title: Evidence for different, host-dependent functioning of Rx against both wild-type and recombinant Pepino mosaic virus.
abstract: The potato Rx gene provides resistance against Pepino mosaic virus (PepMV) in tomato; however, recent work has suggested that the resistance conferred may not be durable. Resistance breaking can probably be attributed to multiple mutations observed to accumulate in the capsid protein (CP) region of resistance-breaking isolates, but this has not been confirmed through directed manipulation of an infectious PepMV clone. The present work describes the introduction of two specific mutations, A-T78 and A-T114, into the coat protein minimal elicitor region of an Rx-controlled PepMV isolate of the EU genotype. Enzyme-linked immunosorbent assay (ELISA) and phenotypic evaluation were conducted in three Rx-expressing and wild-type solanaceous hosts: Nicotiana benthamiana, Nicotiana tabacum and Solanum lycopersicum. Mutation A-T78 alone was sufficient to confer Rx-breaking activity in N. benthamiana and S. lycopersicum, whereas mutation A-T114 was found to be associated, in most cases, with a secondary A-D100 mutation to break Rx-mediated resistance in S. lycopersicum. These results suggest that the need for a second, fitness-restoring mutation may be dependent on the PepMV mutant under consideration. Both mutations conferred Rx breaking in S. lycopersicum, whereas neither conferred Rx breaking in N. tabacum and only A-T78 allowed Rx breaking in N. benthamiana, suggesting that Rx may function in a different manner depending on the genetic background in which it is present.
authors: School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.
authors: Celia R A
authors: CR
authors: Duff-Farrier
authors: UMR 1332 Biologie du Fruit et Pathologie, INRA, CS 20032, 33882, Villenave d'Ornon Cedex, France.|UMR 1332 Biologie du Fruit et Pathologie, Université de Bordeaux, CS 20032, 33882, Villenave d'Ornon Cedex, France.
authors: Thierry
authors: T
authors: Candresse
authors: School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.
authors: Andy M
authors: AM
authors: Bailey
authors: The Food and Environment Research Agency, Sand Hutton, York, YO41 1LZ, UK.
authors: Neil
authors: N
authors: Boonham
authors: School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK.
authors: Gary D
authors: GD
authors: Foster
mesh_terms: D036022:Capsid Proteins / Q000378:metabolism; D016384:Consensus Sequence; D004797:Enzyme-Linked Immunosorbent Assay; D017343:Genes, Plant; D054884:Host-Pathogen Interactions; D018551:Solanum lycopersicum / Q000821:virology; D009029:Mosaic Viruses / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000821:virology; D011995:Recombination, Genetic / Q000235:genetics*; D014026:Nicotiana / Q000821:virology
chemical_list: D036022:Capsid Proteins
keywords: ELISA; Pepino mosaic virus; Rx gene; infectious clone; potexvirus; resistance breaking; site-directed mutagenesis