Transcriptomic Data Suggest Pathways Involved in Conidiation Degeneration and Its Rejuvenate by Passage in the Metarhizium lepidiotae

Metarhizium lepidiotae is an important entomopathogenic fungus with substantial agricultural 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 essential 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 cultivation stages. Moreover, the significant downregulation of the peroxisome pathway indicates impaired peroxisome biogenesis and compromised reactive oxygen species (ROS) metabolic capacity, suggesting a weakened antioxidant defense and a potential increase in oxidative stress. Collectively, these findings indicate that disruptions in RNA regulatory networks and oxidative homeostasis are strongly associated with M. lepidiotae degeneration. This study provides important theoretical insights for maintaining strain stability during large-scale production and agricultural biocontrol applications.