Insights regarding sirtuin-dependent gene regulation during white koji production

ABSTRACT

White koji, a solid-state culture of Aspergillus luchuensis mut. kawachii using grains such as rice and barley, is used as a source of amylolytic enzymes and citric acid for the production of shochu, a traditional Japanese distilled spirit. We previously characterized changes in gene expression that affect the properties of white koji during the shochu production process; however, the underlying regulatory mechanisms were not determined. We then characterized the NAD⁺-dependent histone deacetylase sirtuin, an epigenetic regulator of various biological phenomena, in A. l. mut. kawachii and found that sirtuin SirD is involved in expression of α-amylase activity and citric acid accumulation. In this addendum study, we measured the NAD⁺/NADH redox state and found that the NAD⁺ level and NAD⁺/NADH ratio decrease during koji production, indicating that sirtuin activity declines in the late stages of koji culture. By comparing these results with transcriptomic data obtained in our previous studies, we estimate that approximately 35% of the gene expression changes during white koji production are SirD dependent. This study provides clues to the mechanism of gene expression regulation in A. l. mut. kawachii during the production of white koji.

KEYWORDS:

• Aspergillus luchuensis mut. kawachii
• white koji
• gene regulation
• NAD⁺-dependent histone deacetylase
• sirtuin

Acknowledgments

We thank Kazuki Mori and Aoi Miyamoto for helpful discussions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

T.F. and M.G. designed the experiments, conducted the research and data analysis, and wrote the manuscript.

Data availability

The datasets analyzed during the current study are available in the Gene Expression Omnibus (accession numbers GSE58454 and GSE132729) [4, 5].

Additional information

Funding

This work was supported by JSPS KAKENHI grants (No. 24580116 to M.G. and No. 19K05773 to T.F.) and a Nagase Science and Technology Foundation award to T.F.