Identification of a Chloroplastic "RNA Tractor" within the Genome of Potato Virus X (PVX)

Previous studies have detected the presence of the capsid protein (CP) and CP RNA of PVX in chloroplasts of transgenic plants expressing the PVX CP and 8kD genes from nuclear transgenes. CP RNA was also found in the chloroplasts of transgenic plants with mutations that eliminated either the CP or the 8kD protein. To further investigate the potential “RNA Tractor” activity of the PVX RNA, various constructs containing limited regions of the PVX 8kD and CP genes were produced and used to transform tobacco plants. RT-PCR analyses of chloroplastic RNA ascertained the presence of the RNA transcript within chloroplasts when as little as 125bp of the PVX sequence was used to transform plants. From this, it was concluded that the PVX proteins did not contribute to the movement of the viral RNA and that a region within the 125bp PVX sequence is acting as a chloroplastic “RNA Tractor”.MAS