Ethylene Receptors: Ethylene Perception and Signal Transduction
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Ethylene is sensed by a family of receptors that can be divided into two subfamilies based on phylogenetic analysis and some shared structural features. In this review we focus on the mechanistic aspects of how the receptors function in plants to transduce the ethylene signal. Recent work has led to new insights into how ethylene binds to the receptors and how this binding may induce a conformational change to regulate signaling. Additional studies point to several possible mechanisms for signal output by the receptors, which may involve changes in enzymatic activity and/or conformational changes. Other studies indicate the importance of interactions, both physical and genetic, between the receptors and early components of the signaling pathway, in particular, the Raf-like kinase CTR1, which functions as an integral component of the ethylene receptor signaling complex. The current model for signaling in Arabidopsis supports differing contributions from the receptors, with subfamily-1 receptors playing a more significant role than the subfamily-2 receptors in transmitting the ethylene signal.