Analysis of global regulation of gene expression of carbon catabolite repression during the formation of cellulases by Trichoderma reesei (Hypocrea jecorina)

The ascomycete Hypocrea jecorina (anamorph of Trichoderma reesei) is one of the most well studied cellulolytic fungi and widely used in the biotechnology industry, as in the production of second generation ethanol, pulp and paper industries, textile treatments and processing of animal feed. The carbon catabolite repression mechanism adopted by T. reesei is mediated by the transcription factor CRE1 and consists in the repression of genes related to the production of cellulase when a readily available carbon source is present in the medium. This study aims to contribute to understanding the mechanism of carbon catabolite repression during the formation of cellulases, by comparing the mutant strain of T. reesei Δcre1 with its parental, QM9414. For this, the cDNA libraries of strains QM9414 and Δcre1 grown in 1% cellulose, 1 mM sophorose and 2% glucose were sequenced by RNA-seq by LGC Genomics GmbH in Berlin/Germany, using the equipment Illumina/HiSeq2000. The results of the sequencing were analyzed by the alignment software Bowtie and DEseq package, which makes the analysis of differentially expressed genes. We obtained a total of 264 million of reads that, when analyzed, showed 815 genes differentially expressed in Δcre1 in relation to the parental QM9414 on cellulose, 2368 on sophorose and 697 on glucose, for a total of 9129 genes in the genome of T. reesei. Most of genes that were up- or down-regulated in the mutant belonged to Gene Ontology categories described as metabolic processes, membrane, oxidoreductase activity, carbohydrate metabolism and transport. Cellulolytic enzymes, genes related to the transport of substances and other transcription factors were targeted for carbon catabolite repression mediated by CRE1, in a carbon source-dependent manner. Validation of differentially expressed genes by qRT-PCR showed a high correlation between the two techniques, which can be demonstrated by a high linear coefficient of Pearson (r2 = 0.94). It is hoped that these results contribute to a better understanding of the mechanism of carbon catabolite repression in T. reesei, enhancing the application of this fungus in several biotechnology sectors in which is used. (AU)