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Open Access Research article

B chromosome in the beetle Coprophanaeus cyanescens (Scarabaeidae): emphasis in the organization of repetitive DNA sequences

Sarah Gomes de Oliveira1, Rita Cassia de Moura2 and Cesar Martins1*

Author affiliations

1 Department of Morphology, Bioscience Institute, UNESP - Sao Paulo State University, Botucatu, SP, 18618-970, Brazil

2 Department of Biology, Biological Sciences Institute, UPE - Pernambuco State University, Recife, PE, 50100-130, Brazil

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Citation and License

BMC Genetics 2012, 13:96  doi:10.1186/1471-2156-13-96

Published: 6 November 2012

Abstract

Background

To contribute to the knowledge of coleopteran cytogenetics, especially with respect to the genomic content of B chromosomes, we analyzed the composition and organization of repetitive DNA sequences in the Coprophanaeus cyanescens karyotype. We used conventional staining and the application of fluorescence in situ hybridization (FISH) mapping using as probes C0t-1 DNA fraction, the 18S and 5S rRNA genes, and the LOA-like non-LTR transposable element (TE).

Results

The conventional analysis detected 3 individuals (among 50 analyzed) carrying one small metacentric and mitotically unstable B chromosome. The FISH analysis revealed a pericentromeric block of C0t-1 DNA in the B chromosome but no 18S or 5S rDNA clusters in this extra element. Using the LOA-like TE probe, the FISH analysis revealed large pericentromeric blocks in eight autosomal bivalents and in the B chromosome, and a pericentromeric block extending to the short arm in one autosomal pair. No positive hybridization signal was observed for the LOA-like element in the sex chromosomes.

Conclusions

The results indicate that the origin of the B chromosome is associated with the autosomal elements, as demonstrated by the hybridization with C0t-1 DNA and the LOA-like TE. The present study is the first report on the cytogenetic mapping of a TE in coleopteran chromosomes. These TEs could have been involved in the origin and evolution of the B chromosome in C. cyanescens.

Keywords:
Chromosomal rearrangements; Heterochromatin; Multigene families; Supernumerary chromosome; Transposable elements