Proteomic and phosphoproteomic analysis at diapause initiation in the cotton bollworm, Helicoverpa armigera

Diapause is a period of developmental arrest that allows a species to adapt to unfavorable conditions. Many insect species reduce metabolic activity and then enter diapause at a certain stage in their life cycles. The cotton bollworm, Helicoverpa armigera, will be destined for pupal diapause when larvae are reared under short daylengths and low temperature. The brain is an important organ for diapause decision, and some signaling molecules from the brain of diapause-destined individuals are released into the hemolymph to regulate diapause. In this study, we performed 2-D gel-based comparative proteomic and phosphoproteomic analyses to search for differentially expressed proteins between nondiapause- and diapause-destined pupal brains. A total of 79 proteins and 23 phosphoproteins showed significant differences between these two groups, and 41 proteins and 10 phosphoproteins were identified by MALDI-TOF/TOF MS. Further, gene expression patterns in diapause- and nondiapause-destined pupal brains were confirmed by RT-PCR or Western blot analysis. These differentially expressed proteins act in the metabolic change, stress response, and signal transduction pathways at early pupal stage for diapause initiation. Thus, these identified proteins may depress metabolism in diapause-destined pupae to lead the insect to enter developmental arrest.