Skip to main content

Chromosome map of the Siamese cobra: did partial synteny of sex chromosomes in the amniote represent “a hypothetical ancestral super-sex chromosome” or random distribution?

Singchat, Worapong, O’Connor, Rebecca, Tawichasri, Panupong, Suntronpong, Aorarat, Sillapaprayoon, Siwapech, Suntrarachun, Sunutcha, Muangmai, Narongrit, Baicharoen, Sudarath, Peyachoknagul, Surin, Chanhome, Lawan, and others. (2018) Chromosome map of the Siamese cobra: did partial synteny of sex chromosomes in the amniote represent “a hypothetical ancestral super-sex chromosome” or random distribution? BMC Genomics, 19 . Article Number 939. ISSN 1471-2164. (doi:10.1186/s12864-018-5293-6) (KAR id:71533)

Abstract

Background

Unlike the chromosome constitution of most snakes (2n=36), the cobra karyotype shows a diploid chromosome number of 38 with a highly heterochromatic W chromosome and a large morphologically different chromosome 2. To investigate the process of sex chromosome differentiation and evolution between cobras, most snakes, and other amniotes, we constructed a chromosome map of the Siamese cobra (Naja kaouthia) with 43 bacterial artificial chromosomes (BACs) derived from the chicken and zebra finch libraries using the fluorescence in situ hybridization (FISH) technique, and compared it with those of the chicken, the zebra finch, and other amniotes.

Results

We produced a detailed chromosome map of the Siamese cobra genome, focusing on chromosome 2 and sex chromosomes. Synteny of the Siamese cobra chromosome 2 (NKA2) and NKAZ were highly conserved among snakes and other squamate reptiles, except for intrachromosomal rearrangements occurring in NKA2. Interestingly, twelve BACs that had partial homology with sex chromosomes of several amniotes were mapped on the heterochromatic NKAW as hybridization signals such as repeat sequences. Sequence analysis showed that most of these BACs contained high proportions of transposable elements. In addition, hybridization signals of telomeric repeat (TTAGGG)n and six microsatellite repeat motifs ((AAGG)8, (AGAT)8, (AAAC)8, (ACAG)8, (AATC)8, and (AAAAT)6) were observed on NKAW, and most of these were also found on other amniote sex chromosomes.

Conclusions

The frequent amplification of repeats might involve heterochromatinization and promote sex chromosome differentiation in the Siamese cobra W sex chromosome. Repeat sequences are also shared among amniote sex chromosomes, which supports the hypothesis of an ancestral super-sex chromosome with overlaps of partial syntenies. Alternatively, amplification of microsatellite repeat motifs could have occurred independently in each lineage, representing convergent sex chromosomal differentiation among amniote sex chromosomes.

Item Type: Article
DOI/Identification number: 10.1186/s12864-018-5293-6
Uncontrolled keywords: amniote, synteny, repeat sequences, sex chromosome, snake
Subjects: Q Science > QR Microbiology
Divisions: Divisions > Division of Natural Sciences > Biosciences
Depositing User: Darren Griffin
Date Deposited: 04 Jan 2019 10:19 UTC
Last Modified: 04 Mar 2024 16:17 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/71533 (The current URI for this page, for reference purposes)

University of Kent Author Information

  • Depositors only (login required):

Total unique views for this document in KAR since July 2020. For more details click on the image.