What is the specificity of plant subtelomeres?

Abstract

According to the current concept, formed through a comprehensive analysis of the molecular structure of human and yeast subtelomeres, these regions are particularly dynamic and variable parts of chromosomes enriched for segmental duplications. This chapter considers to what degree this concept is applicable to the subtelomeres of plant species with different genome sizes paying a special attention on the own results on the rye (Secale cereale) subtelomeric heterochromatin. The rye belongs to the species with a large genome size (8.3 × 109 bp). The S. cereale genome has increased during the evolution mostly through enlargement of the subtelomeric heterochromatic regions. The main components of this heterochromatin are a few multicopy tandemly repeated DNA families. Several arrays of each family localized to separate nonoverlapping domains have been detected in the short arm of the first rye chromosome. They display specific patterns of hierarchical arrangement into multimeric blocks, where the monomers form various higher-order repeat units. In conclusion, the data on a high rate of recombination characteristic of the plant subtelomeres are summarized. The consequence of these recombinations is various types of molecular rearrangements in these chromosomal regions, which contribute to the overall size of the genome.