A BRI1-CNGC12 phosphorylation module links hormone signaling to manganese homeostasis in plants.

Abstract

Manganese (Mn) toxicity in acidic or waterlogged soils severely impacts crop productivity. Although high-Mn stress triggers Ca²⁺ signals that regulate Mn homeostasis, the mechanism generating these signals remains unclear. Here, we show that the cyclic nucleotide-gated channel CNGC11/12 are essential for Mn tolerance, as <i>cngc11</i>/<i>12</i> mutants exhibited hypersensitivity to Mn and <i>cngc12</i> mutant showed reduced Ca²⁺ elevations. The brassinosteroid (BR) receptor BRI1 physically interacted with CNGC12 and phosphorylated Ser22 residue, a modification critical for channel activation. Accordingly, <i>bri1</i> mutants displayed impaired Mn-induced Ca²⁺ signaling and heightened Mn sensitivity. Mn stress rapidly activated BRI1 kinase, peaking within minutes, and electrophysiological assays confirmed that BRI1-mediated phosphorylation gates CNGC12-dependent Ca²⁺ currents. Exogenous brassinolide treatment augmented high-Mn-induced Ca²⁺ signaling, BRI1-mediated CNGC12 phosphorylation, and high-Mn tolerance. Mutations in either BRI1 or CNGC12 abolished CPK5-dependent phosphorylation of MTP8 and impaired NRAMP1 endocytosis. Our study identifies the BRI1-CNGC12 module as a key node linking BR signaling to Ca²⁺-dependent Mn detoxification, revealing how phytohormone pathways regulate ion stress adaptation.