Basal hsp70 expression levels do not explain adaptive variation of the warm- and cold-climate O3 + 4 + 7 and OST gene arrangements of Drosophila subobscura.

The equivalent hsp70 mRNA amounts in OST and O3 + 4 + 7 arrangements provide the first evidence of a parallelism between gene expression and genetic organization in D. subobscura lines having these arrangements. This is reinforced by the lack of important differential features in the number and structure of regulatory elements between both arrangements, despite the genetic differentiation observed when the complete 5' and 3' regulatory regions were considered. Therefore, the basal levels of hsp70 mRNA cannot account, in principle, for the adaptive variation of the two arrangements studied. Consequently, further studies are necessary to understand the intricate molecular mechanisms of hsp70 gene regulation in D. subobscura.