This study demonstrates that sequences homologous to those of the non-retro RNA virus (Potato virus Y; PVY) are integrated into the genome of several grapevine varieties. The integrated PVY-coat-protein-like cistron is expressed in the grapevine as indicated by Southern and Western blot analyses as well as by RNase protection assay. In addition, genome-walking studies showed that one PVY-like sequence is flanked by 41-bp direct repeats and is embedded in authentic grapevine sequences, flanked by inverted repeats. Rearranged PVY-like sequences were also found in tobacco. It is suggested that nonhomologous recombination of a potyviral RNA with RNA of a retrotransposable element took place at some point in evolution. The initial integration locus was probably within a grapevine gene homologous to a pentatricopeptide repeat-carrying protein, and was later transposed to other locations. The current location is reminiscent of a MITE-type retroelement, indicating transposition history. Because grapevine cultivars are propagated asexually, without going through a meiotic phase, the chance for DNA recombination is minimal and the foreign integrated sequence may be better conserved, enabling it to be expressed correctly in the recipient genome.
Amino Acid Sequence Base Sequence