Molecular Biology and Evolution, Vol 16, 1568-1574, Copyright © 1999 by Society for Molecular Biology and Evolution
G McColl and SW McKechnie
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.
ORIGINAL ARTICLE
The Drosophila heat shock hsr-omega gene: an allele frequency cline detected by quantitative PCR
Department of Biological Sciences, Monash University, Victoria, Australia.
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