Metabolic reprogramming driven by mpSte11A deletion redirects carbon flux toward overproduction of Monascus pigments in Monascus ruber

Monascus spp., a food fermentation microorganism, produced valuable secondary metabolites including Monascus pigments (MPs) which served as natural food colorants. However, rational metabolic engineering to enhance MPs production remained limited by the lack of regulatory targets that govern metabolic branching. Mitogen-activated protein kinase cascades, particularly the STE20-STE11-STE7 core module, regulated fungal growth and metabolism, but their roles in MPs biosynthesis remain unexplored. In this study, we functionally characterized MpSte11A, the first STE11 homolog identified in Monascus ruber M7, through bioinformatic analysis and genetic manipulation. Most importantly, deletion of mpSte11A triggered a profound metabolic shift, which resulted in a 22-fold increase in MPs production. Integrated transcriptomic and metabolomic analysis revealed that MpSte11A functioned as a metabolic gatekeeper where its deletion redirected carbon flux from primary metabolism to MP biosynthesis by controlling the TCA cycle. These findings not only elucidated the signaling role of the MAPK cascade in Monascus ruber M7 specialized metabolism but also provided a robust strategy for re-engineering carbon partitioning to maximize the output of high-value secondary metabolites in filamentous fungal cell factories.