Ethylene receptor (ETR (for family, with isoform abbreviations like ETR1, ERS1, ETR2, ERS2, EIN4 common in *Arabidopsis thaliana*))

Ethylene receptors are a family of plant transmembrane receptors that detect and transduce signals from the simple gaseous hormone **ethylene (C₂H₄)**, which regulates growth, development, and stress responses in plants. The best-studied examples are in *Arabidopsis thaliana*, where five homologs (ETR1, ERS1, ETR2, ERS2, EIN4) function as negative regulators of ethylene signaling. Structurally, each receptor contains a transmembrane domain that binds ethylene with copper as a cofactor, a GAF domain, a histidine kinase domain (sometimes degenerate), and, in some isoforms, a receiver domain. These receptors form dimers and higher-order complexes in the endoplasmic reticulum membrane, interacting with downstream components like the kinase CTR1 to control ethylene responses. Ethylene binding inactivates receptor signaling, relieving repression of ethylene-responsive genes and allowing plant processes like senescence, abscission, fruit ripening, and stress adaptation to proceed. These receptors are unique to plants and have no direct implication as therapeutic targets or disease associations in animals or humans.

Other names

Ethylene receptor familyEthylene gas receptorEthylene response sensor (ERS1)Ethylene-insensitive (EIN4)Ethylene-binding receptor

Ethylene binding leads to inactivation of the receptor’s signal repression, derepressing downstream ethylene-mediated responses. Receptors function as negative regulators in the absence of ethylene, actively repressing ethylene response via associated kinase activities.