The Basic-Region Helix-Loop-Helix Transcription Factor DevR Significantly Affects Polysaccharide Metabolism in Aspergillus oryzae

Basic-region helix-loop-helix (bHLH) proteins are a superfamily of transcription factors that are often involved in the control of growth and differentiation. Recently, it was reported that the bHLH transcription factor DevR is involved in both asexual and sexual development in Aspergillus nidulans and regulates the conidial melanin production in Aspergillus fumigatus. In this study, we identified and characterized an Aspergillus oryzae gene that showed high similarity with devR of A. nidufans and A. fumigaws (AodevR). In the AodevR-disrupted strain, growth was delayed and the number of conidia was decreased on Czapek-Dox (CD) minimal agar plates, but the conidiation was partially recovered by adding 0.6 M KCI. Simultaneously, the overexpression of AodevR was induced and resulted in extremely poor growth when the carbon source changed from glucose to polysaccharide (dextrin) in the CD agar plate. Scanning electron microscopy (SEM) indicated that the overexpression of AodevR resulted in extremely thin aberrant hyphal morphology. Conversely, the deletion of AodevR resulted in thicker hyphae and in more resistance to Congo red relative to the control strain. Quantitative reverse transcriptase PCR (RT-PCR) further indicated that AoDevR significantly affects chitin and starch metabolism, and importantly, the overexpression of AodevR inhibited the expression of genes related to starch degradation. A yeast one-hybrid assay suggested that the DevR protein possibly interacted with the promoter of amyR, which encodes a transcription factor involved in amylase production. Importantly, AoDevR is involved in polysaccharide metabolism and affects the growth of the A. oryzae strain. IMPORTANCE Aspergillus oryzae is an industrially important filamentous fungus; therefore, a clear understanding of its polysaccharide metabolism and utilization is very important for its industrial utilization. In this study, we revealed that the basic-region helix-loop-helix (bHLH) transcription factor AoDevR is importantly involved in chitin and starch metabolism in A. oryzae. The overexpression of AodevR strongly suppressed the expression of amylase-related genes. The results of a yeast one-hybrid assay suggested that the DevR protein potentially interacts with the promoter of amyR, which encodes a transcription factor involved in amylase production and starch utilization. This study provides new insight for further revealing the regulation mechanism of amylase production in A. oryzae.