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.
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.
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.