The Zn(II)2-Cys6-type zinc finger protein AoKap7 is involved in the growth, oxidative stress and kojic acid synthesis in Aspergillus oryzae

Although the kojic acid gene cluster in <i>Aspergillus oryzae</i> was identified in 2010, the functions of neighbouring genes remain poorly understood. Here, we characterise <i>Aokap7</i>, a gene adjacent to this cluster that encodes a novel nucleus-localised zinc finger protein without transcriptional activation activity. Disruption of <i>Aokap7</i> markedly accelerated spore germination, hyphal growth, and conidial formation, but impaired kojic acid production. Overexpression of <i>kojR</i> or <i>laeA</i> restored kojic acid production in the <i>Aokap7</i> disruption strain, whereas their disruption abolished it, indicating that <i>Aokap7</i> regulates kojic acid production by <i>kojR</i> and <i>laeA</i>. Furthermore, disrupting <i>Aokap7</i> in the <i>AozfA</i> overexpression or disruption strains reversed their kojic aicd production, suggesting that <i>Aokap7</i> acts downstream of <i>AozfA</i>. The <i>Aokap7</i> mutant also exhibited reduced expression of reactive oxygen species (ROS)-scavenging genes and heightened oxidative stress sensitivity. Biochemical assays revealed that <i>Aokap7</i> preferentially binds to the motif 5'-CGGCTCGG-3', and directly interacts with the <i>AoGPX1</i> promoter. Disruption of <i>AoGPX1</i> increased the sensitivity of <i>A. oryzae</i> to oxidative stress. Our findings elucidate the pivotal role of <i>Aokap7</i> in coordinating growth, oxidative stress response and kojic acid production, advancing understanding of the regulatory network of kojic acid synthesis in <i>A. oryzae</i>.