|Throne, James - Jim|
|Zhu, Kun Yan|
Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2013
Publication Date: 8/6/2014
Publication URL: http://handle.nal.usda.gov/10113/60069
Citation: Chen, H., Zhang, H., Throne, J.E., Zhu, K. 2014. Transcript analysis and expression profiling of three heat shock protein 70 genes in the ectoparasitoid Habrobracon hebetor (Hymenoptera: Braconidae). Insect Science. 21(4):415-428. DOI: http://dx.doi.org/10.111/1744-7917.12032. Interpretive Summary: The Indianmeal moth is a major pest of stored grain and processed commodities. There is a small wasp that does not sting humans but parasitizes the Indianmeal moth, and releasing these parasitic wasps would be an environmentally friendly way to control the Indianmeal moth. But, there is currently no way to store these wasps for when they are needed for controlling the Indianmeal moth. We previously showed that the wasp can enter reproductive diapause (a resting stage where they don’t produce offspring) when reared at low temperature and short photoperiod, and diapausing females have a higher rate of survival during cold storage and lay more eggs after cold storage than nondiapausing females. Heat shock proteins (HSPs) are known as chaperones that help with folding of other proteins when cells are under environmental stresses, and HSPs are essential for cold survival during insect diapause. We identified three HSP genes in the wasp, and characterized their expression levels during exposure to cold. Knowing how heat shock protein genes respond to cold stress may allow enhancement of diapause and prolonging the duration of low-temperature storage of insects by finding ways to artificially control the expression of these genes.
Technical Abstract: Heat shock proteins (HSPs) are known as chaperones that help with folding of other proteins when cells are under environmental stresses. The upregulation of HSPs is essential for cold survival during insect diapause. The ectoparasitoid Habrobracon hebetor, a potential biological control agent, can enter reproductive diapause when reared at low temperature and short photoperiod, and diapausing females have a higher rate of survival during cold storage and higher fecundity after cold storage than nondiapausing females. However, the expression of HSPs during diapause of H. hebetor has not been studied. In this study, we sequenced and characterized the full-length cDNAs of three Hsp70 genes (HhHsp70I, HhHsp70II, and HhHsp70III) from H. hebetor. Their deduced amino acid sequences showed more than 80% identities to their counterparts from other insect species. However, the multiple sequence alignment among the three deduced amino acid sequences of HhHsp70s showed only 46% identities. A phylogenetic analysis of the three HhHsp70s and all other known Hsp70 sequences from Hymenoptera clustered all the Hsp70s into four groups, and the three HhHsp70s were distributed into three different groups. Real-time quantitative PCR analysis showed that the expression of the three HhHsp70 genes in H. hebetor reared at different conditions was quite different. HhHsp70I showed higher relative expression when H. hebetor were reared at 27.5°C than at two lower temperatures (17.5 and 20°C) regardless of the photoperiod, whereas HhHsp70II showed higher expression when H. hebetor were reared at 20°C and 10L:14D than when reared at 17.5°C and either 16L:8D or 10L:14D. In contrast, HhHSP70III was expressed at similar levels regardless of the rearing conditions. These results may suggest functional differences among the three HhHsp70 genes in H. hebetor.