Abstract
BackgroundThe Pyrrhocoris apterus (Insecta: Heteroptera) adults attain high levels of cold tolerance during their overwintering diapause. Non-diapause reproducing adults, however, lack the capacity to express a whole array of cold-tolerance adaptations and show relatively low survival when exposed to sub-zero temperatures. We assessed the competence of non-diapause males of P. apterus for responding to heat- and cold-stresses by up-regulation of 70 kDa heat shock proteins (Hsps) and the role of Hsps during repair of heat- and cold-induced injury.Principal FindingsThe fragments of P. apterus homologues of Hsp70 inducible (PaHsp70) and cognate forms (PaHsc70) were cloned and sequenced. The abundance of mRNA transcripts for the inducible form (qPCR) and corresponding protein (Western blotting) were significantly up-regulated in response to high and low temperature stimuli. In the cognate form, mRNA was slightly up-regulated in response to both stressors but very low or no up-regulation of protein was apparent after heat- or cold-stress, respectively. Injection of 695 bp-long Pahsp70 dsRNA (RNAi) caused drastic suppression of the heat- and cold-stress-induced Pahsp70 mRNA response and the up-regulation of corresponding protein was practically eliminated. Our RNAi predictably prevented recovery from heat shock and, in addition, negatively influenced repair of chilling injuries caused by cold stress. Cold tolerance increased when the insects were first exposed to a mild heat shock, in order to trigger the up-regulation of PaHsp70, and subsequently exposed to cold stress.ConclusionOur results suggest that accumulation of PaHsp70 belongs to a complex cold tolerance adaptation in the insect Pyrrhocoris apterus.
Highlights
Insects evolved impressive strategies for survival at sub-zero body temperatures [1]
Our results suggest that accumulation of PaHsp70 belongs to a complex cold tolerance adaptation in the insect Pyrrhocoris apterus
Based on the structural homology with known proteins from other insects and based on the expression responses to the heat shock stimulus, the fragments were named Pahsp70 and Pahsc70 and the sequences were deposited in NCBI GenBank under accession numbers FJ386397 and FJ386398, respectively
Summary
Insects evolved impressive strategies for survival at sub-zero body temperatures [1]. It has been proposed recently that heat shock proteins (Hsps) contribute to the cold tolerance of insects [8]. Hsp proteins are found in all organisms and their structure and function are highly conserved [11] They were discovered as being induced by heat shock, i.e. a brief exposure to non-lethal temperatures above the optimum for growth and development [12]. Non-diapause reproducing adults, lack the capacity to express a whole array of coldtolerance adaptations and show relatively low survival when exposed to sub-zero temperatures. We assessed the competence of non-diapause males of P. apterus for responding to heat- and cold-stresses by up-regulation of 70 kDa heat shock proteins (Hsps) and the role of Hsps during repair of heat- and cold-induced injury
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