Proteomics of the flesh fly brain reveals an abundance of upregulated heat shock proteins during pupal diapause

Abstract

Most molecular work on insect diapause has focused on the expression of unique diapause transcripts, rather than the protein products. Here we present results from a proteomic comparison of diapausing and nondiapausing pupal brains. Proteins extracted from diapausing pupal brains of the flesh fly Sarcophaga crassipalpis were separated by two-dimensional gel electrophoresis and compared with those from nondiapausing pupal brains. Unique proteins and proteins present at different levels of abundance in diapausing and nondiapausing brains were identified by Nano–LC/MS/MS (capillary-liquid chromatography-nanospray tandem mass spectrometry). With this approach and Coomassie staining, we detected 37 diapause-unique or upregulated (⩾2x) proteins, and 43 proteins that were downregulated or not present in diapause. Heat shock proteins (Hsp70 and several small Hsps) were among the most conspicuous brain proteins present in higher amounts during diapause. Brain proteins that were less abundant in diapause included phosphoenolpyruvate synthase, fatty acid binding protein, EG0003.7, and an endonuclease. Our 2-D proteome maps included several additional unknown proteins that were more abundant in either the diapause or nondiapause brains. While the mRNAs encoding some of these proteins (e.g. Hsps) were previously known to be associated with diapause, the other proteins were not known to be linked to diapause, thus suggesting that the proteomic approach nicely supplements the work done at the transcript level.