Soybean NDR 1‐like proteins bind pathogen effectors and regulate resistance signaling

Summary Nonrace specific disease resistance 1 ( NDR 1) is a conserved downstream regulator of resistance (R) protein‐derived signaling. We identified two NDR 1‐like sequences ( G m NDR 1a, b) from soybean, and investigated their roles in R ‐ mediated resistance and pathogen effector detection. Silencing G m NDR 1a and b in soybean shows that these genes are required for resistance derived from the R pg1‐b , R pg3 , and R pg4 loci, against P seudomonas syringae ( P sg ) expressing avr B , avr B 2 and avr D 1 , respectively. Immunoprecipitation assays show that the G m NDR 1 proteins interact with the A vr B 2 and A vr D 1 P sg effectors. This correlates with the enhanced virulence of P sg avr B 2 and P sg avr D 1 in G m NDR 1‐silenced rpg3 rpg4 plants, even though these strains are not normally more virulent on plants lacking cognate R loci. The G m NDR 1 proteins interact with G m RIN 4 proteins, but not with A vr B , or its cognate R protein R pg1‐b. However, the G m NDR 1 proteins promote A vr B ‐independent activation of R pg1‐b when coexpressed with a phosphomimic derivative of G m RIN 4b. The role of G m NDR 1 proteins in R pg1‐b activation, their direct interactions with A vr B 2/ A vr D 1, and a putative role in the virulence activities of A vr effectors, provides the first experimental evidence in support of the proposed role for NDR 1 in transducing extracellular pathogen‐derived signals.