ManR, a novel Zn(II)2Cys6 transcriptional activator, controls the β-mannan utilization system in Aspergillus oryzae

Fungal endo-beta-mannanases (beta-mannanases) are widely used as industrial enzymes: however, no transcriptional regulator of beta-mannanases has been identified in fungi or other eukaryotic cells to date. To identify a transcriptional regulator of beta-mannanases in Aspergillus oryzae, a gene-disruptant library of transcriptional regulators was screened for mutants exhibiting reduced beta-mannanase activity by using konjac glucomannan as the substrate, and ManR, a Zn(II)(2)Cys(6) type DNA binding protein was identified. Moreover, a manR-overexpressing strain showed significantly increased beta-mannanase activity. DNA microarray analysis of the manR-disruptant strain further indicated that when konjac glucomannan is used as the carbon source, ManR positively regulates the gene expression of not only beta-mannanase, but also the enzymes involved in the degradation of galactomannans and glucomannans such as alpha-galactosidase, beta-mannosidase, acetylmannan esterase, and beta-glucosidase. Furthermore, we demonstrated that the presence of 1,4-beta-D-mannobiose increased the expression of the endo-beta-mannanase gene (manG, AO090010000122), and that ManR plays a key role in the inducible expression of manG in A. oryzae. Therefore, we conclude that ManR is a positive regulator of the beta-mannan utilization system in A. oryzae. This is the first study to identify a transcriptional regulator of this system in eukaryotic cells. (C) 2012 Elsevier Inc. All rights reserved.