Evolution and arrangement of the hsp70 gene cluster in two closely related species of the virilis group of Drosophila

Abstract

To investigate the genetic basis of differing thermotolerance in the closely related species Drosophila virilis and Drosophila lummei, which replace one another along a latitudinal cline, we characterized the hsp70 gene cluster in multiple strains of both species. In both species, all hsp70 copies cluster in a single chromosomal locus, 29C1, and each cluster includes two hsp70 genes arranged as an inverted pair, the ancestral condition. The total number of hsp70 copies is maximally seven in the more thermotolerant D. virilis and five in the less tolerant D. lummei, with some strains of each species exhibiting lower copy numbers. Thus, maximum hsp70 copy number corresponds to hsp70 mRNA and Hsp70 protein levels reported previously and the size of heat-induced puffs at 29C1. The nucleotide sequence and spacing of the hsp70 copies are consistent with tandem duplication of the hsp70 genes in a common ancestor of D. virilis and D. lummei followed by loss of hsp70 genes in D. lummei. These and other data for hsp70 in Drosophila suggest that evolutionary adaptation has repeatedly modified hsp70 copy number by several different genetic mechanisms.

Comparative physiological, biochemical, and molecular thermal stress response profiles for two Unionid freshwater mussel species

“…For example, the Pacific oyster (Crassostrea gigas) genome has 88 copies of the HSP70 gene, each with highly variable gene expression profiles in response to cellular stress (Zhang et al, 2012). There is also evidence for species-specific differences in heat shock protein gene copy numbers related to thermal niche in Drosophila species (Evgen'ev et al, 2004).…”

Remarkable Site Specificity of Local Transposition Into the Hsp70 Promoter of Drosophila melanogaster

“…Detection of local insertions with PCR: Drosophila genomic DNA was isolated as described (Evgen'ev et al 2004). Each polymerase chain reaction consisted of 1.25 units of Taq DNA polymerase (Promega, Madison, WI) per probe, 0.1 mg DNA in 30 ml of buffer (Promega), 1.5-2 mm MgCl 2 , 0.2 mm of each dNTP, and 5 pm of each primer.…”

“…DNA manipulations and Southern analysis: Isolation of genomic DNA from adult flies and Southern blot analysis to detect new insertions in Hsp70 genes was performed according to Evgen'ev et al (2004). Five micrograms of each DNA sample was digested with HindIII and BamHI restriction endonucleases.…”

Physical mapping of the Period gene on meiotic chromosomes of South American grasshoppers (Acridomorpha, Orthoptera)

“…Single-copy gene mapping is routinely carried out in several dipteran species such as Drosophila (Ranz et al, 2001;Evgen'ev et al, 2004) and Zaprionus species (Campos et al, 2007) because of the facility of polytene chromosomes. Locating single-copy genes can be useful when comparing karyotypes of species, like the comparison of the Drosophila genus performed by Clark et al (2007), or even to compare karyotypes in close genera or different species and families of dipterans.…”