Rapid blue light regulation of a Trichoderma harzianum photolyase gene

Photolyases and blue light receptors belong to a superfamily of flavoprotei ns that make use of blue and UVA light either to catalyze DNA repair or to control development. We have isolated a DNA photolyase gene (phr1) from Tri choderma harzianum, a common soil fungus that is of interest as a biocontro l agent against soil-borne plant pathogens and as a model for the study of light-dependent development. The sequence of phr1 is similar to other Class I Type I eukaryotic photolyase genes. Low fluences of blue light rapidly i nduced phr1 expression both in vegetative mycelia, which lack photoprotecti ve pigments, and, to a greater extent, in conidiophores. Thus, visible ligh t induces the development of pigmented, resistant spores as well as the exp ression of phr1, perhaps announcing in this way the imminent exposure to th e more damaging short wavelengths of sunlight. Light induction of phr1 in n onsporulating mutants shows that a complete sporulation pathway is not requ ired for photoregulation. The light requirements for photoinduction of phr1 were not altered in dimY photoperception mutants. This suggests that photo induction of sporulation and of photolyase expression is distinct in their photoreceptor system or in the transduction of the blue light signal.