The actin loci in the genus Drosophila: establishment of chromosomal homologies among five nearctic species of the Drosophila obscura group by in situ hybridization

Abstract

The actin genes of five nearctic species of the Drosophila obscura group were mapped by in situ hybridization, using the 5C actin gene of D. melanogaster as a probe. In all species but D. azteca eight actin loci were observed variously dispersed over all five (A- E) chromosomal elements. In D. azteca ten actin hybridization sites were found; four of which most probably originated by duplications or by transposition events. Although the five nearctic species differ from all other Drosophila species of the D. obscura group so far studied in the number of loci as well as in the chromosomal distribution and location of the actin loci, the uniformity of the main pattern with six actin loci throughout the genus Drosophila reinforces the hypothesis that the chromosomal elements have maintained their essential identities during the course of evolution. Our findings are in accordance with the conclusion that the nearctic D. obscura species have differentiated from a common ancestor of the palearctic species and that they belong to two distinct subgroups, the pseudoobscura and the affinis subgroups.

Muller “Elements” inDrosophila: How the Search for the Genetic Basis for Speciation Led to the Birth of Comparative Genomics

“…The use of in situ hybridization of DNA to polytene chromosomes has been a powerful approach to verify the conservation of Muller elements, but it also provided valuable insights into the mechanisms of chromosomal rearrangements and laid the groundwork for anchoring genome sequence contigs to the polytene chromosomes. Initially, small numbers of DNA probes were hybridized to the polytene chromosomes of different species, adding support for the conservation of Muller elements ( Steinemann 1982 , 1984 ; Whiting et al 1989 ; Terol et al 1991 ; Segarra and Aguade 1992 ; Papaceit and Juan 1993 ; Rohde et al 1994 , 1995 ; Bondinas et al 2001 , 2002 ; Santos et al 2010 ).…”

In situlocalization of the evolutionary conserved Cpy/Cty gene in the subfamily Chironominae (Chironomidae, Diptera): establishment of chromosomal homologies

“…For tracing the chromosome rearrangements involved in the evolution process several approaches were proposed (Bondinas et al. 2001): specifically by examining the banding patterns of larval polytene chromosomes and analyzing the configuration of hybrid polytene chromosomes.…”

“…In genus Drosophila other approach was applied – in situ hybridization of labelled DNA sequences to their complementary DNAs of the polytene chromosomes of different species (Steinemann et al. 1984; Loukas and Kafatos 1986; Bondinas et al. 2001).…”