Functionally Homologous Host Components Recognize Potato Virus X in Gomphrena globosa and Potato.

Abstract

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 0. 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.

Activation of immune receptor Rx1 triggers distinct immune responses culminating in cell death after 4 hours

“…CP106, a CP derived from an avirulent PVX strain recognized by Rx1, was used to trigger Rx1‐mediated immune activation. CP105, a non‐Rx1‐recognized CP from a virulent virus, was used as a negative control (Goulden and Baulcombe, ; Jones et al ., ). The CP coding sequences were cloned in a DEX‐inducible expression vector.…”

Identification of Arabidopsis Mutants Exhibiting an Altered Hypersensitive Response in Gene-for-Gene Disease Resistance

“…Beneficial roles of the HR include the elimination of host cells that support pathogen growth, the release of antimicrobial compounds, and the release of signals that activate defense responses in neighboring and distant host cells. The HR is not always required for effective gene-for-gene resistance (Bendahmane et al 1999;Goulden and Baulcombe 1993;Lehnackers and Knogge 1990;Ori et al 1997;Schiffer et al 1997;Yu et al 1998). However, the above-noted benefits of HR cell death are apparently important in many gene-for-gene interactions, and useful information is expected from further study of the relationship between HR cell death and activation of host defenses.…”

Deciphering the transcriptional regulation and response of barley to obligate fungal biotroph invasion

“…The isolation of dnd (defense, no death) mutants in Arabidopsis found that resistance mediated by several R genes occurs without the generation of the HR (Yu et al, 1998). Similar results have been found in a variety of plant-pathogen interactions, including the interactions of Gomphrena globosa-potato virus X (PVX) (Goulden and Baulcombe, 1993), potato-PVX (Bendahmane et al, 1999), and oat-oat crown rust (Yu et al, 2001). Though it is not entirely clear if these events could be more broadly applicable to all plant-pathogen systems, it does raise the question to whether or not HR is (1) the direct phenotypic outcome of resistance or (2) an avoidable cell death.…”