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Nuclear DNA Content, Base Composition, and Cytogenetic Characterization of Christia obcordata

Hamidou F. Sakhanokho, Nurul Islam-Faridi
Journal of the American Society for Horticultural Science 2013 v.138 no.3 pp. 205-209
Christia, chromosome number, flow cytometry, fluorescence in situ hybridization, genes, house plants, leaves, loci, nuclear genome, nucleolus organizer region, ribosomal DNA, ribosomal RNA, root tips
Christia obcordata is an intriguing small-sized house plant with unusual and attractive features such as its striped leaves. Because very little is known about the plant, we conducted an investigation of its genome and chromosomes. The number of chromosomes was determined using a protoplast technique to prepare root tip chromosome spread and was found to be 2n = 2x = 20. Flow cytometry was used to determine nuclear DNA content (1C = 0.65 pg = 634.4 Mb) for C. obcordata and AT/GC composition was shown to be AT%= 62.8% ± 0.0%and GC% = 37.2% ± 0.0%. Finally, fluorescent in situ hybridization was used to locate ribosomal RNA gene families in C. obcordata. Ribosomal RNA gene families, viz. 18S-28S and 5S rDNA, are unique cytomolecular landmarks that provide valuable information about the evolutionary organization of a genome. We have identified one locus each of 18S-28S and 5S rDNA. The 18S-28S rDNA is located in the subterminal position on the secondary constriction region [also known as the nucleolus organizer region (NOR)] and the 5S rDNA is located interstitially close to a centromeric position. The basic information gathered in this study on C. obcordata will be helpful in understanding the genetics of this species.