Transcriptional activator of the xylanolytic system. Involved in the regulation of extracellular cellulolytic and xylanolytic genes and in the regulation of the intracellular activities of D-xylose catabolic genes in the pentose catabolic pathway (PCP) in response to the presence of D-xylose. Binds to the DNA sequence 5'-GGNTAAA-3'. Expressed in presence of xylose. Repressed in presence of glucose through the action of the creA transcription repressor. Reduces growth on birchwod xylan, while growth is unaffected on D-xylose, xylitol and other carbon sources like D-glucose, L-arabinose or L-arabitol. Belongs to the xlnR/xlr1 family.