Proteomic identification of differentially expressed and phosphorylated proteins in epidermis involved in larval-pupal metamorphosis of Helicoverpa armigera

BACKGROUND: Metamorphosis is an important process in the life cycle of holometabolous insects and is regulated by insect hormones. During metamorphosis, the epidermis goes through a significant transformation at the biochemical and molecular levels. RESULTS: To identify proteins and phosphoproteins involved in this process, we separated and compared epidermal protein profiles between feeding larvae and metamorphically committed larvae using two-dimensional gel electrophoresis and Pro-Q Diamond Phosphoprotein Staining. Sixty-one spots showing differential expression and/or phosphorylation were analyzed by mass spectrometry and eighteen proteins were proved related to larval-pupal transformation. Eight of them were further examined at the mRNA level by Reverse Transcription Polymerase Chain Reaction (RT-PCR) and two of them were examined at the protein level by Western blot. Calponin was highly expressed in the metamorphic epidermis and phosphorylated by protein kinase C. CONCLUSION: Our results suggest that the expression and phosphorylation of these proteins may play important roles in coordinating the biochemical processes involved in larval-pupal metamorphosis.