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Kimitaka Yakura, Atsushi Kato, Shigeyuki Tanifuji, Structural Organization of Ribosomal DNA in Four Trillium Species and Paris verticillata, Plant and Cell Physiology, Volume 24, Issue 7, October 1983, Pages 1231–1240, https://doi.org/10.1093/oxfordjournals.pcp.a076637
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Abstract
The rDNA structure in Trillium and Paris was examined by Southern blot hybridizations of EcoRI- and Hind III-digests of nuclear DNA using 32P-rRNAs. Their rDNAs consist of repeating units of the largest lengths ever known for higher plants. Evidence for differentiation of the rDNA structure during evolution was obtained. Each Trillium species has rDNA consisting of a characteristic set of some members out of five rRNA genes of 13.7-, 14.7-, 15.6-, 17.1- and 18.5-kb repeating units. One species has a rDNA structure characterized by much higher relative frequencies of longer-sized rRNA genes, whereas another species has larger amounts of shorter-sized classes. Other two species examined have intermediate-sized genes. There is no direct correspondence of each size class to a certain member of several genomic sets, haploid chromosome complements, which have been denoted on the basis of the affinity in pairing between homologous chromosomes, homologies of chromosomal morphology and external morphology. Paris verticillata, a species in a genus most closely related to Trillium, has two size classes of 15.6 and 17.1 kb, both of which correspond to those found in Trillium. The results indicate that the rDNA structure was rather stable during evolution in these genera.