Trichoderma atroviride PHR1, a fungal photolyase responsible for DNA repair, autoregulates its own photoinduction.
The photolyases, DNA repair enzymes that use visible and long-wavelength UV light to repair cyclobutane pyrimidine dimers (CPDs) created by short-wavelength UV, belong to the larger photolyase-cryptochrome gene family. Cryptochromes (UVA-blue light photoreceptors) lack repair activity, and sensory and regulatory roles have been defined for them in plants and animals. Evolutionary considerations indicate that cryptochromes diverged from CPD photolyases before the emergence of eukaryotes. In prokaryotes and lower eukaryotes, some photolyases might have photosensory functions. phr1 codes for a class I CPD photolyase in Trichoderma atroviride. phr1 is rapidly induced by blue and UVA light, and its photoinduction requires functional blue light regulator (BLR) proteins, which are White Collar homologs in Trichoderma. Here we show that deletion of phr1 abolished photoreactivation of UVC (200 to 280 nm)-inhibited spores and thus that PHR1 is the main component of the photorepair system. The 2-kb 5' upstream region of phr1, with putative light-regulated elements, confers blue light regulation on a reporter gene. To assess phr1 photosensory function, fluence response curves of this light-regulated promoter were tested in null mutant (Deltaphr1) strains. Photoinduction of the phr1 promoter in Deltaphr1 strains was >5-fold more sensitive to light than that in the wild type, whereas in PHR1-overexpressing lines the sensitivity to light increased about 2-fold. Our data suggest that PHR1 may regulate its expression in a light-dependent manner, perhaps through negative modulation of the BLR proteins. This is the first evidence for a regulatory role of photolyase, a role usually attributed to cryptochromes.
Berrocal-Tito
Gloria M
GM
Laboratorio Nacional de Genómica para la Biodiversidad, Cinvestav Campus Guanajuato, Km 9.6 Libramiento Norte Carretera Irapuato-León, A.P. 629, Irapuato 36500, Guanajuato, México.
Esquivel-Naranjo
Edgardo U
EU
Horwitz
Benjamin A
BA
Herrera-Estrella
Alfredo
A
D000595:Amino Acid Sequence; D056931:Cryptochromes; D004260:DNA Repair; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics* / Q000502:physiology; D005420:Flavoproteins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology; D017353:Gene Deletion; D015870:Gene Expression / Q000528:radiation effects; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006706:Homeostasis; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000528:radiation effects; D014242:Trichoderma / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D014466:Ultraviolet Rays
D056931:Cryptochromes; D005420:Flavoproteins; D005656:Fungal Proteins; D049452:Green Fluorescent Proteins; D004255:Deoxyribodipyrimidine Photo-Lyase