Molecular characterization of upstream regulatory sequences controlling the photoinduced expression of the albino-3 gene of Neurospora crassa.

In the filamentous fungus Neurospora crassa the biosynthesis of carotenoids is regulated by blue light, principally through transcriptional activation of some key genes in the carotenogenic enzymatic pathway. Here we report the characterization of the photoinducible promoter of the albino-3 (al-3) gene, encoding GGPP synthase. We have modified the 5' non-coding sequence of the cloned al-3 gene by deletion and site-directed mutagenesis, and we have tested the residual photoinducibility of the different constructs by transformation and subsequent analysis of gene expression in dark-grown and light-induced mycelia. The results indicate that a promoter region between positions -226 and -55 contains all the necessary information for blue light photoinduction. Multiple regulatory elements are involved in the regulated expression of the al-3 gene. One (termed the APE element) is important for the light-induction switch on of the gene and a second belongs to the CCAAT boxes family. The putative APE element is also found in the promoter of other N. crassa photoinducible genes.