PARACENTROMERIC SEQUENCES ON TOMATO CHROMOSOME-6 SHOW HOMOLOGY TO HUMAN SATELLITE-III AND TO THE MAMMALIAN CENP-B BINDING BOX

In order to isolate centromeric sequences from tomato (Lycopersicon es culentum) chromosome 6, a large-scale RAPD screen was performed. Among 1500 polymorphic RAPD markers tested, 100 were identified as chromoso me 6-specific, using a L. esculentum substitution line carrying chromo some 6 from L. pennellii. Fifty-seven of these markers proved to origi nate from L. pennellii, and of these, 13 were genetically mapped betwe en the morphological markers yellow virescent (yv) and thiaminless (tl ), which flank the centromere. These markers could be assigned to thre e genetic loci, with 11 of the markers mapping to a single locus. Furt her resolution of this cluster was achieved using radiation-induced de letions that removed vv or tl but not the centromere. Seven markers we re shown to be located outside all of the deletions. These seven marke rs and three of the other markers of the cluster were cloned and seque nced. Five of the clones are present as single-copy or low-copy-number sequences and five represent middle repetitive sequences. Three seque nces show homology to the mammalian CENP-B binding box clone AG12 cont ains two of these boxes and also shows homology to human satellite III .