An rpw8 quadruple mutant of Arabidopsis Col-0 is partially compromised in bacterial and fungal resistance

Abstract

The plant immune system relies on both cellsurface and intracellular NLR (nucleotidebinding, leucine-rich repeat) receptors. NLRs respond to pathogen effectors and activate effector-triggered immunity: a cocktail of responses, often accompanied by cell death, resulting in resistance.

Atypical Resistance Protein RPW8/HR Triggers Oligomerization of the NLR Immune Receptor RPP7 and Autoimmunity

“…That the genetic requirements for RPP7 Col-0 signaling in Hpa resistance (McDowell et al, 2000) differ from the genetic requirements for HR4 Fei-0 /RPP7b autoimmunity (Figure 1D) suggests, however, that not all RPP7 homologs depend on RPW8/HR partners. This is also consistent with the observation that RPP7 Col-0 -mediated resistance to Hpa race Hiks1 does not require HR4 Col-0 (Barragan et al, 2019) and an rpw8 quadruple mutant in Col-0 is not obviously impaired in cell death responses after activation of certain NLRs (Castel et al, 2019b). There is precedence for closely related NLR proteins or even the same NLR protein associating with different ligands or responding to different effectors (Lewis et al, 2013;Seto et al, 2017;Wang et al, 2015).…”

Cavity surface residues of PAD4 and SAG101 contribute to EDS1 dimer signaling specificity in plant immunity

“…RPW8/HRs are small membrane‐binding proteins with a CC R ‐domain. Arabidopsis RPW8.1 and RPW8.2 promote EDS1 ‐ and PAD4 ‐dependent basal immunity to powdery mildew fungi and other pathogens (Berkey et al., 2017; Castel, Wu, et al., 2019; Xiao et al., 2001, 2004). Tested RPW8 and HR proteins accumulate at host membrane sites around fungal infection structures (haustoria) (Berkey et al., 2017; Wang et al., 2009).…”

Plant NLRs get by with a little help from their friends

“…Furthermore, RNL-dependent NLRs such as RRS1/RPS4, RPS2 and WRR4A do not require RPW8 to signal [45]. Nevertheless, the rpw8 mutant is slightly impaired in resistance to adapted and non-adapted strains of powdery mildew, and to Pseudomonas syringae pv tomato strain DC3000 [45]. Thus, RPW8 likely plays a role in plant immunity distinct from RNL helpers.…”

“…Structural information about RPW8 and an RNL N-terminus, though not available to date, would shed light on this question. The resemblance between RPW8 and the RPW8 domain of RNLs suggests that RPW8 might be involved in RNL signaling, however, an Arabidopsis rpw8 mutant does not phenocopy an nrg1 mutant [45]. Furthermore, RNL-dependent NLRs such as RRS1/RPS4, RPS2 and WRR4A do not require RPW8 to signal [45].…”

“…The resemblance between RPW8 and the RPW8 domain of RNLs suggests that RPW8 might be involved in RNL signaling, however, an Arabidopsis rpw8 mutant does not phenocopy an nrg1 mutant [45]. Furthermore, RNL-dependent NLRs such as RRS1/RPS4, RPS2 and WRR4A do not require RPW8 to signal [45]. Nevertheless, the rpw8 mutant is slightly impaired in resistance to adapted and non-adapted strains of powdery mildew, and to Pseudomonas syringae pv tomato strain DC3000 [45].…”