CHARACTERIZATION OF A FAMILY OF TANDEMLY REPEATED DNA-SEQUENCES IN TRITICEAE

The recombinant plasmid dpTa1 has an insert of relic wheat DNA that re presents a family of tandemly organized DNA sequences with a monomeric length of approximately 340 bp. This insert was used to investigate t he structural organization of this element in the genomes of 58 specie s within the tribe Triticeae and in 7 species representing other tribe s of the Poaceae. The main characteristic of the genomic organization of dpTa1 is a classical ladder-type pattern which is typical for tande mly organized sequences. The dpTa1 sequence is present in all of the g enomes of the Triticeae species examined and in 1 species from a close ly related tribe (Bromus inermis, Bromeae). DNA from Hordelymus europa eus (Triticeae) did not hybridize under the standard conditions used i n this study. Prolonged exposure was necessary to obtain a weak signal . Our data suggest that the dpTa1 family is quite old in evolutionary terms, probably more ancient than the tribe Triticeae. The dpTa1 seque nce is more abundant in the D-genome of wheat than in other genomes in Triticeae. DNA from several species also have bands in addition to th e tandem repeats. The dpTa1 sequence contains short direct and inverte d subrepeats and is homologous to a tandemly repeated DNA sequence fro m Hordeum chilense.