Cold shock elicits expression of heat shock proteins in the flesh fly, Sarcophaga crassipalpis

Abstract

When exposed to brief cold shocks of −10 or −18°C, pharate adults (red eye stage) of the flesh fly, Sarcophaga crassipalpis are unable to eclose as adults. The injury does not cause immediate death: even an 8 h exposure to −18°C allows pharate adult development to proceed to the point of eclosion. Though development continues following cold shock, we observed a dose-dependent decrease in the rate of oxygen consumption, indicating that damage has occurred. The rate of protein synthesis is slow during the first hour after cold shock but quickly recovers. The previously described heat shock proteins, molecular weights 92 and 72 kDa, are expressed in both the brain and integument during recovery from cold shock and are expressed for longer times with increased severity of the cold shock. The cold shock induced 72 kDa protein is immunologically related to the heat shock 70 protein family of Drosophila melanogaster. In addition to the heat shock proteins, three proteins with molecular weights of 78, 45 and 23 kDa, are induced in the integument, but not in the brain, during recovery from cold shock. We previously demonstrated that at high temperatures different developmental stages synthesize two different members of the heat shock 70 protein family, a 65 and a 72 kDa protein. We detect no such developmental switch in response to cold shock. These results demonstrate that heat shock proteins can be induced by extremes of both high and low temperatures but the nature of the stress (heat or cold shock) determines which proteins are induced.