THE PLANT CELL, Vol 5, Issue 8 921-930, Copyright © 1993 by American Society of Plant Biologists
Functionally Homologous Host Components Recognize Potato Virus X in Gomphrena globosa and Potato
M. G. Goulden and D. C. Baulcombe
The Sainsbury Laboratory, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom
All known isolates of potato virus X (PVX), with the exception of a South
American isolate PVXHB, induce an extreme resistance response on potato
carrying the Rx gene and elicit the production of necrotic lesions on
Gomphrena globosa: PVXHB establishes systemic infection on Rx genotypes of
potato and infects the inoculated leaf of G. globosa without lesion
formation. Previously, we have shown that the Rx-mediated resistance is
affected by a feature of the coat protein that depends on the presence of a
threonine residue at position 121 in the coat protein of PVXCP4 and that
the resistance is an induced response expressed in protoplasts of potato
with the Rx genotype. In this study, we provide evidence, based on the
analysis of PVXCP4/PVXHB hybrids, that the elicitation of lesions on G.
globosa also requires the presence of a threonine residue at position 121
of the viral coat protein. The lesion-forming phenotype was not associated
with the ability of the viral isolate to accumulate in the infected plant.
We therefore propose that there is a homologous component of both potato
carrying Rx and G. globosa that interacts with a feature of the PVX coat
protein and, following the interaction, activates an induced response in
the plant cell.
