Arabidopsis SENESCENCE-ASSOCIATED GENE101 stabilizes and signals within an ENHANCED DISEASE SUSCEPTIBILITY1 complex in plant innate immunity.

Plant innate immunity against invasive biotrophic pathogens depends on the intracellular defense regulator ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). We show here that Arabidopsis thaliana EDS1 interacts in vivo with another protein, SENESCENCE-ASSOCIATED GENE101 (SAG101), discovered through a proteomic approach to identify new EDS1 pathway components. Together with PHYTOALEXIN-DEFICIENT4 (PAD4), a known EDS1 interactor, SAG101 contributes intrinsic and indispensable signaling activity to EDS1-dependent resistance.

Arabidopsis RAR1 exerts rate-limiting control of R gene-mediated defenses against multiple pathogens.

We have identified the Arabidopsis ortholog of barley RAR1 as a component of resistance specified by multiple nucleotide binding/Leu-rich repeat resistance (R) genes recognizing different bacterial and oomycete pathogen isolates. Characterization of partially and fully defective rar1 mutations revealed that wild-type RAR1 acts as a rate-limiting regulator of early R gene-triggered defenses, determining the extent of pathogen containment, hypersensitive plant cell death, and an oxidative burst at primary infection sites. We conclude that RAR1 defense signaling function is conserved between plant species that are separated evolutionarily by 150 million years.