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Evolution and structure of 5S rDNA loci in allotetraploid Nicotiana tabacum and its putative parental species.
Heredity (Edinb) 2002; 88(1):19-25H

Abstract

Nicotiana tabacum (tobacco) is an allotetraploid derived from ancestors of the modern diploids, N. sylvestris and N. tomentosiformis. We identified and characterized two distinct families of 5S ribosomal DNA (rDNA) in N. tabacum; one family had an average 431 bp unit length and the other a 646 bp unit length. In the diploid species, N. sylvestris and N. tomentosiformis, the 5S rDNA unit lengths are 431 bp and 644 bp respectively. The non-coding spacer sequence of the short unit in tobacco had high sequence homology to the spacer of N. sylvestris5S rDNA, while the longer spacer of tobacco had high homology with the 5S spacer of N. tomentosiformis. This suggests that the two 5S families in tobacco have their origin in the diploid ancestors. The longer spacer sequence had a GC rich sub-region (called the T-genome sub-region) that was absent in the short spacer. Pulsed field gel analysis and fluorescent in situ hybridization to tobacco metaphase chromosomes showed that the two families of 5S rDNA units are spatially separate at two chromosomal loci, on chromosomes S8 (short family) and T8 (long family). The repeat copy number at each chromosomal locus showed heterogeneity between different tobacco cultivars, with a tendency for a decrease in the copy number of one family to be compensated by an increase in the copy number of the second family. Sequence analysis reveals there is as much diversity in 5S family units within the diploid species as there is within the T and S-genome 5S family units respectively, suggesting 5S diversification within each family had occurred before tobacco speciation. There is no evidence of interlocus homogenization of the two 5S families in tobacco. This is therefore substantially different to 18-26S rDNA where interlocus gene conversion has substantially influenced most sequences of S and T genome origin; possible reasons are discussed.

Authors+Show Affiliations

Institute of Biophysics, Academy of Sciences of the Czech Republic, CZ-61265 Brno, Czech Republic.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11813102

Citation

Fulnecek, J, et al. "Evolution and Structure of 5S rDNA Loci in Allotetraploid Nicotiana Tabacum and Its Putative Parental Species." Heredity, vol. 88, no. 1, 2002, pp. 19-25.
Fulnecek J, Lim KY, Leitch AR, et al. Evolution and structure of 5S rDNA loci in allotetraploid Nicotiana tabacum and its putative parental species. Heredity (Edinb). 2002;88(1):19-25.
Fulnecek, J., Lim, K. Y., Leitch, A. R., Kovarík, A., & Matyásek, R. (2002). Evolution and structure of 5S rDNA loci in allotetraploid Nicotiana tabacum and its putative parental species. Heredity, 88(1), pp. 19-25.
Fulnecek J, et al. Evolution and Structure of 5S rDNA Loci in Allotetraploid Nicotiana Tabacum and Its Putative Parental Species. Heredity (Edinb). 2002;88(1):19-25. PubMed PMID: 11813102.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Evolution and structure of 5S rDNA loci in allotetraploid Nicotiana tabacum and its putative parental species. AU - Fulnecek,J, AU - Lim,K Y, AU - Leitch,A R, AU - Kovarík,A, AU - Matyásek,R, PY - 2001/09/07/received PY - 2001/09/18/accepted PY - 2002/1/29/pubmed PY - 2002/4/24/medline PY - 2002/1/29/entrez SP - 19 EP - 25 JF - Heredity JO - Heredity (Edinb) VL - 88 IS - 1 N2 - Nicotiana tabacum (tobacco) is an allotetraploid derived from ancestors of the modern diploids, N. sylvestris and N. tomentosiformis. We identified and characterized two distinct families of 5S ribosomal DNA (rDNA) in N. tabacum; one family had an average 431 bp unit length and the other a 646 bp unit length. In the diploid species, N. sylvestris and N. tomentosiformis, the 5S rDNA unit lengths are 431 bp and 644 bp respectively. The non-coding spacer sequence of the short unit in tobacco had high sequence homology to the spacer of N. sylvestris5S rDNA, while the longer spacer of tobacco had high homology with the 5S spacer of N. tomentosiformis. This suggests that the two 5S families in tobacco have their origin in the diploid ancestors. The longer spacer sequence had a GC rich sub-region (called the T-genome sub-region) that was absent in the short spacer. Pulsed field gel analysis and fluorescent in situ hybridization to tobacco metaphase chromosomes showed that the two families of 5S rDNA units are spatially separate at two chromosomal loci, on chromosomes S8 (short family) and T8 (long family). The repeat copy number at each chromosomal locus showed heterogeneity between different tobacco cultivars, with a tendency for a decrease in the copy number of one family to be compensated by an increase in the copy number of the second family. Sequence analysis reveals there is as much diversity in 5S family units within the diploid species as there is within the T and S-genome 5S family units respectively, suggesting 5S diversification within each family had occurred before tobacco speciation. There is no evidence of interlocus homogenization of the two 5S families in tobacco. This is therefore substantially different to 18-26S rDNA where interlocus gene conversion has substantially influenced most sequences of S and T genome origin; possible reasons are discussed. SN - 0018-067X UR - https://www.unboundmedicine.com/medline/citation/11813102/Evolution_and_structure_of_5S_rDNA_loci_in_allotetraploid_Nicotiana_tabacum_and_its_putative_parental_species_ L2 - http://dx.doi.org/10.1038/sj.hdy.6800001 DB - PRIME DP - Unbound Medicine ER -