Tissue-specific repression of starvation and stress responses of the Neurospora crassa con-10 gene is mediated by RCO1

The Neurospora crassa con-10 gene is weakly expressed in mycelia but is induced approximately 1000-fold during macroconidiation. Studies of the promoter elements and trans-acting factors that regulate con-10 expression are needed to gain a detailed understanding of developmental regulation. The rco-1 mutant displays a 10-fold elevated basal level of expression of con-10. In contrast to the wild type, con-10 expression in mycelia of the rco-1 mutant was rapidly induced to high levels by starvation for carbon or nitrogen and by heat shock. Although con-10 is developmentally induced late in conidiation, con-10 was inducible by heat shock shortly after exposure of the wild-type mycelium to air. These findings support the view that RCO1 is a cell type-specific repressor of con-10. We propose that inactivation of RCO1 allows developing conidiophores to adjust the timing of con-10 induction in response to stress.