Differential regulation of TNL‐mediated immune signaling by redundant helper CNLs

What is it about?

Nucleotide-binding leucine-rich repeat domain proteins (NLRs) are used by plants and animals as intracellular immune receptors to recognize pathogen-derived effectors and trigger a robust defense. In higher plants, the Activated Disease Resistance 1 (ADR1) family of coiled-coil NLRs (CNLs) have evolved as helper NLRs that function downstream of TIR-type sensor NLRs (TNLs). The NRG1 family of CNLs in Arabidopsis is closely related to ADR1s, but their function is unclear. Through CRISPR/Cas9 gene editing methods, we discovered that the tandemly repeated NRG1.1 and NRG1.2 are functionally redundant and operate downstream of TNLs with differential strengths. Synergistic effects on basal and TNL-mediated defense were detected among ADR1s and NRG1s. More importantly, NRG1s localize to the cytosol and endomembrane network regardless of the presence of effector, suggesting a cytosolic activation mechanism. Taken together, different sensor TNLs differentially use two groups of helper NLRs, ADR1s and NRG1s, to transduce downstream defense signals.

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