# RNA-Seq Insight into the Impact and Mechanisms of Methyl Donor and Glycine Betaine Osmoprotectant on Polyketide Secondary Metabolism in Monascus purpureus M1

## TL;DR

This study shows how glycine betaine boosts growth and pigment production in a fungus by acting as a methyl donor and osmoprotectant.

## Contribution

The paper reveals novel gene regulatory mechanisms by which glycine betaine enhances polyketide metabolism in Monascus purpureus.

## Key findings

- GB significantly increased red pigment and monacolin K production by 120.08% and 93.4%, respectively.
- Key genes like RPS15, RPS14, and ATP9 were upregulated during later growth phases under GB treatment.
- GB promotes growth and polyketide metabolism by functioning as both a methyl donor and osmoprotectant.

## Abstract

Glycine betaine (GB) serves as both a methyl donor and osmoprotectant in microorganisms, facilitating growth and enhancing metabolic product yields. While the polyketide metabolites from Monascus purpureus, such as Monascus pigments (MPs) and monacolin K (MK), have been extensively studied, the effects of GB on their production and the underlying molecular mechanisms remain insufficiently explored. In this study, various concentrations of GB were added to Monascus purpureus M1 cultures, followed by RNA sequencing, RT-qPCR, differential gene expression analysis, and functional enrichment to investigate the regulatory impact of GB on polyketide metabolism. Protein–protein interaction network analysis identified key upregulated genes, including RPS15, RPS14, RPS5, NDK1, EGD2, and ATP9, particularly during the later growth phases. GB significantly upregulated genes involved in stress response, secondary metabolism, and polyketide biosynthesis. Scanning electron microscopy, HPLC, and UV-Vis spectrophotometry further confirmed that GB promoted both strain growth and polyketide production, with red pigment and MK production increasing by 120.08% and 93.4%, respectively. These results indicate that GB enhances growth and polyketide metabolism in Monascus purpureus by functioning as both a methyl donor and osmoprotectant, offering new insights into optimizing microbial polyketide production and revealing gene regulatory mechanisms by GB in Monascus purpureus.