A NOVEL SPECIES-SPECIFIC TANDEM REPEAT DNA FAMILY FROM SINAPIS-ARVENSIS - DETECTION OF TELOMERE-LIKE SEQUENCES

DNA sequences representing a tandemly repeated DNA family of the Sinap is arvensis genome were cloned and characterized. The 700-bp tandem re peat family is represented by two clones, pSA35 and pSA52, which are 6 97 and 709 bp in length, respectively. Dot matrix analysis of the sequ ences indicates the presence of repeated elements within each monomeri c unit. Sequence analysis of the repetitive region of clones pSA35 and pSA52 shows that there are several copies of a 7-bp repeat element or ganized in tandem. The consensus sequence of this repeat element is 5' -TTTAGGG-3'. These elements are highly mutated and the difference in l ength between the two clones is due to different copy numbers of these elements. The repetitive region of clone DSA35 has 26 copies of the e lement TTTAGGG, whereas clone pSA52 has 28 copies. The repetitive regi on in both clones is flanked on either side by inverted repeats that m ay be footprints of a transposition event. Sequence comparison indicat es that the element TTTAGGG-is identical to telomeric repeats present in Arabidopsis, maize, tomato, and other plants. However, Bal31 digest ion kinetics indicates non-telomeric localization of the 700-bp tandem repeats. The clones represent a novel repeat family as (i) they conta in telomere-like motifs as subrepeats within each unit, and (ii) they do not hybridize to related crucifers and are species-specific in natu re.