Ethylene receptors are functionally conserved in calcium permeability across the green lineage

ABSTRACT The gaseous hormone ethylene plays a key role in regulating plant growth and stress responses. Although Ca²⁺ has long been implicated in ethylene signaling, the identity of molecules controlling Ca²⁺ permeability involved has remained elusive. Here we show that Arabidopsis ethylene receptors ETR1 and ERS1 are Ca 2+ permeable, and that ETR1 mediates ethylene-induced cytosolic Ca 2+ increase and regulates hypocotyl elongation. Homologs of ETR1 from eight land plant and algal species also exhibit Ca²⁺ permeability, suggesting an evolutionarily conserved function. We further demonstrate ethylene enhances the Ca 2+ permeability of ETR1 and its homologue from the charophyte Klebsormidium flaccidum . These findings uncover a previously unrecognized but conserved role of ethylene receptors in Ca²⁺ permeability regulation in the green lineage, with broad implications for Ca²⁺ signaling in plant development and environmental adaptation.