Ty1-copia group retrotransposons as ubiquitous components of plant genomes.

Ty1-copia group retrotransposons were searched for in 35 plant species by amplification of the reverse transcriptase coding region using the polymerase chain reaction. Sequences of the expected size were amplified from all of these plant species, including a liverwort, a horsetail, a bracken, gymnosperms and angiosperms. Sequences of 72 clones from 17 species were determined, all of which showed clear homology to the reverse transcriptase sequence of Ty1-copia type retrotransposons. More than half of the sequences carried stop codons or frame shifts. Twenty three new retrotransposon sequences with no interruption by these mutations were revealed. The mechanisms of the evolution of retrotransposons and accumulation of mutations were discussed.