Drosophila melanogaster is polymorphic for a specific repeated (CATA) sequence in the regulatory region of hsp23

To identify sequence variation associated with a selection response for hea t tolerance in Drosophila melanogaster, we sequenced 1400 bp of the heat sh ock protein 23 gene (hsp23) promoter region in four heat-selected and two c ontrol lines. The region was found to be variable for a specific (CATA) rep eated sequence, and the sequence CTT seems to be a hot spot for mutation. T he repeated tetranucleotide sequence was located in several short repeats s cattered throughout the entire region. Similar variable repeats are also lo cated downstream the of hsp23 gene in the intergenic region between hsp23 a nd hsp27. We detected nine different hsp23 alleles. Their frequencies in th e selection and control lines seemed to be mainly determined by genetic dri ft. The function of the CATA repeats is not yet known, though these regions have homology to SAR elements located in the intergenic region between two hsp70 genes, suggesting a similar function. (C) 1999 Elsevier Science B.V. All rights reserved.