The nucleotide sequence of a cloned RAPD DNA marker (OPI08) linked to a disease resistance gene in L. sativa (lettuce) revealed homology with the conserved domain of the reverse transcriptase of Ty3/gypsy retrotransposons. To further characterize the presence of Ty3/gypsy-like sequences in plants, sets of degenerate primers deduced from archetype retrotransposons were used for PCR amplification of a sequence domain characteristic of the reverse transcriptase and the integrase of Ty3/gypsy retrotransposons. The nucleotide sequence of two cloned DNA fragments of Z. mays (maize) and A. thaliana proved to be homologous with the conserved domains of the reverse transcriptase and the integrase of Ty3/gypsy retrotransposons. Southern blot analysis also demonstrated homology of the Z. mays clone to Lycopersicon (tomato) and L. sativa. This is the first report of Ty3/gypsy-like sequences in A. thaliana, and L. sativa. This research brings to six the number of plant species where this type of element has been reported, in contrast to the large number of plant Ty1/copia transposable elements described. It is not known whether these elements are actively transposing in plant genomes.

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