Histone acetyltransferase TGF-1 is a coactivator of blue light-responsive genes in Trichoderma atroviride

In the filamentous fungus Neurospora crassa, White Collar (WC)-1 and -2 proteins regulate all known responses to blue light. WC-1 is the photoreceptor and together with WC-2 functions as transcription factors of blue light-regulated genes. The histone acetyltransferase NGF-1 is the coactivator of blue light-responsive genes, and physically interacts with WC-1. In Trichoderma atroviride, BLR-1 and -2 are the orthologous of WC-1 and WC-2, which regulate the blue light responses in this fungus. In this work, blue light induced acetylation of histone H3 at lysines 9 and 14 (H3K9K14), paralleling the kinetics of blue light upregulated (blu) genes. Trichostatin A, a histone deacetylase inhibitor, downregulated the transcription of blu and bld-2 genes (blue light downregulated -2), and increased acetylation of H3K9K14. Deletion of tgf-1, the orthologous to ngf-1, led to a pleiotropic phenotype affecting growth, development, and blu and bld gene expression. Chromatin immunoprecipitation analysis showed that TGF-1 participates in acetylation of H3K9K14 on the promoter of phr-1, a blu gene. Furthermore, our data show that BLR-1 is necessary for acetylation of H3K9K14. Our results suggest that TGF-1 interacts with the BLR complex. Interestingly, BLR-1 and -2 interact in darkness but not after a light pulse.