Transcriptomic Analysis Reveals the Molecular Mechanisms Underlying Conidiation Degeneration of Metarhizium  lepidiotae
Metarhizium lepidiotae is an important entomopathogenic fungus with substantial agri-cultural value. However, prolonged subculturing often leads to phenotypic degeneration, including reduced conidiation and impaired metabolic activity, while the underlying molecular mechanisms remain poorly understood. Elucidating these mechanisms is es-sential for maintaining strain vitality and ensuring biocontrol efficacy. In this study, we found that M. lepidiotae exhibited a pronounced decline in conidiation during long-term serial subculturing. However, this degenerative phenotype could be effectively reversed by passage through insect hosts, leading to strain rejuvenation. Subsequently, comparative transcriptomic analyses were performed on the original strain (XMC-Y), the degenerated strain (XMC-T), and the rejuvenated strain (XMC-F) at 7 and 18 days of cultivation. Our results revealed that XMC-T initially compensates for defects in basal metabolism and signaling pathways by enhancing translational capacity, but progressively exhibits a profound collapse of RNA-processing systems and the translational machinery at later stages. Moreover, the significant downregulation of the peroxisome pathway indicates impaired peroxisome biogenesis and compromised ROS-scavenging capacity, leading to decreased antioxidant defense and increased intracellular ROS accumulation. Collectively, these findings demonstrate that disruptions in RNA regulatory networks and oxidative homeostasis constitute key molecular drivers of M. lepidiotae degeneration. This study provides important theoretical insights for maintaining strain stability during large-scale production and agricultural biocontrol applications.