Characterizing the symbiotic relationship between Wolbachia (wSpic) and Spodoptera picta (Lepidoptera: Noctuidae): From genome to phenotype

Wolbachia is a genus of symbiotic bacteria prevalent in arthropods, with diverse effects on host reproduction and fecundity; however, it is unclear how Wolbachia modulates the host reproductive system. In this study, a novel Wolbachia strain, wSpic, was identified in the Noctuid moth Spodoptera picta and its effect on the reproduction of this host was investigated. We sequenced and annotated the 1,339,720 bp genome of wSpic. We identified a total of five WO phage regions in the genome and found no evidence of any plasmids associated with wSpic. Evolutionary analysis revealed that wSpic belongs to supergroup B and has undergone horizontal transmission between S. picta and Trichogramma pretiosum, a wasp parasitoid of insect eggs. The removal of Wolbachia by antibiotic treatment resulted in significantly decreased fecundity and abnormal development of S. picta ovaries, but no differences in egg hatching rate. An integrated transcriptome and proteome analysis indicated that major molecular pathways for Wolbachia-induced reproduction fitness benefits include its effects on insect juvenile hormone, vitellogenesis, choriogenesis, and nutritional metabolism. Our findings demonstrate that wSpic plays a critical role in promoting ovary development and sustaining fecundity in S. picta hosts.