Beetle, Dendroides canadensis, antifreeze proteins increased high temperature survivorship in transgenic fruit flies, Drosophila melanogaster

Abstract

Paradoxically, some insects have an increased capacity to survive higher temperatures in winter than summer. Possible contributors to this increased heat tolerance in winter could be their sub-zero adaptations (high polyol concentrations, antifreeze proteins, antifreeze glycolipids, etc.). To investigate if a sub-zero adaptation can increase organismal high temperature survivorship, we tested transgenic fruit flies, Drosophila melanogaster, with antifreeze proteins from the fire-colored beetle, Dendroides canadensis (DAFPs). Transgenic Drosophila melanogaster with individual DAFPs-1 and -4 had increased survivorship compared to control flies after 24 h when placed at 35–36.5 °C. The 24 h ULT50 (Upper Lethal Temperature at which 50% mortality occurred) was calculated to be 36.3 °C for DAFP-1 flies, 36.2 °C for DAFP-4 flies, 35.4 °C for wild-type controls, and 34.9 °C for GAL4 controls. The results indicate that DAFPs may have an alternative function in insects and be a contributor in the unexpected phenomenon of increased higher temperature survivorship in winter.