Diverse NLR immune receptors activate defence via the RPW 8‐ NLR NRG 1

Summary Most land plant genomes carry genes that encode RPW 8‐ NLR Resistance (R) proteins. Angiosperms carry two RPW 8‐ NLR subclasses: ADR 1 and NRG 1. ADR 1s act as ‘helper’ NLR s for multiple TIR ‐ and CC ‐ NLR R proteins in Arabidopsis. In angiosperm families, NRG 1 co‐occurs with TIR ‐ NLR Resistance ( R ) genes. We tested whether NRG 1 is required for signalling of multiple TIR ‐ NLR s. Using CRISPR mutagenesis, we obtained an nrg1a‐nrg1b double mutant in two Arabidopsis accessions, and an nrg1 mutant in Nicotiana benthamiana . These mutants are compromised in signalling of all TIR ‐ NLR s tested, including WRR 4A, WRR 4B, RPP 1, RPP 2, RPP 4 and the pairs RRS 1/ RPS 4, RRS 1B/ RPS 4B, CHS 1/ SOC 3 and CHS 3/ CSA 1. In Arabidopsis, NRG 1 is required for the hypersensitive cell death response ( HR ) and full oomycete resistance, but not for salicylic acid induction or bacterial resistance. By contrast, nrg1 loss of function does not compromise the CC ‐ NLR R proteins RPS 5 and MLA . RPM 1 and RPS 2 ( CC ‐ NLR s) function is slightly compromised in an nrg1 mutant. Thus, NRG 1 is required for full TIR ‐ NLR function and contributes to the signalling of some CC ‐ NLR s. Some NRG 1‐dependent R proteins also signal partially via the NRG 1 sister clade, ADR 1. We propose that some NLR s signal via NRG 1 only, some via ADR 1 only and some via both or neither.