Genes regulated by AoXlnR, the xylanolytic and cellulolytic transcriptional regulator, in Aspergillus oryzae

摘要

XlnR is a Zn(II)_2Cys_6 transcriptional activator of xylanolytic and cellulolytic genes in Aspergillus. Overexpression of the aoxlnR gene in Aspergillus oryzae (A. oryzae xlnR gene) resulted in elevated xylanolytic and cellulolytic activities in the culture supernatant, in which nearly 40 secreted proteins were detected by two-dimensional electrophoresis. DNA microarray analysis to identify the transcriptional targets of AoXlnR led to the identification of 75 genes that showed more than fivefold increase in their expression in the AoXlnR overproducer than in the disruptant. Of these, 32 genes were predicted to encode a glycoside hydrolase, highlighting the biotechnological importance of AoXlnR in biomass degradation. The 75 genes included the genes previously identified as AoXlnR targets (xynF1, xynF3, xynG2, xylA, celA, celB, celC, and celD). Thirty-six genes were predicted to be extracellular, which was consistent with the number of proteins secreted, and 61 genes possessed putative XlnR-binding sites (5′-GGCTAA-3′, 5′-GGCTAG-3′, and 5′-GGCTGA-3′) in their promoter regions. Functional annotation of the genes revealed that AoXlnR regulated the expression of hydrolytic genes for degradation of β-1,4-xylan, arabinoxylan, cellulose, and xyloglucan and of catabolic genes for the conversion of d-xylose to xylulose-5-phosphate. In addition, genes encoding glucose-6-phosphate 1-dehydrogenase and l-arabinitol-4-dehydrogenase involved in d-glucose and l-arabinose catabolism also appeared to be targets of AoXlnR.