Chromosomal localization of 18S and 5S rDNA using FISH in the genus Tor (Pisces, Cyprinidae)
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Dual color fluorescence in situ hybridization (FISH) was performed to study the simultaneous chromosomal localization of 18S and 5S ribosomal genes in the genus Tor for the first time. The 18S and 5S rDNAs in four Tor species were amplified, sequenced and mapped on the metaphase chromosomes. The number and distribution of 18S and 5S rDNA clusters were examined on metaphase chromosome spreads using FISH. The specimens of T. chelynoides, T. putitora and T. progeneius showed six bright fluorescent signals of 18S rDNA and T. tor exhibited ten such signals. The 5S rDNA signals were present only on one pair of chromosomes in all the four Tor species. Ag-NORs were observed on two pairs of chromosomes in T. chelynoides, T. putitora, T. progeneius and four pairs in T. tor. Comparison of the observed 18S rDNA FISH signals and Ag-NORs strongly suggested a possible inactivation of NORs localized at the telomeres of a subtelocentric and telocentric chromosome pairs in all four species. The 5S rDNA contained an identical 120 bp long coding region and 81 bp long highly divergent non-transcribed spacers in all species examined. 18S and 5S rDNA sequencing and chromosomal localization can be a useful genetic marker in species identification as well as phylogenetic and evolutionary studies.
Keywords18S 5S FISH rDNA Tor
The authors are thankful to the Department of Biotechnology, the Ministry of Science and Technology, Government of India for funding.
- Almeida-Toledo LF, Ozouf-Costaz C, Foresti F, Bonillo C, Porto-Foresti F, Daniel-Silva MZF (2002) Conservation of the 5S-bearing chromosome pair and co-localization with major rDNA clusters in five species of Astyanax (Pisces, Characidae). Cytogenet Genome Res 97(3–4):229–233. doi: 10.1159/000066609 CrossRefPubMedGoogle Scholar
- Bertollo LAC, Takahashi CS, Moreira-Filho O (1978) Cytotaxonomic consideration on Hoplias lacrdae (Pisces, Erythrinidae). Braz J Genet 1:103–120Google Scholar
- Gromicho M, Coutanceau JP, Ozouf-Costaz C, Collares-Pereira MJ (2006) Contrast between extensive variation of 28S rDNA and stability of 5S rDNA and telomeric repeats in the diploid-polyploid Squalius alburnoides complex and in its maternal ancestor Squalius pyrenaicus (Teleostei, Cyprinidae). Chromosom Res 14:297–306. doi: 10.1007/s10577-006-1047-4 CrossRefGoogle Scholar
- Khuda-Bukhsh AR, Nayak K (1982) Karyomorpological studies in two species of hill stream fishes from Kashmir, India: occurrence of a high number of chromosomes. Chromosom inf Sci (Japan) 33:12–14Google Scholar
- Kushwaha B, Srivastava SK, Nagpure NS, Ogale SN, Ponniah AG (2001) Cytogenetic studies in two species of mahseer, Tor khudree and Tor mussullah (Cyprinidae, Pisces) from India. Chromosom Sci 5:47–50Google Scholar
- Lakra WS (1996) Cytogenetic studies on endangered fish species: karyotypes of three species of mahseers, Tor putitora, T. tor and T. khudree (Cyprinidae Pisces). Cytobios 85:205–218Google Scholar
- Martins C, Wasko AP (2004) Organization and evolution of 5S ribosomal DNA in the fish genome. In: Williams CR (ed) Focus on Genome Research. Nova Science Publishers, Hauppauge, pp 289–319Google Scholar
- Nederby-Nielson J, Hallenberg C, Frederiksen S, Sorensen PD, Lomholt B (1993) Transcription of human 5S rRNA genes is influenced by an upstream DNA sequence. Nucleic Acids Res 26:3631–3636Google Scholar
- Sambrook J, Russell I (2001) Molecular cloning: a laboratory manual, 3rd edn. Cold Spring Harbor Laboratory Press, Plainsveiw New YorkGoogle Scholar
- Sarkar UK, Srivastava SM (2000) Endangered Mahseer in North East India. In: Ponniah AG, Sarkar UK (eds) Fish Biodiversity of North East India, NBFGR, NATP publ, Lucknow, India, pp 95–96Google Scholar