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.

鳞翅目绿僵菌（Metarhizium lepidiotae）是一类具有重要农业价值的昆虫病原真菌。然而，长期传代培养常导致其出现表型退化，具体表现为产孢能力下降与代谢活性受损，但其潜在分子机制仍不甚明晰。阐明该机制对于维持菌株活力、保障生物防治效力至关重要。本研究发现，鳞翅目绿僵菌在长期连续传代培养过程中，产孢能力会出现显著衰退；而通过昆虫宿主传代可有效逆转这一退化表型，实现菌株复壮。随后，我们对原始菌株（XMC-Y）、退化菌株（XMC-T）以及复壮菌株（XMC-F）在培养第7天和第18天的样本开展了比较转录组分析。研究结果显示，退化菌株XMC-T初期会通过增强翻译能力以代偿基础代谢与信号通路的缺陷，但在培养后期会逐渐出现RNA加工系统与翻译机器的严重崩溃。此外，过氧化物酶体通路的显著下调表明其过氧化物酶体生物发生受损、活性氧（ROS）清除能力下降，进而导致抗氧化防御能力降低与细胞内活性氧积累增多。综上，本研究证实RNA调控网络紊乱与氧化稳态失衡是鳞翅目绿僵菌退化的关键分子驱动因素。该研究为大规模生产过程中维持菌株稳定性以及农业生物防治应用提供了重要的理论参考。