Mechanistic Insights from Transcriptomics: How the Glucose Transporter gltp1 Gene Knockout Enhances Monascus Pigment Biosynthesis in M. ruber CICC41233

This study's objective was to evaluate the effect of the glucose transporter GLTP1 in <i>Monascus ruber</i> CICC41233 on <i>Monascus</i> pigment biosynthesis. The <i>gltp1</i> gene in <i>M. ruber</i> 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 <i>gltp1</i> gene knockout strain <i>M. ruber</i> 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 <i>gltp1</i> 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 <i>Monascus</i> pigment synthesis. This study provides novel insights into the molecular link between carbon transport, signaling, and <i>Monascus</i> pigments in <i>Monascus ruber</i>.