Elucidating the role of KojR in transcriptional regulation of carbon metabolism for kojic acid biosynthesis in Aspergillus oryzae

DNA-binding transcription factors are broadly characterized as proteins that bind to specific sequences within genomic DNA and modulate the expression of downstream genes. This study focused on KojR—a transcription factor involved in the metabolism of kojic acid, which is an organic acid synthesized in Aspergillus oryzae and is known for its tyrosinase-inhibitory properties. However, the regulatory mechanism underlying KojR-mediated kojic acid synthesis in remains unclear. Hence, we aimed to obtain a comprehensive identification of KojR-associated genes using genomic Systematic Evolution of Ligands by Exponential enrichment (gSELEX-Seq) and RNA-Seq. During the genome-wide exploration of KojR-binding sites via gSELEX-Seq and identification of KojR-dependent differentially expressed genes (DEGs) using RNA-Seq, we confirmed that KojR directly regulates kojT, as was previously reported. We also observed that kojA expression, which may be controlled by KojR, was significantly reduced in a ΔkojR strain. Notably, no binding of KojR to the kojA promoter region was detected. Furthermore, certain KojR-dependent DEGs identified in the present study were associated with enzymes implicated in the carbon metabolic pathway of A. oryzae. This strongly indicates that KojR plays a central role in carbon metabolism in A. oryzae.