Abstract
To determine the relationship between protein expression and insect diapause, a proteomic approach was used to investigate the proteins extracted from larvae of the wheat blossom midge Sitodiplosis mosellana Gehin at different developmental stages, including pre-diapause, over-summering diapause, over-wintering diapause and post-diapause. Using 2-DE gels stained with coomassie brilliant blue, about 300 protein spots were detected in the extracts of pre-diapause larvae and 275 for those in each of the other stages. There were 91, 92 and 95 protein spots that showed more than a 2-fold change in abundance in the over-summering diapause, over-wintering diapause and post-diapause stages compared with pre-diapause. Eight protein spots, which showed the greatest difference in the larvae at different stages of diapause, were analyzed using Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Seven of them were successfully identified from their peptide mass fingerprints using the NCBInr database. They were proopiomelanocortin, NADH dehydrogenase subunit 1 and F10F2.5, which were up-regulated or unique to pre-diapause larvae, IKK interacting protein isoform 2 up-regulated in diapause and post-diapause larvae, GA10647-PA unique in over-wintering diapause larvae, purple CG16784-PB isoform B and B0228.6 up-regulated in over-summering and over-wintering diapause larvae. The potential functions of these proteins during wheat blossom midge diapause are discussed.
Highlights
Diapause is a genetically controlled period of developmental arrest that enables insects to survive adverse environmental conditions and synchronize their life cycles with the availability of food (Salama & Miller, 1992; Li et al, 2008)
First dimension gel electrophoresis was performed using an IPGphor isoelectric focusing (IEF) system (Amersham Biosciences, Uppsala, Sweden) by applying 200 μg of protein extract in 250 μl buffer to a 13 cm, pH3-10 linear IPG strip with rehydration at 30 V for 12 h followed by isoelectric focusing at 500 V for 1 h, 1000 V for 1 h and 8000 V for 2 h
Very few proteins that may play a role in insect diapause have been identified
Summary
Diapause is a genetically controlled period of developmental arrest that enables insects to survive adverse environmental conditions and synchronize their life cycles with the availability of food (Salama & Miller, 1992; Li et al, 2008). The wheat blossom midge, Sitodiplosis mosellana (Gehin), is a serious intermittent pest damaging wheat in the northern hemi-sphere (Chen & Ni, 1998; Ding & Guo, 1992). Proteomics is a large-scale study of gene expression at the protein level, which provides a direct measurement of protein expression levels and insight into the activity of relevant proteins. This approach was successfully used in studies of different aspects of entomology, such as induced immunity (Levy et al, 2004), resistance mechanisms (Jiang et al, 2004), molecular pathology (Kaeslin et al, 2005), developmental process (Li et al, 2006; Jia et al, 2007) and diapause (Joplin et al, 1990; Li et al, 2007). The results should facilitate further research into diapause regulation in the wheat blossom midge, which may lead to new ways of effectively controlling this insect pest
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