RcoA has pleiotropic effects on Aspergillus nidulans cellular development

Aspergillus nidulans rcoA encodes a member of the WD repeat family of prote ins. The RcoA protein shares sequence similarity with other members of this protein family, including the Saccharomyces cerevisiae Tup1p and Neurospor a crassa RCO1. Tup1p is involved in negative regulation of an array of func tions including carbon catabolite repression. RCO1 functions in regulating pleiotropic developmental processes, but not carbon catabolite repression. In A. nidulans, deletion of rcoA (Delta rcoA), a recessive mutation, result ed in gross defects in vegetative growth, asexual spore production and ster igmatocystin (ST) biosynthesis. Expression of the asexual and ST pathway-sp ecific regulatory genes, brlA and aflR, respectively, but not the signal tr ansduction genes (i.e. flbA, fluG or fadA) regulating brlA and aflR express ion was delayed (brlA) or eliminated (aflR) in a Delta rcoA strain. Overexp ression of aflR in a Delta rcoA strain could not rescue normal expression o f downstream targets of AflR. CreA-dependent carbon catabolite repression o f starch and ethanol utilization was only weakly affected in a Delta rcoA s train. The strong role of RcoA in development, vegetative growth and ST pro duction, compared with a relatively weak role in carbon catabolite repressi on, is similar to the role of RCO1 in N. crassa.