Blue Light Overrides Repression of Asexual Sporulation by Mating Type Genes in the BasidiomyceteCoprinus cinereus

Abstract

Monokaryotic mycelia of the homobasidiomyceteCoprinus cinereusform asexual spores (oidia) constitutively in abundant numbers. Mycelia with mutations in both mating type loci (Amut Bmuthomokaryons) also produce copious oidia but only when exposed to blue light. We used such anAmut Bmuthomokaryon to define environmental and inherent factors that influence the light-induced oidiation process. We show that theAmutfunction causes repression of oidiation in the dark and that light overrides this effect. Similarly, compatible genes from different haplotypes of theAmating type locus repress sporulation in the dark and not in the light. Compatible products of theBmating type locus reduce the outcome of light onA-mediated repression but the mutatedBfunction present in theAmut Bmuthomokaryons is not effective. In dikaryons, the coordinated regulation of asexual sporulation by compatibleAandBmating type genes results in moderate oidia production in light.