A Drosophila heat shock locus with a rapidly diverging sequence but a conserved structure

Area of Science:

• Molecular biology
• Genetics
• Evolutionary biology

Background:

• Cytological studies suggest homology between heat shock loci 93D (D. melanogaster) and 2-48B (D. hydei).
• Sequence homology between these loci is minimal, challenging direct comparison.

Purpose of the Study:

• To compare homologous heat shock loci in D. melanogaster and D. hydei using cloned DNA sequences.
• To investigate sequence divergence and conserved features despite low overall homology.

Main Methods:

• Comparative analysis of cloned DNA sequences from heat shock loci.
• Characterization of predominant transcripts, including size, start sites, and termination points.
• Examination of unique gene portions and short tandem repeat sequences for homology.

Main Results:

• Both loci produce transcripts of similar size and number, initiating at conserved start sites.
• Short tandem repeat sequences show high intra-species conservation but significant inter-species divergence.
• Unique gene portions exhibit divergence but retain some conserved sequence regions.
• Cytoplasmic transcripts are spliced and polyadenylated but lack significant open reading frames.

Conclusions:

• Significant sequence divergence exists between these homologous heat shock loci.
• Conserved features, including transcript characteristics and some unique sequence regions, suggest functional conservation.
• The study highlights the complex interplay of divergence and conservation in homologous gene loci.