Dynamics of heat‐induced thermal stress resistance and hsp70 expression in the springtail, Orchesella cincta

Abstract

Summary 1.The relationship between thermal resistance and expression of inducible heat shock proteins, especially Hsp70, depends on the species and temperature treatments. The induction of Hsp70 has been shown to be essential for heat stress survival in a number of species, yet the maximum protein expression levels do not coincide with peak survival after heat hardening in Drosophila . 2.Here we study the functional relationship between heat-induced expression of the heat shock protein Hsp70, and thermal resistance in adult Orchesella cincta by comparing thermal resistance (survival of 37·4 ° C for 60 min) with Hsp70 gene and protein expression levels, all three measured at time points 2, 4, 6, 23, 27, 49 h after a heat hardening treatment (35·4 ° C for 60 min). 3. Thermotolerance increased over time after heat hardening until 49 h after exposure when the experiment ended. On the other hand the expression of hsp70 messenger RNA reached a peak within the first 2 h and then sharply decreased after 6 h. Within 23 h hsp70 expression was back to control levels. 4. Surprisingly, protein levels of Hsp70 followed thermotolerance and reached the highest levels 49 h after heat hardening. A significant positive association was found between thermotolerance and Hsp70 protein levels, but not with hsp70 mRNA levels. 5. Our results support a strong correlation between Hsp70 expression levels and thermal resistance following a heat hardening treatment. They also show that gene and protein expression follow different dynamics, a difference that may be important for our understanding of the role of candidate genes in functional studies.

Inbreeding interferes with the heat-shock response

“…Several studies have found a positive correlation between heat tolerance and HSP70 expression (Bahrndorff et al, 2009), whereas others have shown opposite or no correlations (Dahlgaard et al, 1998;Bahrndorff et al, 2009Bahrndorff et al, , 2010. Using the same treatments as herein a previous study on B. anynana, we showed that exposure for 2 h to 39 1C strongly increased subsequent heat-stress survival (Franke and Fischer, 2013), suggesting that a positive relationship between HSP70 expression and heat tolerance exists also in our study organism.…”

An intron-containing, heat-inducible stress-70 gene in the millipede Tachypodoiulus niger (Julidae, Diplopoda)

“…On the other hand, the degenerate primers amplify various isoforms, and thus, primers specific to the different isoforms need to be designed on the basis of the sequences obtained with degenerate primers (e.g. as in Bahrndorff et al 2009). …”

“…Köhler et al 1998;Schill et al 2004;Reuner et al 2008;Bahrndorff et al 2009). Degenerate primers targeting the highly conserved nucleotide-binding domain of the hsp70 gene proved useful in amplifying stress protein genes in various animal taxa and subsequent determination of hsp70 nucleotide sequences.…”

“…Any perturbation of the soil biota by pollution may affect decomposition processes and nutrient cycles (Sylvain and Wall 2011). Albeit an ever growing number of sequences in GenBank and research work using hsp70 gene expression as a molecular marker in nematodes (Guisbert et al 2013), lumbricides (Chen et al 2011), slugs and snails (Köhler et al 1998;Reuner et al 2008), and collembolans (Bahrndorff et al 2009;Waagner et al 2012) information about stress genes of the soil fauna is still relatively scarce.…”

“…The approach employs degenerate primers targeting a conserved region of the hsp70 family genes (Bahrndorff et al 2009) that were developed previously for the netted slug Deroceras reticulatum (Köhler et al 1998).…”