Yali Zhu,^1,2 Larry Green,¹ Young-Min Woo,¹ Robert Owens,⁴ and Biao Ding,^1,2

¹ Department of Botany, Oklahoma State University, Stillwater

² Department of Plant Biology, Ohio State University, Columbus

⁴ Molecular Plant Pathology Laboratory, Agricultural Research Services, United States Department of Agriculture, Beltsville, Maryland

Viroids are small, non-translatable pathogenic RNAs that replicate autonomously and traffic systemically in their host plants. We have used in situ hybridization to analyze the trafficking pattern of Potato spindle tuber viroid (PSTVd) in tomato and Nicotiana benthamiana. When PSTVd was inoculated onto the stem of a plant, it replicated and trafficked to sink, but not source, leaves. PSTVd was absent from shoot apical meristems. In the flowers of infected plants, PSTVd was present in the sepals, but was absent in the petals, stamens, and ovary. The replicative form of PSTVd was detected in the phloem. Our data demonstrate that (i) PSTVd traffics long distance in the phloem and this trafficking is likely sustained by replication of the viroid in the phloem, and (ii) PSTVd trafficking is governed by plant developmental and cellular factors. The dependency of PSTVd and other viroids on cellular mechanisms for RNA trafficking makes them excellent tools to study such mechanisms.

References

Zhu, Y., Green, L., Woo, Y.-M., Owens, R., and Ding, B. (2000). Cellular basis of potato spindle tuber viroid systemic movement. Virology (In press).

Ding, B., Itaya, A., and Woo, Y.-M. (1999). Plasmodesmata and cell-to-cell communication in plants. Internatl. Rev. Cytol. 190:251-316.

Woo, Y.-M., Itaya, A., Owens, R.A., Tang, L., Hammond, R.W., Chou, H.-C., Lai, M.M.C., and Ding, B. (1999). Characterization of nuclear import of potato spindle tuber viroid RNA in permeabilized protoplasts. Plant J. 17:627-635.

Ding, B., Kwon, M.-O., Hammond, R. and Owens, R. (1997). Cell-to-cell movement of potato spindle tuber viroid. Plant J. 12:931-936.