Plant “nucleotide-binding leucine-rich repeat” receptor proteins (NLRs) detect alterations in host targets of pathogen effectors and trigger immune responses. The Arabidopsis thaliana
mutant pen1 syp122
displays autoimmunity, and a mutant screen identified the deubiquitinase “associated molecule with the SH3 domain of STAM3” (AMSH3) to be required for this phenotype. AMSH3 has previously been implicated in ESCRT-mediated vacuolar targeting. Pathology experiments show that AMSH3 activity is required for immunity mediated by the CC-NLRs, RPS2 and RPM1. Co-expressing the autoactive RPM1D505V
and the catalytically inactive ESCRT-III protein SKD1E232Q
in Nicotiana benthamiana
supports the requirement of ESCRT-associated functions for this CC-NLR-activated immunity. Meanwhile, loss of ESCRT function in A. thaliana
is lethal, and we find that AMSH3 knockout-triggered seedling lethality is “enhanced disease susceptibility 1” (EDS1) dependent. Future studies may reveal whether AMSH3 is monitored by a TIR-NLR immunity receptor.