Plant “helper” immune receptors are Ca2+-permeable nonselective cation channels
Fangli Wu, M.R. Redinbo, F. El-Kasmi, Z.-M. Pei, K. Kempthorn, J.L. Dangl, O.J. Furzer, P. Jacob, N.H. Kim, Linlin Wan, W.G. Walton, A.D. Lietzan, S. Sunil, Y. Chi
Abstract
Plant nucleotide-binding leucine-rich repeat receptors (NLRs) regulate immunity and cell death. In Arabidopsis, a subfamily of “helper” NLRs is required by many “sensor” NLRs. Active NRG1.1 oligomerized, was enriched in plasma membrane puncta, and conferred cytoplasmic calcium ion (Ca2+) influx in plant and human cells. NRG1.1-dependent Ca2+ influx and cell death were sensitive to Ca2+ channel blockers and were suppressed by mutations affecting oligomerization or plasma membrane enrichment. Ca2+ influx and cell death mediated by NRG1.1 and ACTIVATED DISEASE RESISTANCE 1 (ADR1), another helper NLR, required conserved negatively charged N-terminal residues. Whole-cell voltage-clamp recordings demonstrated that Arabidopsis helper NLRs form Ca2+-permeable cation channels to directly regulate cytoplasmic Ca2+ levels and consequent cell death. Thus, helper NLRs transduce cell death signals directly.