Integrative Proteomic and Phosphoproteomic Analyses Revealed Complex Mechanisms Underlying Reproductive Diapause in Bombus terrestris Queens

SIMPLE SUMMARY: Bombus terrestris is one of the most ideal pollinators in the world and brings great economic benefits through the pollination of fruits and vegetables. The huge demand for pollinators, combined with habitat loss, climate change, and pesticide use over the past decades, has resulted in a dramatic decline in wild bumblebee populations and distribution. Hence, the artificial breeding of bumblebees is of great significance and has a broad market prospect. Diapause is an important process in artificial breeding. Although some studies have been carried out on the diapause-related genes of bumblebees, the precise mechanisms affecting the phosphorylation level remain unclear. Here, we performed a new comparison of three diapause-stage expression profiles using isobaric tandem mass tag (TMT)-labeled proteomics and phosphoproteomics. The results provided abundant resources and contributed to a better understanding of the mechanisms underlying the regulation of reproductive diapause in eusocial insects. ABSTRACT: Reproductive diapause is an overwintering strategy for Bombus terrestris, which is an important pollinator for agricultural production. However, the precise mechanisms underlying reproductive diapause in bumblebees remain largely unclear. Here, a combination analysis of proteomics and phosphoproteomics was used to reveal the mechanisms that occur during and after diapause in three different phases: diapause (D), postdiapause (PD), and founder postdiapause (FPD). In total, 4655 proteins and 10,600 phosphorylation sites of 3339 proteins were identified. Diapause termination and reactivation from D to the PD stage were characterized by the upregulation of proteins associated with ribosome assembly and biogenesis, transcription, and translation regulation in combination with the upregulation of phosphoproteins related to neural signal transmission, hormone biosynthesis and secretion, and energy-related metabolism. Moreover, the reproductive program was fully activated from PD to the FPD stage, as indicated by the upregulation of proteins related to fat digestion and absorption, the biosynthesis of unsaturated fatty acids, fatty acid elongation, protein processing in the endoplasmic reticulum, and the upregulation of energy-related metabolism at the phosphoproteome level. We also predicted a kinase–substrate interaction network and constructed protein–protein networks of proteomic and phosphoproteomic data. These results will help to elucidate the mechanisms underlying the regulation of diapause in B. terrestris for year-round mass breeding.