G. Mccoll et Sw. Mckechnie, The Drosophila heat shock hsr-omega gene: An allele frequency cline detected by quantitative PCR, MOL BIOL EV, 16(11), 1999, pp. 1568-1574
The hsr-omega gene of Drosophila melanogaster produces RNA products both co
nstitutively and at elevated levels in response to heat stress. A single-nu
cleotide difference in this gene that has been detected using denaturing gr
adient gel electrophoresis (DGGE) is responsible for an hsr-omega(a/b) poly
morphism, and selection experiments have indicated an association between t
he hsr-omega(a) allele and susceptibility to heat stress. Since allele freq
uency estimates for population surveys using PCR and DGGE for single flies
would be relatively time-consuming and expensive, we here develop a quantit
ative competitive-PCR method using mass-grind genomic DNA preparations for
this purpose. Geographical and temporal variation of allele frequency at th
e hsr-omega locus in Australian populations of D. melanogaster are examined
. Regular samples from a southern population through a summer season sugges
ted stability of hsr-omega(a) frequency. Field populations sampled from a s
imilar to 2,250 km north-south transect along eastern Australia revealed a
strong positive association between the frequency of hsr-omega(a) and latit
ude, and marked spatial autocorrelation. Using appropriate analyses, strong
associations between population differences in hsr-omega(a) frequencies an
d differences in temperature and rainfall measures, after controlling for l
atitudinal differences, support the idea that the dine in hsr-omega(a) freq
uency may be attributable to some form of climatic selection.