Basal hsp70 expression levels do not explain adaptive variation of the warm- and cold-climate O and O gene arrangements of Drosophila subobscura.

Background: Drosophila subobscura exhibits a rich inversion polymorphism, with some adaptive inversions showing repeatable spatiotemporal patterns in frequencies related to temperature. Previous studies reported increased basal HSP70 protein levels in homokaryotypic strains for a warm-climate arrangement compared to a cold-climate one. These findings do not match the similar hsp70 genomic organization between arrangements, where gene expression levels are expected to be similar.

Expression of thermal tolerance genes in two Drosophila species with different acclimation capacities.

Heat tolerance increases at higher acclimation temperatures in D. melanogaster, but not in D. subobscura.

Chromosomal inversions promote genomic islands of concerted evolution of Hsp70 genes in the Drosophila subobscura species subgroup.

Heat-shock (HS) assays to understand the connection between standing inversion variation and evolutionary response to climate change in Drosophila subobscura found that "warm-climate" inversion O exhibits non-HS levels of Hsp70 protein like those of "cold-climate" O after HS induction. This was unexpected, as overexpression of Hsp70 can incur multiple fitness costs. To understand the genetic basis of this finding, we have determined the genomic sequence organization of the Hsp70 family in four different inversions, including O , O , O and O , using as outgroups the remainder of the subobscura species subgroup, namely Drosophila madeirensis and Drosophila guanche.