Expression of the 70 kDa Heat shock protein family in Alpine freshwater chironomids (Diptera, Chironomidae) under natural conditions

Abstract

Chironomidae represent up to 100% of the fauna of Alpine streams. Because they survive stress conditions such as extremely low<br />temperature (annual mean <4 °C), these animals represent a good organism model to analyze the relationship between adaptation to<br />cold and expression of stress proteins such as the 70 kDa Heat shock protein family. Fourth instar larvae of ten species of coldstenothermal<br />chironomids (Pseudodiamesa branickii, Diamesa latitarsis, D. laticauda, D. cinerella, D. insignipes, D. zernyi, D.<br />vaillanti, Orthocladius (O.) frigidus, O. (Euorthocladius) thienemanni and Paratrichocladius nivalis) were collected in a glacier-fed<br />stream in NE Italy at two stations (1300 and 2600 m a.s.l.) and in two seasons (summer 2005 and spring 2006). Immunodetection<br />and quantification of the relative levels of Hsp70 family were performed via Western blot analysis. Significantly different levels of<br />Hsp70 were detected among species. The highest amounts were recorded in P. nivalis and D. insignipes, the lowest in P. branickii.<br />Within the genus Diamesa, lower levels of Hsp70 were observed in the most cold-stenothermal species than in the less coldstenothermal<br />ones. These differences may be explained by different species autoecology. The results provide information on<br />biochemical strategies of alpine midges to face cold temperatures under natural conditions and new insights into their possible<br />response to global warming

THERMAL STRESS INDUCES HSP70 PROTEINS SYNTHESIS IN LARVAE OF THE COLD STREAM NON‐BITING MIDGE Diamesa cinerellaMeigen

“…This clearly indicates that such midges employ the HSP70 protein family in their physiological adaptation to cold waters of their natural habitat. This was also detected in other alpine cold stenothermal midges (Lencioni et al, 2009) and in the Antarctic midge B. antarctica (Rinehart et al, 2006). The strategy of expressing hsp genes continuously is adopted by other several organisms belonging to animals and protists living in very cold environments of polar and temperate zones to avoid protein denaturation due to low temperatures (Joplin et al, 1990;Yocum et al, 1991;Denlinger et al, 1992;Lee et al, 1995;Feder and Hofmann, 1999;Carpenter and Hofmann, 2000;La Terza et al, 2001;Place and Hofmann, 2005).…”

“…During this period, the quantity of suspended sediments reaches 350 mg/l and the mean summer water temperature is 3.2 • C, whereas in winter, when the substrate is partially frozen, it gets down to subzero (Boscaini et al, 2004). Therefore, the growing season is brief and the zoobenthic community is composed mainly of chironomids of the genus Diamesa that has the physiological (Lencioni et al, , 2008 and biochemical (present study; Lencioni et al, 2009) adaptations to withstand environmental stresses such as low temperature of water. In the stream reach at lower altitude (1260 m a.s.l.…”

“…Among these midges, Diamesinae is the best adapted subfamily to colonize cold waters, with the genus Diamesa Meigen, 1835 accounting for up to 100% of the fauna in glacial streams (Füreder, 1999;Lods-Crozet et al, 2001;Lencioni and Rossaro, 2005). As the cold sthenotermal midges belonging to Diamesa are potentially threatened by global warming in alpine area, they are appropriate animals to study the adaptive strategies evolved to survive temperature increasing within the scenario of climate change and glacier retreating (Lencioni et al, 2008(Lencioni et al, , 2009. Previous studies highlighted that midges from cold Alpine streams employ the 70 kDa heat shock family in their physiological adaptation to cold waters of their natural habitat (Lencioni et al, 2009) and as a response to heat stress exposure (Bernabò et al, 2011).…”

The chironomid‐temperature relationship: expression in nature and palaeoenvironmental implications

“…Few environmental factors have a larger influence on insect metabolism than temperature (Ward & Stanford, 1979; Sweeney, 1984; Danks, 2007). A number of studies suggest changes in the structure, function and activity of enzymes and enzymatic processes in chironomids as a response to different temperatures (Detra & Collins, 1986; Simcic, 2005; Lencioni, Boschini & Rebecchi, 2009). Other studies have demonstrated that temperature increases chironomid respiration rate (Edwards, 1958; Johnson & Brinkhurst, 1971; Konstantinov, 1971; McFarlane & McLusky, 1972; Ripley, 1980; Iwakuma, 1986; Bairlein, 1989; Hamburger & Dall, 1990; Hamburger, Dall & Lindegaard, 1994; Simcic, 2005; Brodersen et al , 2004; Lencioni et al , 2008).…”

Cold adaptive potential of chironomids overwintering in a glacial stream

“…Pseudodiamesa branickii and D. cinerella represent two exceptions because they both show constitutive expression of the inducible isoform of 70‐kDa HSP genes under natural conditions (control samples). These results are consistent with previous data obtained in this laboratory, highlighting the synthesis and accumulation of the HSP70 proteins under natural conditions in both species (Lencioni et al ., ). Presumably, these midges have evolved a molecular mechanism to maintain hsp function without interfering with central metabolism and growth (which requires the synthesis of other proteins), as well as a control mechanism involving environmental or physiological signals that maintains the hsp70 gene in a constant transcriptionally active state, with the aim of preserving protein homeostasis of the cell, as previously observed in Antarctic fish (Place & Hofmann, ).…”