Basis for high-affinity ethylene binding by the ethylene receptor ETR1 of Arabidopsis

Abstract

The gaseous hormone ethylene is perceived in plants by membrane-bound receptors, the best studied of these being ETR1 from Arabidopsis. Ethylene receptors can mediate a response to ethylene concentrations at less than one part per billion; however, the mechanistic basis for such high-affinity ligand binding has remained elusive. Here we identify an Asp residue within the ETR1 transmembrane domain that plays a critical role in ethylene binding. Site-directed mutation of the Asp to Asn results in a functional receptor that has a reduced affinity for ethylene, but still mediates ethylene responses in planta. The Asp residue is highly conserved among ethylene receptor-like proteins in plants and bacteria, but Asn variants exist, pointing to the physiological relevance of modulating ethylene-binding kinetics. Our results also support a bifunctional role for the Asp residue in forming a polar bridge to a conserved Lys residue in the receptor to mediate changes in signaling output. We propose a new structural model for the mechanism of ethylene binding and signal transduction, one with similarities to that found in a mammalian olfactory receptor.

Plant hormone ethylene: A leading edge in conferring drought stress tolerance

“…Ethylene signaling is a crucial mechanism to regulate plant growth and development. Most research on this mechanism has been conducted on Arabidopsis and transposed to study other plant species (Azhar et al, 2023). Ethylene receptors, including ETHYLENE RESPONSE1 (ETR1), ETR2, ETHYLENE RESPONSE SENSOR1 (ERS1), ERS2, and ETHYLENE INSENSITIVE4 (EIN4) are crucial for ethylene perception and signaling.…”

“…It can be concluded that ethylene modulated the activity of antioxidant enzymes for proper cellular functioning, thereby maintaining ROS and RNS metabolism under drought stress.3 | ROLE OF ETHYLENE SIGNALING COMPONENTS IN DROUGHT STRESS TOLERANCE3.1 | Ethylene signaling under drought stressEthylene signaling is a crucial mechanism to regulate plant growth and development. Most research on this mechanism has been conducted on Arabidopsis and transposed to study other plant species(Azhar et al, 2023). Ethylene receptors, including ETHYLENE RESPONSE1 (ETR1), ETR2, ETHYLENE RESPONSE SENSOR1 (ERS1), ERS2, and ETHYLENE INSENSITIVE4 (EIN4) are crucial for ethylene perception and signaling.…”

Ethylene, ACC, and the Plant Growth-Promoting Enzyme ACC Deaminase

“…According to the studies performed on A. thaliana , there are five ethylene receptors in this model plant that can be categorized into two clades, the first one containing ETR1 and ESR1 (Ethylene Response 1 and Ethylene Response Sensor 1, respectively) and the second represented by ETR2, ERS2, and EIN4 (Ethylene Response 2, Ethylene Response Sensor 2, and Ethylene Insensitive 4, respectively) [ 51 ]. A structural model of this ethylene receptor has been proposed by Schott-Verdugo et al [ 52 ] and, very recently, the structure of the ethylene-binding domain of ETR1 has been elucidated by Azhar et al [ 53 ]. Based on the fact that the functioning of the ethylene receptor is dependent on copper availability, it has been hypothesized that the whole mechanism of ethylene perception depends on an ancient copper transport mechanism that protects plant cells from the toxicity induced by high concentrations of this metal [ 54 ].…”

Beyond NPK: Mineral Nutrient-Mediated Modulation in Orchestrating Flowering Time

“…Arabidopsis heavy metal transporting ATPase 7 (HMA7)/RESPONSIVE TO ANTAGONIST 1 (RAN1), a P-type ATPase Cu transporter that is localized in the endomembrane reticulum (ER) of root and flower tissues, is required to deliver Cu to the ER-localizing ethylene receptors including Ethylene Response 1 (ETR1). The Cu binding to ETR1 is also needed for ethylene binding and functional receptors [ 228 , 229 , 230 , 231 , 232 , 233 ]. Two weak alleles of ran1 mutants ( ran1-1 and ran1-2 ) only show ethylene phenotypes upon the treatment of trans-cyclooctene, an ethylene-response antagonist, but not to ethylene, and the phenotype is suppressed by adding Cu ions [ 228 ].…”