Mechanistic Insights from Transcriptomics: How the Glucose Transporter gltp1 Gene Knockout Enhances Monascus Pigment...

This study's objective was to evaluate the effect of the glucose transporter GLTP1 in Monascus ruber CICC41233 on Monascus pigment biosynthesis. The gltp1 gene in M. ruber CICC41233 was cloned to construct the overexpression vector pNeo0380-gltp1, resulting in complementation and overexpression strains, and its upstream and downstream homologous arms were used to construct the gene knockout plasmid pHph0380G/Gltp1::hph, resulting in a mutant strain. The results showed that the gltp1 gene knockout strain M. ruber GLTP24 exhibited dramatically accelerated starch degradation and a significant increase (74.1% higher) in the yield of alcohol-soluble pigments compared to the wild-type. Reverse genetic experiments confirmed this phenotype: complementation strains restored wild-type pigment production levels, while overexpression strains showed reduced pigment synthesis. Integrated transcriptomic analyses revealed that gltp1 deletion triggered extensive metabolic reprogramming. This included the downregulation of key components in the carbon-sensing GprD-cAMP/PKA signaling pathway and the concerted upregulation of multiple amino acid metabolic pathways, which supply essential precursors and amino groups for Monascus pigment synthesis. This study provides novel insights into the molecular link between carbon transport, signaling, and Monascus pigments in Monascus ruber.