Shock proteins expression during overwintering
Entrance into diapause represents a case of phenotypic plasticity which is based on a deep change of gene transcription. Among others, the transcription of genes coding for heat shock proteins of the family Hsp70 kDa is also altered. We assessed the competence of the bugs for responding to heat- and cold-stresses by up-regulation of these genes.
Body temperature in the insects overwintering in temperate habitats drops often, and for long periods, below 0°C (see Figure). Numerous insect species tolerate temperature extremes under which no vertebrate organism could survive. The key for survival success lies in the seasonal transition into diapause state and stimulation of the adaptive complex which results in high cold and frost tolerance. This complex is in the focus of our research conducted with heteropteran bug, Pyrrhocoris apterus as a model species. Entrance into diapause represents a case of phenotypic plasticity which is based on a deep change of gene transcription. Among others, the transcription of genes coding for heat shock proteins of the family Hsp70 kDa is also altered. We assessed the competence of the bugs for responding to heat- and cold-stresses by up-regulation of these genes. The fragments of P. apterus homologues of Hsp70 kDa inducible and cognate forms were cloned and sequenced. The abundance of mRNA transcripts were assessed using quantitative real time PCR and the abundance of the protein products using the Western blot analysis. The levels of transcripts and protein of the inducible form were significantly up-regulated in response to both, high and low temperature stimuli. We have prepared the dsRNA for inducible form (695bp-long fragment). Injection of the dsRNA (RNAi) into the bugs prior to the temperature stress caused drastic suppression of the heat- and cold-stress-induced trascriptional 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. Our results suggest that the accumulation of Hsp70 kDa belongs to a complex of cold tolerance adaptations in P. apterus.
Koštál V., Tollarová M, Doležel D. (2008) Dynamism in physiology and gene transcription during reproductive diapause in a heteropteran bug, Pyrrhocoris apterus. Journal of Insect Physiology54, 77-88.
Koštál V., Tollarová-Borovanská M. (2009) The 70 kDa Heat Shock Protein Assists during the Reparation of Chilling Injury in the Insect, Pyrrhocoris apterus.PLoS ONE 4 (2), e4546, 1-9.
Tollarová-Borovanská M., Lalouette L., Koštál V. (2009) Insect cold tolerance and repair of chill-injury at fluctuating thermal regimes: Role of 70 kDa heat shock protein expression. Cryo-Letters 30, 312-319.
