Ethylene receptors at the ER: Potential hubs integrating hormone, redox, and Ca 2+ signaling

ABSTRACT Arabidopsis thaliana Ethylene Response 1 (ETR1) has long been viewed as a canonical hormone receptor initiating ethylene signaling at the endoplasmic reticulum (ER). Recent studies demonstrate that ETR1 also acts as an ER redox sensor, with disulfide‐dependent dimerization controlling receptor conformation and activity. In parallel, subfamily I ethylene receptors, including ETR1, function as Ca 2+ ‐permeable channels, directly linking ethylene perception to rapid cytosolic Ca 2+ elevation. Here, we summarize emerging evidence that redefines ETR1 as a multifunctional signaling hub connecting ethylene perception, redox regulation, and Ca 2+ signaling. We present this integration as a working model and highlight unresolved questions concerning the mechanistic relationships among these functions. This framework provides a new perspective on how plants integrate ER homeostasis with hormone signaling to coordinate development and stress adaptation.