Plant highly repeated satellite DNA: molecular evolution, distribution and use for identification of hybrids

Relationships among genomes are often revealed by the occurrence of common or related satellite DNA (satDNA) types. A typical satDNA characterized by specific sites for one (or more) restriction endonuclease(s) is called 'restriction satellite DNA'. Restriction satDNA comprises - in addition to transposons and retrotransposable elements - often highly repeated genome components present in most higher plants. Large arrays of satDNA elements are concentrated at subtelomeric and/or centromeric regions (intermingled with other retrotransposon-derived elements), however, they can be also located as large intercalating blocks along the chromosome. The head-to-tail tandemly arranged repeat units (monomers) of satDNA mostly exhibit lengths of 160 to 180 bp or 320 to 370 bp, but other lengths were also found in plants. In particular, in interspecific hybrids between more distantly related species, which often exist only after polyploidization, the individual repetitive DNA of the crossing partners contribute to recombination and rearrangement processes in the hybrids, thereby stimulating genome evolution. Here, we concentrate on the possible origin, molecular evolution, organization and distribution of highly repeated satDNA in various higher plants with emphasis on hybrids and allopolyploids.