Distinct pattern of restriction endonuclease digestion on the heterochromatic components of Sarcophagid flies: An evidence of species-specific divergence of heterochromatin

Abstract

Heterochromatin in the genome plays a vital role in species differentiation and evolution. To characterize and unravel molecular composition of the heterochromatic regions of the genome in dipteran flies, especially in Sarcophagids, different banding techniques have been used previously which established the banding pattern of constitutive heterochromatin. The present study is an attempt to further explore the base specificity of rather highly condensed C-banded regions of chromosomes using restriction enzyme (RE) digestion along with Giemsa staining, in search of species-specific targets of RE digestion. Different REs such as Apa I, Cla I, Eco RI, Hind III, Hae III and Pvu II have been used to characterize the heterochromatic regions of two Sarcophaga species, i.e., Sarcophaga ruficornis and Sarcophaga argyrostoma. Some of the constitutively heterochromatic regions remain intensely stained indicating no targets for the enzyme cleavage, while some of the heterochromatic areas in both the species show remarkable and distinct digestion sites after the treatment of REs. In S. ruficornis, Hind III digests the entire autosomes including the pericentromeric regions and the sex chromosome; while Hae III and Pvu II selectively digest autosomes and sex chromosome. While in S. argyrostoma, Cla I digests the entire autosomes including the pericentromeric regions; Hind III and Hae III selectively digests autosomes and sex chromosomes. These findings suggest the presence of distinctive enzyme digestion targets on the heterochromatin, which may provide important evidence for the differential base specificity that were previously found to be constitutive in nature.