SUMMARY. The intergenic spacer (IGS) of 5S ribosomal RNA genes (5S rDNA), which are present in the genome of all living organisms, is characterized by high variability, which makes it a convenient and widely used tool for studying issues of genome evolution, population genetics, systematics, etc. The objective of this study was to study the IGS of 5S rDNA of Antarctic pearlwort Colobanthus quitensis. Using molecular genetic methods, IGS region was amplified, cloned, and sequenced, followed by the analysis of structural organization. The IGS of 5S rDNA of C. quitensis was shown to contain basic regulatory elements typical of other vascular plants. At least two classes of 5S rDNA repeats, which differ significantly in length and nucleotide sequence of the spacer, were found in the individual genome. In addition, based on the differences in length and nucleotide sequence, 2 subclasses of the repeats with a long IGS and 3 subclasses of repeats with a short IGS were distinguished. Comparison of the sequences of the IGS of 5S rDNA of C. quitensis and Silene latifolia Poir., a species of another section of Caryophyllaceae, showed significant differences in the structure of the spacer of 5S rRNA genes, excluding its parts that contain regulatory elements. In general, the results indicate a significant level of intragenomic polymorphism of MGS 5S rDNA in C. quitensis.
Keywords: 5S rDNA, intergenic spacer, structural organization, variation, Colobanthus quitensis
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