Variations of two repetitive DNA sequences in several Triticeae genomes revealed by polymerase chain reaction and sequencing.

Genomes of Triticeae were analyzed using PCR with synthesized primers that were based on two published repetitive DNA sequences, pLeUCD2 (pLe2) and 1-E6hcII-1 (L02368),which were originally isolated from Thinopyrum elongatum. The various genomes produced a 2240 bp PCR product having high homology with the repetitive DNA pLe2. The PCR fragments produced from different genomes differed mainly in amplification quantity and in base composition at 89 variable sites. On the other hand, amplification products from the primer set for L02368 were of different sizes and nucleotide sequences. These results show that the two repetitive DNA sequences have different evolutionary significance. ple2 is present in all genomes tested, although differences in copy number and nucleotide sequence are notable. L02368 is more genome specific, i.e., fewer genomes possess this family of repetitive sequences. It was concluded that the repetitive sequence pLe2 family is an ancient one that existed in progenitor genome prior to divergence of annual and perennial genomes. In contrast, sequences similar to L02368 have only evolved following genome divergence.