The abundance of various polymorphic microsatellite motifs differs between plants and vertebrates.

The abundance of different simple sequence motifs in plants was accessed through data base searches of DNA sequences and quantitative hybridization with synthetic dinucleotide repeats. Database searches indicated that microsatellites are five times less abundant in the genomes of plants than in mammals. The most common plant repeat motif was AA/TT followed by AT/TA and CT/GA. This group comprised about 75% of all microsatellites with a length of more than 6 repeats. The GT/CA motif being the most abundant dinucleotide repeat in mammals was found to be considerably less frequent in plants. To address the question if plant simple repeat sequences are variable as in mammals, (GT)n and (CT)n microsatellites were isolated from B.napus. Five loci were investigated by PCR-analysis and amplified products were obtained for all microsatellites from B. oleracea, B.napus and B.rapa DNA, but only for one primer pair from B.nigra. Polymorphism was detected for all microsatellites.