A Novel Major Facilitator Superfamily Transporter Gene Aokap4 Near the Kojic Acid Gene Cluster Is Involved in Growth and Kojic Acid Production in Aspergillus Oryzae

Kojic acid is an important secondary metabolite of industrial importance produced by . The kojic acid gene cluster plays an essential role in kojic acid production, and harbors , and . The deletion of , encoding a major facilitator superfamily (MFS) transporter, did not completely abolish kojic acid production, implying that other transporters are required for the transport of kojic acid. The aim of this study is to look for the transporters involved in kojic acid production. Here, encoding a novel MFS transporter was identified, which was adjacent to in the kojic acid gene cluster. The deletion of contributed to the hyphal growth, conidial production and biomass of . Moreover, is required for heat- and cell-wall-stress tolerance but not oxidative and osmotic stress. The disruption of impaired kojic acid production with the reduced expression of , and . Furthermore, when was deleted in the -disrupted strain, the yield of kojic acid declined to the same level as that of the -deletion mutant, whereas the production of kojic acid was recovered when was overexpressed in the knockout strain, suggesting that acts downstream of . AoKap4 was the second identified MSF transporter involved in kojic acid production after was found a decade ago. This study contributes to a better understanding of the biological roles of the MFS transporter and lays a foundation for future studies on kojic acid synthesis in .