THERMAL STRESS INDUCES HSP70 PROTEINS SYNTHESIS IN LARVAE OF THE COLD STREAM NON-BITING MIDGE Diomeso cinerello Meigen

摘要

Laboratory experiments on the cold stenothermal midge Diamesa cinerella (Diptera, Chironomidae) were performed to study the relationship between increasing temperature and heat shock proteins (HSP70) expression at translational level (Western blotting). Thermotolerance of I Vinstar larvae collected in nature at 1.5-4.3 deg C during seasons was analyzed through short-term (1 h at ten different temperatures from 26° C to 35° C) and long-term (1-14 h at 26° C and 1-4 h at 32: C) heat shocks. A high thermotolerance was detected (LT_(50) — 30.9-32.8~ C and LI_(50) — 34.0-37.SC). However, survival decreased consistently with increasing exposure time, especially at higher temperature (LTimeso = 7.64 h at 26° C and LTimeso = 1.73 h at 32C). The relationship between such heat resistance and HSP70 expression appeared evident because a relationship between HSP70 level and larval survival rate ivas generally found. A heat shock response (HSR) ivas consistent only in the summer larvae. The absence of HSRin the other populations coupled with even higher amounts of HSP70 than in summer, led us to hypothesize that other macromolecules and other adaptive mechanisms, apart from biochemical ones, are involved in the response of D. cinerella larvae to high temperature. Altogether these results stressed how in this midge the HSP70 protein family confers resistance against cold, being detected under natural conditions in control larvae collected in all seasons, but also against warm under experimental heat shocks. These results give new insights into possible responses to climate changes in freshwater insects within the context of global warming.