THE HEAT-SHOCK GENE HSP83 OF DROSOPHILA-AURARIA - GENOMIC ORGANIZATION, NUCLEOTIDE-SEQUENCE, AND LONG ANTIPARALLEL COUPLED ORF (LAC ORF)

The genomic organization of the hsp83 gene of Drosophila auraria, a fa r-eastern endemic species belonging to the montium subgroup of the mel ano-gaster species group, is presented here. Based on in situ hybridiz ation on polytene chromosomes, cDNA and genomic clone mapping, nucleot ide sequencing, and genomic clone mapping, nucleotide sequencing, and genomic. Southern analysis, hsp83 is shown to be present as a single-c opy gene at locus 64B on the 3L chromosome arm in D. auraria. This gen e is organized into two exons separated by a 929-bp intron. The first exon represents the mRNA leader sequence and is not translated, while the coding region, having a length of 2,151 bp, is solely included in the second exon. Nucleotide sequence comparisons of D. auraria hsp83 w ith homologous sequences from other organisms show high conservative o f the coding region (88-92% identity) in the genus Drosophila, in addi tion to the conserved genomic organization of two-exons-one-intron, of comparable size and arrangement. A phylogenetic tree based on the pro tein sequences of homologous genes from representative organisms is in accord with the accredited phylogenetic position of D. auraria. In th e hsp83 gene region, a second case of long antiparallel coupled open r eading frames (LAC ORFs) for this species was found. The antiparallel to the hsp83 gene ORF is 1,554 bases long, while the two ORFs overlap has a size of 1,548 bp. The anti-hsp83 ORF does not show significant h omology to any known gene sequences. In addition, no similar LAC ORF s tructures were found in homologous gene regions of other organisms.