A long noncoding RNA promotes cellulase expression in Trichoderma reesei

Trichoderma reesei is a saprotrophic fungus that is used in industry for production of carbohydrate-active enzymes such as cellulases. We discovered an intergenic region as a regulatory factor that influences the expression of these enzymes. It turned out that this region actually codes for a long non-coding RNA (HAX1). Interestingly, the length and consequently the length of HAX1 seem to have evolved during the strain selection process done for industrial purposes. We observed a HAX1-dependent phenotype in differently good enzyme producing strains. The essential transactivator of the cellulases (i.e. the Xylanase regulator 1) and HAX1 do not only share a palindromic sequence, HAX1 also bears an unusual number of binding sites for the transactivator. We wished to learn if and how those two interact and how exactly the regulation of gene expression works on the molecular level. Based on our recent findings we are able to present a model on this regulatory mechanism.