Identification of elevated transcripts in a Trichoderma reesei strain expressing a chimeric transcription activator using suppression subtractive hybridization

To know how the two transcription repressors Cre1 and ACEI affect their downstream genes, a new strategy was employed in which a plasmid encoding a chimeric transcription activator containing the DNA binding domains from Cre1 and ACEI and the effector domain from ACEII was constructed and transformed into Trichoderma reesei. Nineteen elevated transcripts were identified in the transformant against its parent strain using suppression subtractive hybridization. All of them had the consensus binding motif for Cre1 (5'-SYGGRG-3') and ACEI (5'-AGGCA-3'), among which seven had the most representative binding motif (5'-AGGCAAA-3') for ACEI in their 1,000-bp promoters. Cre1 could bind to the promoters of all the genes while ACEI could bind to the promoters of six out of the seven in vitro. The results provide a primary overview of a set of genes which may be associated to Cre1 or ACEI. It is the first step towards an understanding of the regulatory roles of the two repressors in cellular pathways, which would be helpful in strain improvement in T. reesei.