The Trichoderma reesei xylanase2 transcriptosome: Regulation and modifaction of the key factors

Most species of Trichoderma, a filamentous ascomycete, are saprophytes. They degrade a wide variety of bio- polymeric substrates such as cellulose and hemicelluloses, predominant components of plant material and therefore renewable resources. Studies on gene regulation of expression of hydrolases aid in the improvement of enzyme production both by nutritional strategies and bioprocess design and also support effort towards recombinant overproduction of these hydrolases or of heterologous proteins under the control of their promoters. As the insertion of multiple copies of various hydrolytic genes into Trichoderma did not substantially alter/improve the amounts of enzymes produced, the identification of in cis acting elements and in trans acting factors involved in the expression of these genes help to overcome potential bottlenecks in enzyme production. Understanding of different regulatory mechanisms serve as basis to develop strains expressing tailor made enzyme cocktails needed in several industrial applications or lead to the design of artificial promoters with defined switching mechanisms to be used in heterologous protein production. In research on regulation of production of hemicellulolytic enzymes in fungi, Trichoderma, has - together with Aspergillus - the leading role. Significant progress has been made during the last few years in the identification and characterisation of cis-acting elements and trans-acting factors regulating xylanase expression. Interestingly, all of the factors known to date conferring activation of transcription on the basal and/or induced level bind their target sites irrespective of growth conditions. This observation plays the "regulatory ball" back to repressing factors and/or induction-specific amendment of the activating factors either by interacting proteins or by covalent modification (e.g. phosphorylation). To this end the model system of regulation of xylanase 2 expression in Trichoderma reesei will be used in this study to isolate and characterise such a specific repressor and to investigate the covalent modification of an inducing factor rendering it into its active form.

Most species of Trichoderma, a filamentous ascomycete, are saprophytes. They degrade a wide variety of bio- polymeric substrates such as cellulose and hemicelluloses, predominant components of plant material and therefore renewable resources. Studies on gene regulation of expression of hydrolases aid in the improvement of enzyme production both by nutritional strategies and bioprocess design and also support effort towards recombinant overproduction of these hydrolases or of heterologous proteins under the control of their promoters. As the insertion of multiple copies of various hydrolytic genes into Trichoderma did not substantially alter/improve the amounts of enzymes produced, the identification of in cis acting elements and in trans acting factors involved in the expression of these genes help to overcome potential bottlenecks in enzyme production. Understanding of different regulatory mechanisms serve as basis to develop strains expressing tailor made enzyme cocktails needed in several industrial applications or lead to the design of artificial promoters with defined switching mechanisms to be used in heterologous protein production. In research on regulation of production of hemicellulolytic enzymes in fungi, Trichoderma, has - together with Aspergillus - the leading role. Significant progress has been made during the last few years in the identification and characterisation of cis-acting elements and trans-acting factors regulating xylanase expression. Interestingly, all of the factors known to date conferring activation of transcription on the basal and/or induced level bind their target sites irrespective of growth conditions. This observation plays the "regulatory ball" back to repressing factors and/or induction-specific amendment of the activating factors either by interacting proteins or by covalent modification (e.g. phosphorylation). To this end the model system of regulation of xylanase 2 expression in Trichoderma reesei will be used in this study to isolate and characterise such a specific repressor and to investigate the covalent modification of an inducing factor rendering it into its active form.