All v.70 v.71 v.72 v.73 v.74 Photochemistry and Photobiology, Vol. Abstract Blue light and development regulate the expression of the phr1 gene of the filamentous fungus Trichoderma harzianum. The predicted product of phr1, the DNA repair enzyme photolyase, is likely to help protect Trichoderma, which grows in the soil as a mycoparasite or saprophyte, from damage upon emergence and exposure to ultraviolet-c. As no other genes displaying rapid, direct light regulation have been described previously in this organism, we have characterized the fluence and time dependence of phr1 induction, and its relation to sporulation and photoreactivation.
Induction is transient following a pulse, and, with slower decay, in continuous light.
This implies that the photoreceptor, transducers or response are capable of adaptation. About two-fold more light is required to induce phr1 than conidiation, but this difference is modest, so both responses could use the same or similar chromophore. Light regulation of phr1, however, is indifferent to both these effectors. Induction of photolyase expression behaves as a direct, rapid response to light, independent of the induction of sporulation. Indeed, illumination of mature spores increases their capacity for photoreactivation.