The Drosophila heat shock hsr-omega gene: an allele frequency cline detected by quantitative PCR.
The hsr-omega gene of Drosophila melanogaster produces RNA products both constitutively and at elevated levels in response to heat stress. A single-nucleotide difference in this gene that has been detected using denaturing gradient gel electrophoresis (DGGE) is responsible for an hsr-omegaa/b polymorphism, and selection experiments have indicated an association between the hsr-omegaa allele and susceptibility to heat stress. Since allele frequency estimates for population surveys using PCR and DGGE for single flies would be relatively time-consuming and expensive, we here develop a quantitative competitive-PCR method using mass-grind genomic DNA preparations for this purpose. Geographical and temporal variation of allele frequency at the hsr-omega locus in Australian populations of D. melanogaster are examined. Regular samples from a southern population through a summer season suggested stability of hsr-omegaa frequency. Field populations sampled from a approximately 2,250 km north-south transect along eastern Australia revealed a strong positive association between the frequency of hsr-omegaa and latitude, and marked spatial autocorrelation. Using appropriate analyses, strong association between population differences in hsr-omegaa frequencies and differences in temperature and rainfall measures, after controlling for latitudinal differences, support the idea that the cline in hsr-omegaa frequency may be attributable to some form of climatic selection.
McColl
G
G
Department of Biological Sciences, Monash University, Victoria, Australia.
McKechnie
S W
SW
D000483:Alleles; D000818:Animals; D004331:Drosophila melanogaster / Q000235:genetics*; D005787:Gene Frequency; D006360:Heat-Shock Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction
D006360:Heat-Shock Proteins