LaeA controls citric acid production through regulation of a citrate exporter encodingcexAinAspergillus luchuensismut.kawachii

Abstract

ABSTRACTThe putative methyltransferase LaeA is a global regulator of metabolic and development processes in filamentous fungi. We characterized the homologouslaeAgenes of the white koji fungusAspergillus luchuensismut.kawachii(A. kawachii) to determine their role in the hyperproduction of citric acid. The ΔlaeAstrain exhibited a significant reduction in citric acid productivity. Cap-analysis gene expression (CAGE) revealed thatlaeAis required for the gene expression of a putative citrate exporter encodingcexA, which is critical for citric acid production. The deficit in the productivity of citric acid by the ΔlaeAstrain was rescued by the overexpression ofcexAto a level comparable with that of thecexA-overexpressing ΔcexAstrain. In addition, chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) analysis indicated that LaeA regulates the expression ofcexAvia methylation levels of the histones H3K4 and H3K9. These results indicate that LaeA is involved in citric acid production through epigenetic regulation ofcexAinA. kawachii.IMPORTANCEA. kawachiihas been traditionally used for production of the distilled spirit shochu in Japan. Citric acid produced byA. kawachiiplays an important role in preventing microbial contamination during the shochu fermentation process. This study characterized homologouslaeAgenes; using CAGE, complementation test, and ChIP-qPCR, it was found thatlaeAis required for citric acid production though regulation ofcexAinA. kawachii. The epigenetic regulation of citrate production elucidated in this study will be useful for controlling the fermentation processes of shochu.