Key regulatory genes of pyruvate homeostasis in Trogoderma granarium: Transcriptional responses to cold- and starvation-induced diapause

Pyruvate serves as a central regulatory point in glucose metabolism by directing flux between glycolysis, tricarboxylic acid cycle, and gluconeogenesis in response to energy demands. Because diapause lacks external nutrient intake, it offers a model to study how pyruvate regulation supports metabolic adaptation under energy limitation. The khapra beetle, a destructive feeder of stored grains and cereal products, ranks among the world's 100 worst invasive species, employing facultative diapause as a survival strategy under adverse conditions. In this study, the genes encoding essential enzymes involved in pyruvate homeostasis—including pyruvate kinase (TgPK), pyruvate dehydrogenase E1 (TgPDH), and phosphoenolpyruvate carboxykinase (TgPEPCK)—were identified and characterized in the khapra beetle. Their expression levels were analyzed across distinct phases of cold- and starvation-induced diapause. The highest abundance of TgPK was recorded during the diapause phase after cold exposure, suggesting a potential need for sustained glycolytic flux to generate substrates. Its peak expression occurred in the post-diapause phase of starvation-induced diapause, suggesting that elevated pyruvate levels from glycolysis coincide with the resumption of feeding. Although TgPDH expression was elevated at the onset of diapause, its decline in the following weeks and post-diapause phase may indicate a transient increase in energy production to support metabolic adjustments for diapause initiation. A significant abundance of TgPEPCK was observed during the diapause phase of both induced diapauses, compared to the pre- and post-diapause phases, which may indicate ongoing gluconeogenesis at this stage. Additional researches are required to investigate the functional roles of these genes and associated diapause pathways.