Expression of heterochromatin protein 1 affects citric acid production in Aspergillus luchuensis mut. kawachii

September A putative methyltransferase, LaeA, controls citric acid production through epigenetic regulation of the citrate exporter gene, cexA, in the white koji fungus Aspergillus luchuensis mut. kawachii. In this study, we investigated the role of another epigenetic regulator, heterochromatin protein 1, HepA, in citric acid production. The AhepA strain exhibited reduced citric acid production in liquid culture, although to a lesser extent compared to the AlaeA strain. In addition, the AlaeA AhepA strain showed citric acid production similar to the AlaeA strain, indicating that HepA plays a role in citric acid production, albeit with a less-significant regulatory effect than LaeA. RNA-seq analysis revealed that the tran-scriptomic profiles of the AhepA and AlaeA strains were similar, and the expression level of cexA was reduced in both strains. These findings suggest that the genes regulated by HepA are similar to those regulated by LaeA in A. luchuensis mut. kawachii. However, the reductions in citric acid production and cexA expression observed in the disruptants were mitigated in rice koji, a solid-state culture. Thus, the mechanism by which citric acid production is regulated differs between liquid and solid cultivation. Further investigation is thus needed to understand the regulatory mechanism in koji.(c) 2023, The Society for Biotechnology, Japan. All rights reserved.