Blue-light regulation of phytoene dehydrogenase (carB) gene expression in Mucor circinelloides

The carB gene, encoding the phytoene dehydrogenase of Mucor circinelloides, was isolated by heterologous hybridisation with a probe derived from the c orresponding gene of Phycomyces blakesleeanus. The cDNA and genomic copies complemented phytoene dehydrogenase defects in Escherichia coli and in carB mutants of M. circinelloides, respectively. Fluence-response curves for tr anscript accumulation were constructed after different blue-light pulses. T he level of carB mRNA accumulation reached values up to 150-fold higher tha n basal levels in darkness. Several elements In the promoter of this gene r esemble consensus sequence identified in Neurospora crassa (APE) which is e ssential for blue-light regulation. Comparison of the available phytoene de hydrogenase sequences from plants, fungi, algae and bacteria suggests that the two known types of phytoene dehydrogenase are more closely related to e ach other than previously thought.