Ultrastructure of regions containing homologous loci in polytene chromosomes of Drosophila melanogaster and Drosophila subobscura

Abstract

We have used a new approach involving in situ hybridisation and electron microscopy to establish ultrastructural homologies between polytene chromosome regions of Drosophila melanogaster and Drosophila subobscura. Twelve probes were chosen to cover all the chromosomal elements: the myospheroid gene, the collagen type IV gene, the collagen-like gene, the w26 homeobox gene, the beta3 tubulin gene, the kinesin heavy chain gene, the tryptophan hydrolase gene, the Hsp82, Hsp22-26 and Hsp23-28, Hsp68, Hsp70 genes and the beta unit of the F0-F1 ATPase gene. Most of these loci were previously undescribed in D. subobscura and imprecisely located in D. melanogaster. We have demonstrated here, by an ultrastructural analysis of each chromosomal region, that homologous genetic loci tend to show a similar ultrastructure in the two species. With a few exceptions, the structural homology extends to the chromosomal regions surrounding the loci. In some cases, however, no structurally recognisable homology can be seen either in the locus or in its flanking regions.

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

“…As shown in Table 3 (see references therein), these chromosomes share the visible mutations cinnabar and vestigial (melanogaster, subobscura), the loci for amylase (AMY), hexokinase (HK-1), esterase (EST-9), phosphoglucose isomerase (PGI), dipeptidase (DIP-A), β 3 tubulin (β 3 TU), kinesin (KIN), w26 and the Collagen-like gene (melanogaster, subobscura) and element C-specific recombinant DNA probes (melanogaster, subobscura, ambigua, obscura, subsilvestris). Fyrberg et al (1980); f Tobin et al (1980); g Böhm et al (1987); h Loukas et al (1979);i Shneuwly et al (1986); j Cuenca et al (1998);k Segarra et al (1996); l Steinemann et al (1984); m Loukas and Kafatos (1988); n Terol et al (1991); o Molto et al (1992); p Brehm and Krimbas (1990); q Loukas and Vergini (1985) Chromosomal Table 4, the suggestion that all these elements are homologous is supported by banding pattern affinities (ambigua, obscura, tristis, subsilvestris), by the concordance of loci for isocitric dehydrogenase (IDH), alkaline phosphatase (APH), phosphoglucomutase (PGM-1), EST-6, tryptophan hydrolase (TPH), heat shock protein HSP26/22, HSP28/23, HSP82, ecdysone inducible protein (ECIP), accessory male protein (ACP), extra macrochaetae (EMC) and HSP83 (melanogaster, subobscura), of the locus for subobscura,ambigua) and by element-D-specific recombinant DNA probes (melanogaster, subobscura, ambigua, obscura, subsilvestris).…”

“…In recent years a new technique, the "in situ hybridization" of labeled DNA sequences to their complementary DNAs on the polytene chromosomes, has become a powerful method to mark homologous regions of chromosomes (Steinemann 1982;Steinemann et al 1984;Kafatos 1986, 1988;Schneuwly et al 1986;Whiting et al 1989;Steinemann and Steinemann 1990;Terol et al 1991;Visa et al 1991;Molto et al 1992;Segarra and Aguade 1992;Segarra et al 1995Segarra et al , 1996Ranz et al 1997;Cuenca et al 1998). …”

“…by in situ hybridization c The same recombinant DNA probes were used dFyrberg et al (1980); eTobin et al (1980); fCavener (1977); gCuenca et al (1998); h Segarra et al (1996); iRanz et al (1997); jSteinemann et al (1984); kLoukas and Kafatos (1988); lLoukas et al (1979); mMolto et al (1992); nBrehm and Krimbas (1992); oLoukas and Vergini (1985) …”

“…The same letter(c, d or e) in the different species indicates that the same recombinant DNA probes were used fFyrberg et al (1980); gTobin et al (1980); hCavener (1977); iCuenca et al (1998); j Segarra and Aguade (1992); kSegarra et al (1995); l…”

“…cn and vg f, g (subobscura-melanogaster) AMY, PGI, HK-1, PEP-3(=DIP-1), EST-9 a f, g β 3 TU, KIN, w26, Collagen-by in situ hybridization c The same recombinant DNA probes were used dFyrberg et al (1980); eTobin et al (1980); fBöhm et al (1987); gLoukas et al (1979); h Cavener (1977); iCuenca et al (1998); jSteinemann et al (1984); kLoukas and Kafatos (1988) …”