Mutual regulation of novel transcription factors RsrD and RsrE positively modulates the production of raw-starch-degrading enzyme in Penicillium oxalicum

• Published in: Applied and environmental microbiology 2024-08, Vol.90 (8), p.e0039024
• Main Authors: Guo, Hao, Mo, Li-Xiang, Luo, Xue-Mei, Zhao, Shuai, Feng, Jia-Xun
• Format: Article
• Language: English
• Subjects: Amylases; Amylases - genetics; Amylases - metabolism; Binding; Enzymes; Epistasis; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungi; Gene expression; Gene Expression Regulation, Fungal; Gene regulation; Genes; Genetics and Molecular Biology; Leucine; Leucine zipper proteins; Penicillium - enzymology; Penicillium - genetics; Penicillium - metabolism; Penicillium oxalicum; Promoter Regions, Genetic; Starch; Starch - metabolism; Transcription factors; Transcription Factors - genetics; Transcription Factors - metabolism; α-Amylase
• ISSN: 0099-2240; 1098-5336; 1098-5336
• DOI: 10.1128/aem.00390-24

Filamentous fungi can produce raw-starch-degrading enzyme, however, regulation of production of raw-starch-degrading enzyme remains poorly understood thus far. Here, two novel transcription factors raw-starch-degrading enzyme regulator D (RsrD) and raw-starch-degrading enzyme regulator E (RsrE) were identified to participate in the production of raw-starch-degrading enzyme in . Individual knockout of and in the parental strain Δ resulted in 31.1%-92.9% reduced activity of raw-starch-degrading enzyme when cultivated in the presence of commercial starch from corn. RsrD and RsrE contained a basic leucine zipper and a Zn2Cys6-type DNA-binding domain, respectively, but with unknown functions. RsrD and RsrE dynamically regulated the expression of genes encoding major amylases over time, including raw-starch-degrading glucoamylase gene and α-amylase gene . Interestingly, RsrD and RsrE regulated each other at transcriptional level, through binding to their own promoter regions; nevertheless, both failed to bind to the promoter regions of and , as well as the known regulatory genes for regulation of amylase gene expression. RsrD appears to play an epistatic role in the module RsrD-RsrE on regulation of amylase gene expression. This study reveals a novel regulatory pathway of fungal production of raw-starch-degrading enzyme.IMPORTANCETo survive via combating with complex extracellular environment, filamentous fungi can secrete plant polysaccharide-degrading enzymes that can efficiently hydrolyze plant polysaccharide into glucose or other mono- and disaccharides, for their nutrients. Among the plant polysaccharide-degrading enzymes, raw-starch-degrading enzymes directly degrade and convert hetero-polymeric starch into glucose and oligosaccharides below starch gelatinization temperature, which can be applied in industrial biorefinery to save cost. However, the regulatory mechanism of production of raw-starch-degrading enzyme in fungi remains unknown thus far. Here, we showed that two novel transcription factors raw-starch-degrading enzyme regulator D (RsrD) and raw-starch-degrading enzyme regulator E (RsrE) positively regulate the production of raw-starch-degrading enzyme by . RsrD and RsrE indirectly control the expression of genes encoding enzymes with amylase activity but directly regulate each other at transcriptional level. These findings expand diversity of gene expression regulation in fungi.