Carbon source and pH-dependent transcriptional regulation of cellulase genes of Humicola grisea var. thermoidea grown on sugarcane bagasse

Time-course expression profiles of one xylanase and eight cellulase encoding genes, as well as of two transcription factor encoding genes of Humicola grisea var. thermoidea were established in different culture media pHs and carbon sources (glucose and sugarcane bagasse). Quantitative real-time RT-PCR analysis revealed a remarkable and parallel increase in mRNA accumulation for cbh1.1, cbh1.2, egl1, egl2, egl3, bgl4 and xyn1 at alkaline pH and with sugarcane bagasse employed as the sole carbon source. Glucose utilization led to a higher creA mRNA accumulation compared to the other genes. A distinct pattern was observed for egl4, whose mRNA preferably accumulated in acidic conditions. The transcriptional profile data combined with the analysis of the in vitro binding of PacC and CreA transcription factors to the promoters support the CreA-mediated carbon repression and the PacC-related pH regulation of H. grisea cellulase and xylanase encoding genes. Moreover, EMSA analyses suggest a role for CreA on pacC transcriptional regulation. These data will be useful to H. grisea hydrolytic enzymes production improvement, as well as to the design of optimized promoters aiming industrial heterologous proteins production.