Chinese cordyceps is a well-known and valuable traditional Chinese medicine that forms after Ophiocordyceps sinensis parasitizes ghost moth larvae. The low natural infection rate of O. sinensis limits large-scale artificial cultivation of Chinese cordyceps, and the invasion process is unclear. To investigate the temporal and spatial regulation when O. sinensis enters ghost moths, we constructed an O. sinensis transformant that stably expresses green fluorescent protein (GFP). Inoculating Thitarodes xiaojinensis larvae with a high concentration of GFP-labeled O. sinensis, we observed that O. sinensis conidia could adhere to the host cuticle within 2 days, germinate penetration pegs within 4 days, and produce blastospores in the host hemocoel within 6 days. The reconstructed three-dimensional (3D) structures of the invasion sites showed that penetration pegs germinated directly from O. sinensis conidia at the joining site with the larval cuticle. Differentiated appressoria or hyphae along the host epicuticle are not required for O. sinensis to invade ghost moths. Overall, the specific invasion process of O. sinensis into its host is clarified, and we provided a new perspective on the invasion process of entomopathogenic fungi.

Melanization and encapsulation are prominent defense responses against microbes detected by pattern recognition receptors of their host insects. In the ghost moth Thitarodes xiaojinensis, an activated immune system can melanize and encapsulate the fungus Cordyceps militaris. However, these responses were hardly detected in the host hemolymph postinfection of another fungus Ophiocordyceps sinensis. The immune interaction between O. sinensis and the host remains largely unknown, which hinders the artificial cultivation of Chinese cordyceps. We found that T. xiaojinensis β-1,3-glucan recognition protein-1 (βGRP1) was needed for prophenoloxidase activation induced by C. militaris. Failure of βGRP1 to recognize O. sinensis is a primary reason for the lack of melanization in the infected host. Lyticase or snailase treatment combined with binding and immunofluorescence detection showed the existence of a protective layer preventing the fungus from βGRP1 recognition. Coimmunoprecipitation and mass spectrometry analysis indicated that βGRP1 interacted with immulectin-8 (IML8) via binding to C. militaris. IML8 promotes encapsulation. This study suggests the roles of T. xiaojinensis βGRP1 and IML8 in modulating immune responses against C. militaris. Most importantly, the data indicate that O. sinensis may evade melanization by preventing βGRP1 recognition.

Ophiocordyceps sinensis, an entomopathogenic fungus, infects larvae from the Lepidoptera: Hepialidae family, forming the valuable Chinese cordyceps. Mycoviruses are widespread across major lineages of filamentous fungi, oomycetes, and yeasts and have the potential to influence fungal biology and ecology. This study aimed to detect mycovirus within O. sinensis by isolating double-stranded RNA from six stains for transcriptomic sequencing and analyzing publicly available transcriptome data from 13 O. sinensis representative samples. Our analysis revealed 13 mycoviruses, with nine reported for the first time in O. sinensis. These mycoviruses are distributed across five families—Partitiviridae, Mitoviridae, Narnaviridae, Botourmiaviridae, Deltaflexiviridae—and two unclassified lineages, Ormycovirus and Vivivirus. This study also revealed frequent coinfections within individual O. sinensis strains and dynamic shifts in viral composition during fungal development. These findings enhance our knowledge of mycovirus diversity within O. sinensis and provide new insights into their taxonomy.

Background: Insect metamorphosis from larvae to pupae is one of the most important stages of insect life history. Relatively comprehensive information related to gene transcription profiles during lepidopteran metamorphosis is required to understand the molecular mechanism underlying this important stage. We conducted transcriptional profiling of the brain and fat body of the cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) during its transition from last instar larva into pupa to explore the physiological processes associated with different phases of metamorphosis. Results: During metamorphosis, the differences in gene expression patterns and the number of differentially expressed genes in the fat body were found to be greater than those in the brain. Each stage had a specific gene expression pattern, which contributed to different physiological changes. A decrease in juvenile hormone levels at the feeding stage is associated with increased expression levels of two genes (juvenile hormone esterase, juvenile hormone epoxide hydrolase). The expression levels of neuropeptides were highly expressed at the feeding stage and the initiation of the wandering stage and less expressed at the prepupal stage and the initiation of the pupal stage. The transcription levels of many hormone (or neuropeptide) receptors were specifically increased at the initiation of the wandering stage in comparison with other stages. The expression levels of many autophagy-related genes in the fat body were found to be gradually upregulated during metamorphosis. The activation of apoptosis was probably related to enhanced expression of many key genes (Apaf1, IAP-binding motif 1 like, cathepsins, caspases). Active proliferation might be associated with enhanced expression levels in several factors (JNK pathway: jun-D; TGF-β pathway: decapentaplegic, glass bottom boat; insulin pathway: insulin-like peptides from the fat body; Wnt pathway: wntless, TCF/Pangolin). Conclusions: This study revealed several vital physiological processes and molecular events of metamorphosis and provided valuable information for illustrating the process of insect metamorphosis from larvae to pupae.