Transition metal-enhanced immunity in Arabidopsis roots via an NLR pair

Plants are challenged by multiple biotic (for example, pathogens) and abiotic (for example, heavy metals) stressors. Some transition metals can enhance a plant's defence against pathogens, but the mechanism remains unclear. Here we demonstrate that an Arabidopsis head-to-head gene pair of intracellular nucleotide-binding leucine-rich repeat (NLR) receptors, both expressed in the endodermis of roots, antagonistically control transition metal-enhanced immunity. One NLR, STM2, binds transition metal ions, such as Cd²⁺, Cu²⁺ and Zn²⁺, with its LRR domain to enhance its NAD⁺ hydrolytic activity and immune responses via the EDS1/PAD4/ADR1 module, triggering enhanced resistance to bacterial wilt Ralstonia solanacearum. The other NLR, STM1, suppresses STM2 to protect plants from transition metal-enhanced immunity and growth inhibition in the presence of excess metals. STM1 also dampens resistance to the pathogen. Our study defines an NLR activated by transition metals and reveals a trade-off between susceptibility to pathogens and sensitivity to transition metals that are pervasive in soil.