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 Ca 2+ 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 cngc11 / 12 mutants exhibited hypersensitivity to Mn and cngc12 mutant showed reduced Ca 2+ elevations. The brassinosteroid (BR) receptor BRI1 physically interacted with CNGC12 and phosphorylated Ser22 residue, a modification critical for channel activation. Accordingly, bri1 mutants displayed impaired Mn-induced Ca 2+ 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 Ca 2+ currents. Exogenous brassinolide treatment augmented high-Mn-induced Ca 2+ 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 Ca 2+ -dependent Mn detoxification, revealing how phytohormone pathways regulate ion stress adaptation.