Tnr8, a foldback transposable element from rice

Abstract

An insertion sequence 418 bp in length was found in one member of rice retroposon p-SINE1 in Oryza glaberrima. This sequence had long terminal inverted repeats (TIRs) and is flanked by direct repeats of a 9-bp sequence at the target site, indicative that the insertion sequence is a rice transposable element, which we named Tnr8. Interestingly, each TIR sequence consisted of a unique 9-bp terminal sequence and six tandem repeats of a sequence about 30 bp in length, like the foldback transposable element first identified in Drosophila. A homology search of databases and analysis by PCR revealed that a large number of Tnr8 members with sequence variations were present in the rice genome. Some of these members were not present at given loci in several rice species with the AA genome. These findings suggest that the Tnr8 family members transposed long ago, but some appear to have mobilized after rice strains with the AA genome diverged. The Tnr8 members are thought to be involved in rearrangements of the rice genome.