Cold tolerance and proline metabolic gene expression in Drosophila melanogaster

Treatment of Drosophila melanogaster adults with an inhibitor of protein sy nthesis led to a decrease in intrinsic cold-shock tolerance, but no differe nce in the rapid cold hardening response, which is apparent only if a perio d at 4 degreesC precedes the cold stress. Increases in energy reserves, inc luding proline, were found in lines of flies selected for resistance to chi lling injury. Since an increase in proline levels has been associated with overwintering in insects, and for salt and cold tolerance in plants, an RNa se protection assay was developed to assess changes in transcript abundance for two genes encoding enzymes important for proline metabolism, pyrroline 5-carboxylate reductase and proline oxidase. The mRNA levels did not chang e in response to low temperature, but the high level of pyrroline 5-carboxy late reductase transcript is consistent with the interpretation that a larg e proline pool is important for Drosophila metabolism and survival during c old stress. (C) 2001 Elsevier Science Ltd. All rights reserved.