Genetic analysis of suppressors of the veA1 mutation in Aspergillus nidulans.

Light-dependent conidiation in the filamentous ascomycete, Aspergillus nidulans, is contingent on the allelic state of the velvet (veA) gene. Light dependence is abolished by a mutation in this gene (veA1), which allows conidiation to occur in the absence of light. We have isolated and characterized six extragenic suppressors of veA1 that restore the light-dependent conidiation phenotype. Alleles of four genes, defined by complementation tests, were subjected to extensive genetic and phenotypic analysis. The results of light-dark shifting experiments and the phenotypes of double mutant combinations are consistent with the possibility that the expression of the light-dependent phenotype is regulated by specific interactions of the suppressor gene products with the velvet gene product and with each other.