The Rx gene confers resistance to a range of Potexviruses in transgenic Nicotiana plants

INRA-URGV and University Evry Val d'Essonne, Evry, France.
Molecular Plant-Microbe Interactions (Impact Factor: 4.46). 10/2008; 21(9):1154-64. DOI: 10.1094/MPMI-21-9-1154
Source: PubMed

ABSTRACT 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.

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    • "Some of these resistant genes have been cloned and successfully transferred into existing elite cultivars of potato and other crop species. Up to date, transgenic plants have been obtained that are resistant to Potato virus X (PVX) in potato (van der Vossen et al., 2000), PVX in tobacco (Baurès et al., 2008), Narcissus mosaic virus (NMV) in tobacco (Baurès et al., 2008), White clover mosaic virus (WClMV) in tobacco (Baurès et al., 2008), Cymbidium mosaic virus (CymMV) in tobacco (Baurès et al., 2008), late blight in potato (Halterman et al., 2008), root cyst nematodes in potato (Paal et al., 2004; van der Vossen et al., 2000), cereal cyst nematodes in wheat (Vishnudasan et al., 2005), insect pests in rice (Bu et al., 2006; Rao et al., 2009) and fungi in rice (Quilis et al., 2007). Utilization of the resistant crops will enhance sustainable development of agriculture. "
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    • "Utilization of these pathogen-resistant cultivars increased yields significantly and improved the quality of potato production (Bradshaw and Bonierbale, 2010; Wang et al., 2011). Using genetic engineering approaches, disease-resistant genes were cloned from potato and successfully transferred into plant species such as potato (van der Vossen et al., 2000), tobacco (Baurès et al., 2008), wheat (Vishnudasan et al., 2005) and rice (Rao et al., 2009), and all of these transgenic plants showed resistance Table 2 Some examples of assessment of genetic and epigenetic integrity by molecular marker system in regenerants recovered from cryopreserved shoot tips. "
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    • "Similarly, NB-LRR genes show resistance to multiple viruses in the same genus. The N and Rx genes induce resistance to multiple members of the genus Tobamovirus and genus Potexvirus, respectively, whereas they have no effect on unrelated viruses (Tobias et al., 1982; Baurè s et al., 2008). This suggests that each gene responsible for virus resistance acts on a specific group of viruses, which enables plants to cover all of the innate immune responses to a vast diversity of viruses. "
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