ANTIFREEZE PROTEIN DOES NOT CONFER COLD TOLERANCE TO TRANSGENIC DROSOPHILA-MELANOGASTER

Fish antifreeze proteins (AFPs) have been reported by some researchers to prolong the viability of tissues, organs, and embryos under hypoth ermic conditions, while others have observed no such effect or even AF P-mediated cryotoxicity. We examined the influence of Type III AFP fro m Atlantic wolffish on cold tolerance in a whole animal model system, transgenic Drosophila. The activity of the AFP, transgenically express ed under the transcriptional control of the female-specific yp1 and yp 2 promoters and secreted into fly hemolymph, was confirmed through the rmal hysteresis and differential scanning calorimetry measurements as well as through observations of ice crystal morphology. To cold exposu re trials, at 0 degrees C and at -7 degrees C, transgenic adult flies of both sexes exhibited greater survival than nontransgenic controls e ven though the antifreeze was only produced in females. We attribute t hese observations to the expression of the xanthine dehydrogenase mark er gene used to identify transgenics, rather than the production of AF P. Type III AFP therefore appears unable to enhance survival of adult Drosophila under hypothermic conditions. (C) 1995 Academic Press, Inc.