cigA, a light-inducible gene involved in vegetative growth in Mucor circinelloides is regulated by the carotenogenic repressor crgA

A strategy based on the differential-display technique has been applied to identify and to isolate potential target genes controlled by crgA, a negative regulator of the light-inducible carotenogenesis in the fungus Mucor circinelloides. This approach resulted in the identification and cloning of the gene cigA, whose expression is repressed by the crgA gene. After a light pulse, there is an immediate though transient accumulation of transcripts of cigA gene. A similar result was obtained when mycelia were exposed to continuous illumination, suggesting the existence of a photoadaptation mechanism in M. circinelloides. The protein sequence deduced from the nucleotide sequence of cigA shows homology to the mouse and human GDP-fucose protein Ofucosyltransferases. Null cigA mutants were generated by gene replacement. Lack of cigA function does not affect carotenogenesis but provokes a slight reduction in vegetative growth that is independent of light. Introduction of wild-type cigA alleles into a cigA(-) strain restored the wild-type phenotype for vegetative growth. These results suggest that eigA is involved in vegetative growth and, moreover, that crgA controls cellular processes other than carotenogenesis. (C) 2002 Elsevier Science (USA). All rights reserved.