Chromosomal location and reorganization of the 45S and 5S rDNA in the Brachyscome lineariloba complex (Asteraceae)
1997
Adachi, J. (Kobe Univ. (Japan). Faculty of Science) | Watanabe, K. | Fukui, K. | Ohmido, N. | Kosuge, K.
The chromosomal locations of the 45S (18S-5.8S-26S) and 5S ribosomal DNA in the Brachyscome lineariloba complex and two related species have been determined by the use of multicolor fluorescence in situ hydridization (McFish). The Brachyscome lineariloba complex includes five cytodemes with 2n=4, 8, 10, 12 and 16. Each of the 5S and 45S rDNA loci occurs at two sites on chromosomes in cytodemes with 2n=4. While in cytodemes with 2n=8, 10, 12 and 16, the number of 5S rDNA sites increases from four to eight paralleled to the genomic addition of diploid (4 chromosomes) or haploid (2 chromosomes) dosage. Of the 5S rDNA sites, only one pair is major, except for the cytodeme with 2n=10. The remaining 5S rDNA sites are minor and seem to have reduced the unit number of the 5S rDNA during the successive genomic additions. The 45S rDNA site is detected only at two nucleolar organizing regions in all cytodemes regardless of successive genomic addition. The loss or diminution of 45S rDNA sequences seem to have proceeded more rapidly than 5S rDNA sequences in the B. lineariloba complex
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