The hsp70 locus of Drosophila auraria (montium subgroup) is single and contains copies in a conserved arrangement

The restriction endonuclease pattern of a number of hsp70-homologous clones isolated from a library of heat shock cDNA from Drosophila auraria, a spec ies belonging to the montium subgroup of the melanogaster species group, re veals two types of clones, A and B, differing in a single restriction site. Both types, as well as hsp70-specific probes derived from both hsp70 loci of Drosophila melanogaster, hybridize in situ with a single band at region 32 A of the 2L polytene arm, indicating a clustered organization of the hsp 70 gene copies in D. auraria. The longest type B clone was sequenced and it was found that one strand contains an open reading frame (ORF) exhibiting great identity with a previously described hsp70 gene of D. auraria (now de noted as type A) and with its counterparts of D. melanogaster, while its se cond strand, unlike the type A clone, does not contain a long antiparallel coupled ORF (LAC ORF) because of a base substitution resulting in a prematu re stop codon. After additional data had been derived from isolation and ch aracterization of hsp70-homologous genomic clones, together with Southern a nalysis of genomic DNA, we found that two hsp70 gene copies are present at the above locus of D. auraria with an inverted tandem repeat organization, while the presence of a third hsp70 gene is not clearly evident. The above results are compared with those observed at the homologous loci of some mel anogaster subgroup species (D. melanogaster and its sibling species), in wh ich, however, the hsp70 locus is duplicated, and with the more distantly re lated Dipteran Anopheles albimanus.