Long-term cultivation of Panax ginseng cell lines leads to a decreasing synthesis of the biologically active substances used in traditional medicine. To gain insight into the cellular mechanisms which may influence this process, we analyzed variations within the rDNA cluster of the Oriental ginseng cell lines. The cell lines were cultivated for 6 and 24 years; the number of nucleoli and chromosomes was analyzed. The complete 18S rDNA sequences were cloned and sequenced. The nucleotide polymorphism and phylogenetic relations of the sequences were analyzed, and the secondary structures for separate 18S rRNA regions were modeled. The 18S rDNA accumulated mutations during cell cultivation that correlate well with an increase in the number of chromosomes and nucleoli. The patterns of nucleotide diversity are culture-specific and the increasing polymorphism associates with cytosine methylation sites. The secondary structures of some 18S rRNA regions and their interaction can alter during cultivation. The phylogenetic tree topologies are particular for each cell line.The observed alterations in rDNA clusters are associated with a somaclonal variation, leading to changes in the pattern of intracellular synthesis during cell cultivation. The identified divergent rRNAs could provide additional gene expression regulation in P. ginseng cells by forming heterogeneous ribosomes.

中文翻译：

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人参 CA Meyer 培养细胞系的 rDNA 簇中的年龄依赖性和组织特异性改变

长期种植人参细胞系导致传统医学中使用的生物活性物质的合成减少。为了深入了解可能影响这一过程的细胞机制，我们分析了东方人参细胞系 rDNA 簇内的变异。细胞系培养了 6 年和 24 年；分析了核仁和染色体的数量。克隆并测序了完整的 18S rDNA 序列。分析了序列的核苷酸多态性和系统发育关系，并对单独的 18S rRNA 区域的二级结构进行了建模。18S rDNA 在细胞培养过程中积累的突变与染色体和核仁数量的增加密切相关。核苷酸多样性的模式是文化特异性的，并且增加的多态性与胞嘧啶甲基化位点相关。一些 18S rRNA 区域的二级结构及其相互作用会在培养过程中发生变化。每个细胞系的系统发育树拓扑结构都是特定的。观察到的 rDNA 簇的改变与体细胞克隆变异有关，导致细胞培养过程中细胞内合成模式的变化。鉴定出的不同 rRNA 可以提供额外的基因表达调控 导致细胞培养过程中细胞内合成模式的变化。鉴定出的不同 rRNA 可以提供额外的基因表达调控 导致细胞培养过程中细胞内合成模式的变化。鉴定出的不同 rRNA 可以提供额外的基因表达调控P. ginseng细胞通过形成异质核糖体。