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Functional analysis of the transcription factor XINR involved in regulation of transcription of cellulases - and hemicellulases-enconding genes in Aspergillus niger

Abstract

The high cost of hydrolyzing biomass polysaccharides to fermentable sugars remains a major obstacle to be overcome before cellulosic ethanol can effectively be commercialized. The costs of cellulases and hemicellulases contribute substantially to the price of bioethanol. New studies to understand and improve cellulase efficiency and productivity are of paramount importance. Filamentous fungi like Aspergillus niger and Trichoderma reesei are impressive producers of hydrolytic enzymes already applied in a series of industrial processes, e.g. food, feed, pulp, paper, and textile industries. The A. niger xlnR transcription factor is a master regulator that activates enzymes of the xylanolytic system, a number of endocellulases and two cellobiohydrolases. The study of transcriptional regulators involved in the activation of genes that encode enzymes responsible for the degradation of cellulose and hemicelluloses could provide several advantages for further genetical improvement of biomass-degrading microorganisms. A potential strategy to modify expression patterns of cellulose and/or hemicellulase could follow either a constitutive or induced expression of modified versions of the regulatory proteins. The design of constitutively activated or even structuraly modified transcription factors may lead to strains allowing inducer substance-independent enzyme production. Our project aims to provide basic information about the fine regulation at transcriptional level of A. niger genes that encode hydrolytic enzymes under the control of the transcription factor XlnR. Furthermore, we also plan to identify protein partners of XlnR that could be involved either in its down-regulation, for example via carbon repression, or additional proteins that help in the assembly of the transcription machinery aiming the establishment of the gene expression regulated by XlnR. (AU)