning of the encoded proteins as a complex. On the other hand, the diversity of effects on different genes of secondary metabolism, as well as the differences of these effects with those previously observed in another wild-type strain, indicate a high functional versatility of the predicted white-collar complex in the genus Fusarium.