A gene of the opsin family in the carotenoid gene cluster of Fusarium fujikuroi.

Opsins are membrane photoreceptors closely related to the heat-shock proteins of the HSP30 family. Their functions include light-driven ion pumping in archaea and light detection in algae and animals, using the apocarotenoid retinal as a light-absorbing prosthetic group. We describe a gene of Fusarium fujikuroi, carO, coding for a polypeptide resembling opsins and HSP30-like proteins and contiguous to the genes of the carotenoid pathway, carRA and carB. Transcription of carO is induced by light and is deregulated in carotenoid-overproducing mutants. The same regulation pattern is exhibited by carRA and carB; and common conserved DNA elements are found in the three promoters. Heat shock resulted in a modest induction of carO transcription, similar to the one exhibited by carB, confirming a common regulation. Targeted mutagenesis of carO produced no apparent phenotypic modification, including no change in the photoinduction of carotenoid biosynthesis.