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Abstract:
Immune responses that occur without an external trigger provide an effective platform for understanding the mechanisms underlying activation of immune signaling. In certain intra- and interspecific plant hybrids, autoimmunity can be triggered when immune system components meet that
have not been co-adapted. A particularly interesting case of hybrid necrosis in Arabidopsis thaliana is that of the RPP7 and RPW8 loci. RPP7, which confers race-specific resistance against oomycetes, encodes members of canonical coiled-coil, nucleotide-binding and leucine rich repeat
(CC-NLR) proteins. NLR proteins are the most common class of plant immune receptors. RPW8, which confers broad-spectrum resistance to biotrophic pathogens, belongs to the small family of RPW8/HR (Homologous to RPW8) coiled-coil-only domain proteins. Here, we will describe
the mechanisms by which the HR4Fei-0 and RPP7bLerik1-3 pair activates immune responses. Based on our findings, we propose a model that extends previous scenarios of NLR signaling based on ON/OFF equilibrium of closed, inactive and open, active NLR states.
