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

Author:
Ogawa, Masahiro, Kobayashi, Tetsuo, Koyama, Yasuji
Source:
Fungal genetics and biology 2012 v.49 no.12 pp. 987-995
ISSN:
1087-1845
Subject:
Aspergillus oryzae, DNA microarrays, DNA-binding proteins, alpha-galactosidase, beta-glucosidase, beta-mannosidase, carbon, eukaryotic cells, fungi, galactomannans, gene expression, genes, konjac mannan, microarray technology, mutants, transcription (genetics), zinc
Abstract:
Fungal endo-β-mannanases (β-mannanases) are widely used as industrial enzymes; however, no transcriptional regulator of β-mannanases has been identified in fungi or other eukaryotic cells to date. To identify a transcriptional regulator of β-mannanases in Aspergillus oryzae, a gene-disruptant library of transcriptional regulators was screened for mutants exhibiting reduced β-mannanase activity by using konjac glucomannan as the substrate, and ManR, a Zn(II)₂Cys₆ type DNA binding protein was identified. Moreover, a manR-overexpressing strain showed significantly increased β-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 β-mannanase, but also the enzymes involved in the degradation of galactomannans and glucomannans such as α-galactosidase, β-mannosidase, acetylmannan esterase, and β-glucosidase. Furthermore, we demonstrated that the presence of 1,4-β-d-mannobiose increased the expression of the endo-β-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 β-mannan utilization system in A. oryzae. This is the first study to identify a transcriptional regulator of this system in eukaryotic cells.