Mechanical wounding of potato tubers induces replication of potato virus S

The replication of potato virus S in potato tuber tissue was induced by wounding. An acidic 32 kDa polypeptide accumulated in the polysome fraction of tubers upon wounding, concomitant with a transient increase in translational activity which is an integral component of the tuber wound response. We isolated and identified this polypeptide as the potato virus S coat protein. Immunoblot analyses indicated that the coat protein increased 2- to 20-fold in tubers within 4 h of wounding. Northern blot analyses showed a parallel increase in potato virus S genomic RNA during thr same time frame. Both potato virus S RNA and coat protein were barely detectable in tubers before wounding. By contrast, the significant amounts of coat protein detected in leaf and stem did not increase further upon wounding or treatment with abscisic acid or methyl jasmonate. The 32 kDa polypeptide was not detected in seed tubers certified as virus-free. The observation that potato virus X and potato virus Y were also induced 5- to 10-fold within 4 h of wounding led us to conclude that the induction of potato virus S in tubers resulted from the transient release from dormancy and general stimulation of tuber metabolism that occurs upon wounding. Wound-induction of potato virus S, potato virus X and potato virus Y may have implications on potato field practices or provide greater sensitivity in immunological screening of seed tubers for viruses. (C) 1996 Academic Press Limited