MOLECULAR CHARACTERIZATION OF A TANDEM REPEAT, AFA FAMILY, AND DISTRIBUTION AMONG TRITICEAE

We have characterized a so-called D genome specific repetitive DNA seq uence (pAsl) of Aegilops squarrosa L. (2n = 14, genome DD) with respec t to its DNA sequence and its distribution among Triticeae species. Th e clone consisted of three units of a repetitive DNA sequence of 336 o r 337 base pairs, and was AT rich (65.2%). DNA analyses revealed the p resence of the pAsl-like sequences in other genomes of Triticeae speci es, although the repetition was greatly (as much as 100-fold) variable among the genomes. The repetitive sequences from 10 diploid species w ere amplified using PCR with specific primers, and the sequential vari ability was analyzed by the digestion pattern obtained with five restr iction enzymes. Since the AfaI site was the most conservatively presen t in the unit of the repetitive sequences, we named them ''Afa family. '' The analysis clearly displayed the variation of the repetitive sequ ences regardless of the uniformity of the size of the amplified produc t. These results indicated that plural amplification events of these r epetitive sequences happened independently in the genome evolution of Triticeae.