GlMPC activated by GCN4 regulates secondary metabolism under nitrogen limitation conditions in Ganoderma lucidum

ABSTRACT Fungi actively alter their metabolic and synthetic pathways to cope with changing environmental conditions. The mitochondrial pyruvate carrier (MPC) plays a vital role in transporting pyruvate into mitochondria and regulating carbon metabolic homeostasis. However, the mechanism by which MPC regulates carbon metabolism in response to environmental stress in fungi remains unclear. In this study, yeast one-hybrid library screening assays were employed to screen for transcription factors in Ganoderma lucidum that may interact with GlMPC. General control non-derepressible 4 (GCN4), a key transcription factor responding to nitrogen metabolism, was found to interact with the GlMPC promoter region. This interaction was further confirmed by electrophoretic mobility shift assays and chromatin immunoprecipitation quantitative PCR assays, demonstrating that GCN4 is capable of binding to the GlMPC promoter region in vitro and in vivo. Further results indicated that GCN4 could activate GlMPC expression and participate in regulating the tricarboxylic acid (TCA) cycle and ganoderic acid (GA) biosynthesis under low nitrogen conditions in G. lucidum. These findings revealed a specific regulatory mechanism by which GCN4-activated GlMPC regulates the TCA cycle and secondary metabolism under nitrogen limitation conditions in G. lucidum, providing crucial insights into the regulation of carbon and nitrogen metabolism in fungi. IMPORTANCE Mitochondrial pyruvate carrier (MPC) is a pyruvate transporter that plays a crucial role in regulating the carbon metabolic flow and is considered an essential mechanism for microorganisms to adapt to environmental changes. However, it remains unclear how MPC responds to environmental stress in organisms. General control non-derepressible 4 (GCN4), a key regulator of nitrogen metabolism, plays a pivotal role in the growth and development of fungi. In this study, we report that GCN4 can directly bind to the promoter region and activate the expression of GlMPC, thereby regulating the tricarboxylic acid cycle and secondary metabolism under nitrogen limitation conditions in Ganoderma lucidum. These findings provide significant insights into the regulation of carbon and nitrogen metabolism in fungi, highlighting the critical role of GCN4 in coordinating metabolic adaptation to environmental stresses.