<Emphasis Type="Italic">Arabidopsis TTR1</Emphasis> causes LRR-dependent lethal systemic necrosis,rather than systemic acquired resistance,to Tobacco ringspot virus |
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Authors: | Moon Nam Serry Koh Sung Uk Kim Leslie L Domier Jae Heung Jeon Hong Gi Kim Su-Heon Lee Andrew F Bent Jae Sun Moon |
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Institution: | (1) Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai Osaka, 599-8531, Japan; |
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Abstract: | Most Arabidopsis ecotypes display tolerance to the Tobacco ringspot virus (TRSV), but a subset of Arabidopsis ecotypes, including Estland (Est), develop lethal systemic necrosis (LSN), which differs from the localized hypersensitive
responses (HRs) or systemic acquired resistance (SAR) characteristic of incompatible reactions. Neither viral replication
nor the systemic movement of TRSV was restricted in tolerant or sensitive Arabidopsis ecotypes; therefore, the LSN phenotype shown in the sensitive ecotypes might not be due to viral accumulation. In the present
study, we identified the Est TTR1 gene (tolerance to Tobacco ringspot virus 1) encoding a TIR-NBS-LRR protein that controls the ecotype-dependent tolerant/sensitive phenotypes by a map-based cloning
method. The tolerant Col-0 ecotype Arabidopsis transformed with the sensitive Est TTR1 allele developed an LSN phenotype upon TRSV infection, suggesting that the Est TTR1 allele is dominant over the tolerant ttr1 allele of Col-0. Multiple sequence alignments of 10 tolerant ecotypes from those of eight sensitive ecotypes showed that
10 LRR amino acid polymorphisms were consistently distributed across the TTR1/ttr1 alleles. Site-directed mutagenesis of these amino acids in the LRR region revealed that two sites, L956S and K1124Q, completely
abolished the LSN phenotype. VIGS study revealed that TTR1 is dependent on SGT1, rather than EDS1. The LSN phenotype by TTR1
was shown to be transferred to Nicotiana benthamiana, demonstrating functional conservation of TTR1 across plant families, which are involved in SGT-dependent defense responses,
rather than EDS1-dependent signaling pathways. |
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Keywords: | Arabidopsis lethal systemic necrosis TIR-NBS-LRR tobacco ringspot virus tolerance to tobacco ringspot virus 1 |
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