Influence of Ace2 on the expression of the xylanolytic activity of Trichoderma reesei on different carbon sources

The xylanase system of the filamentous fungus Trichoderma reesei consists of two specific xylanases, Xyn1 and Xyn2, which are simultaneously expressed during growth on xylan but respond differentially to low molecular weight inducers. We have recently demonstrated that a deletion within the xylanase-activating element in the xyn2 promoter (XAE) completely eliminated binding of the cellulase and xylanase regulator Ace2 and there-by fully abolished transcription of xyn2 under both conditions. In the presented study we made use of an Ace2 deletion strain to elucidate the influence of this factor on the transcriptional regulation of xynl and xyn2 gene expression. The parental strain T. reesei QM 9414 and the deletion strain were cultivated under non inducing (glucose) and inducing (xylan, cellulose) conditions. Thereafter the corresponding enzyme activities were detected and respective mRNA levels were quantified via Real Time PCR. In contrast to the results obtained from the deletions in XAE of xyn2 the affects of the Ace2 deletion are less pronounced. These findings give strong indications for an additional factor contacting XAE thereby mediating expression of xyn2. The pattern of mRNA formation of xynl does not show significant changes comparing these two strains.