Effects of manR disruption and overexpression on Aspergillus oryzae gene expression

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 and the manR-overexpressing 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. Therefore, we conclude that ManR is a positive regulator of the β-mannan utilization system in A. oryzae. manR disruptant, manR-overexpressing strain and A. oryzae RkuptrP2-1∆AF/P (derivative of A. oryzae RIB40) were cultivated in minimal medium containing 1% konjac glucomannan as the sole carbon source. After 6 h cultivation, total RNAs from the mycelia were extracted, and DNA microarray analysis was carried out. The analysis of manR disruptant was conducted with 4 biological replications, the analysis of manR overexpressing strain was conducted with 3 biological replications.