LIGHT INDUCTION OF THE CLOCK-CONTROLLED GENE CCG-1 IS NOT TRANSDUCED THROUGH THE CIRCADIAN CLOCK IN NEUROSPORA-CRASSA

Ambient light and the circadian clock have been shown to be capable of acting either independently or in an interrelated fashion to regulate the expression of conidiation in the ascomycete fungus Neurospora cra ssa. Recently several molecular correlates of the circadian clock have been identified in the form of the morning-specific clock-controlled genes ccg-1 and ccg-2. In this paper we report studies on the regulati on of ccg-1, an abundantly expressed gene displaying complex regulatio n. Consistent with an emerging consensus for clock-controlled genes an d conidiation genes in Neurospora, we report that ccg-1 expression is induced by light, and show that this induction is independent of the d irect effects of light on the circadian clock. Although circadian regu lation of the gene is lost in strains lacking a functional clock, expr ession of ccg-1 is still not constitutive, but rather fluctuates in co ncert with changes in developmental potential seen in such strains. Li ght induction of ccg-1 requires the products of the Neurospora wc-1 an d wc-2 genes, but surprisingly the requirement for wc-2 is suppressed in conditional mutants of cot-l, a gene that encodes a cAMP-dependent protein kinase. These data provide insight into a complex regulatory w eb, involving at least circadian clock control, light control, metabol ic control, and very probably developmental regulation, that governs t he expression of ccg-1.