The Rx gene confers resistance to a range of potexviruses in transgenic Nicotiana plants.
Rx-mediated resistance was analyzed in Rx-expressing transgenic Nicotiana plants. The infection outcome of nine Potato virus X isolates mutated at amino acid positions 121 and 127 of the coat protein (CP) confirmed the key role of these amino acids but provided a more complex picture than previously reported. In particular, in Rx-expressing Nicotiana spp., eliciting activity modulated by amino acid 121 was conditioned by the nature of amino acid 127. These results suggest that the specificity of recognition might be modulated by host factors that are somehow subtly modified between Rx-expressing potato and Rx-expressing transgenic Nicotiana plants. Moreover, the CP of three Potexviruses, Narcissus mosaic virus (NMV), White clover mosaic virus (WClMV), and Cymbidium mosaic virus (CymMV), are all recognized by the Rx-based machinery and able to trigger an Rx-dependant hypersensitive response. A smaller elicitor of 90 amino acids was identified in the CP of NMV and WClMV, which contains the previously identified key positions 121 and 127. This elicitor is only weakly conserved (approximately 40% identity) among the CP of the various recognized viruses, suggesting that the Rx molecular machinery targets a conserved structural element of the Potexvirus CP rather than a conserved amino acid motif.
Baurès
Isabelle
I
INRA-URGV and University Evry Val d'Essonne, Evry, France.
Candresse
Thierry
T
Leveau
Aymeric
A
Bendahmane
Abdelhafid
A
Sturbois
Bénédicte
B
D000595:Amino Acid Sequence; D015153:Blotting, Western; D036022:Capsid Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D018515:Plant Leaves / Q000235:genetics / Q000821:virology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics* / Q000821:virology; D017863:Potexvirus / Q000235:genetics* / Q000254:growth & development; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics* / Q000821:virology
D036022:Capsid Proteins; D010940:Plant Proteins; C120017:Rx protein, Solanum tuberosum