Thermal response of Heterorhabditis bacteriophora transformed with the Caenorhabditis elegans hsp70 encoding gene

A heat-shock response is induced when cells are exposed to temperatures slightly higher than their optimal physiological temperature. This response is based on the synthesis of heat-shock proteins encoded by the heat-shock genes. A correlation between the increased thermotolerance and production of 70-kDa heat-shock protein (hsp70) has been observed in many organisms. We tested this hypothesis by transferring a Caenorhabditis elegans heat-inducible hsp70 A-encoding gene into the entomopathogenic nematodes Heterorhabditis bacteriophora Hp88. Successful transformation of the gene was confirmed by Southern blot hybridization and polymerase chain reaction. Our blot studies showed that the transgenic nematodes contained five to ten copies per genome of the introduced hsp70 A gene. hsp70 mRNA transcripts were detected in both wild-type and transgenic nematodes. Transcripts increased severalfold in transgenic nematodes upon heat shock. Infective juveniles of both transgenic and wild-type nematodes that exposed to a sublethal heat treatment (35 degrees C) for 2 h followed by a normally lethal heat treatment (40 degrees C) for 1 h. More than 90% of transgenic nematodes survived heat treatment, compared to 2% to 3% of the wild-type strain. Our observations establish that overexpression of hsp70 A gene resulted an enhanced thermotolerance in the transgenic nematodes. The transgenic nematodes displayed normal growth and development.