DASH (Drosophila, Arabidopsis, Synechocystis, human)
cryptochromes (cry-DASHs) constitute a subgroup of the
photolyase cryptochrome family with diverse light-sensing roles, found in most taxonomical groups. The genome of Fusarium fujikuroi, a phytopathogenic fungus with a rich secondary metabolism, contains a gene encoding a putative cry-DASH, named CryD. The expression of the cryD gene is induced by light in the wild type, but not in mutants of the "white collar" gene wcoA. Targeted ΔcryD mutants show light-dependent phenotypic alterations, including changes in morphology and pigmentation, which disappear upon reintroduction of a wild-type cryD allele. In addition to microconidia, the colonies of the ΔcryD mutants produced under illumination and
nitrogen starvation large septated spores called macroconidia, absent in wild-type colonies. The ΔcryD mutants accumulated similar amounts of
carotenoids to the control strain under constant illumination, but produced much larger amounts of
bikaverin under
nitrogen starvation, indicating a repressing role for CryD in this biosynthetic pathway. Additionally, a moderate photoinduction of
gibberellin production was exhibited by the wild type but not by the ΔcryD mutants. The phenotypic alterations of the ΔcryD mutants were only noticeable in the light, as expected from the low expression of cryD in the dark, but did not correlate with
mRNA levels for structural genes of the
bikaverin or
gibberellin biosynthetic pathways, suggesting the participation of CryD in posttranscriptional regulatory mechanisms. This is the first report on the participation of a cry-DASH
protein in the regulation of fungal secondary metabolism.