Journal of Heredity Advance Access originally published online on December 23, 2004
Journal of Heredity 2005 96(2):155-160; doi:10.1093/jhered/esi018
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Brief Communication |
In Situ Chromosomal Localization of rDNA Sites in "Safed Musli" Chlorophytum Ker-Gawl and Their Physical Measurement by Fiber FISH
From the Cytogenetics Division, Central Institute of Medicinal and Aromatic Plants, Lucknow226 015, India (U. C. Lavania, Basu, and Srivastava); Laboratory of Plant Molecular Genetics, Osaka Kyoiku University, Kashiwara, Osaka 582-8582, Japan (Mukai); and Department of Botany, University of Lucknow, Lucknow226 007, India (S. Lavania).
Address correspondence to U. C. Lavania at the address above, or e.mail: lavania{at}cimap.res.in.
Fluorescence In Situ Hybridization (FISH) technique has been applied on somatic chromosomes and extended DNA fibers in the medicinally important species of Chlorophytum to elucidate physical localization and measurement of the rDNA sites using two rRNA multigene families homologous to 45S and 5S rDNA. The two species of Chlorophytum, namely C. borivillianum and C. comosum, both with 2n = 28, reveal diversity for copy number and localization of rDNA sites. C. borivillianum is comprised of five 45S-rDNA sites:one each in the secondary constriction region of chromosomes 7, 8, 9; one in the subtelomeric region of the short arm of chromosome 2 and the telomeric region of the short arm of chromosome 12; and one 5S-rDNA site in the subtelomeric region of the long arm of chromosome 1. In C. comosum, there are three 45S-rDNA sites (one each in the short arm of chromosomes 12, 13, and 14) and two 5S-rDNA sites (in the secondary constriction regions of chromosomes 2 and 13). Fiber FISH analysis conducted on extended DNA fibers revealed variation in the size of continuous tandem strings for the two r-DNA families. Taking the standard value of native B DNA equivalent to 3.27 kb for 1 µm, it was estimated that the physical size of continuous DNA strings is of the order of
90 kb, 180 kb, and 300 kb for 45S-rDNA and of the order of 60 kb, 150 kb for 5S-rDNA in C. comosum, grossly in correspondence to their respective physical sizes at metaphase.