Heterochromatin heterogeneity in Hypostomus prope unae (Steindachner, 1878) (Siluriformes, Loricariidae) from Northeastern Brazil

Paulo Roberto Affonso,A L Dias,L Giuliano-Caetano,Jamille Bitencourt

doi:10.3897/compcytogen.v5i4.1149

Abstract

Cytogenetic analyses using C-banding and chromosomal digestion by several restriction enzymes were carried out in four populations (named A, B, C and D) of Hypostomus prope unae (Loricariidae, Hypostominae) from Contas river basin, northeastern Brazil. These populations share 2n=76 and single NORs on the second metacentric pair but exclusive karyotype forms for each locality. Populations A and B presented conspicuous terminal and interstitial heterochromatic blocks on most of acrocentric chromosomes and equivalent to NORs with differences in both position and bearing pair. Population D showed evident marks at interstitial regions and interspersed with nucleolar region while population C presented interstitial and terminal heterochromatin segments, non-coincident with NORs. The banding pattern after digestion with the endonucleases Alu I, Bam HI, Hae III and Dde I revealed a remarkable heterogeneity within heterochromatin, allowing the identification of distinctive clusters of repeated DNA in the studied populations, besides specific patterns along euchromatic regions. The analysis using restriction enzymes has proved to be highly informative, characterizing population differences and peculiarities in the genome organization of Hypostomus prope unae.

Highlights

Restriction enzymes (RE) represent a powerful tool for studies about DNA organization (Lima-de-Faria et al 1980)
Within the genus Hypostomus Lacépède,1803, heterochromatin can be associated to heteromorphic chromosomes (Cereali et al 2008; Kavalco et al 2004, 2005), sex chromosomes (Artoni et al 1998) and polymorphism cases (Rubert et al 2008)
Populations A and B bear conspicuous terminal and interstitial marks in 17 chromosomal pairs as well as centromeric and NOR-associated heterochromatin, they differ in relation to C-bands position or bearing pair (Figs 2, 3)

Summary

Introduction

Restriction enzymes (RE) represent a powerful tool for studies about DNA organization (Lima-de-Faria et al 1980). Species of this genus usually present a remarkable variability in both distribution and composition of heterochromatin (Artoni and Bertollo 1999) These data refer to C-banding and/or fluorochrome staining while studies using enzymatic digestion have not been reported in the genus or the family Loricariidae so far

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Conclusion