Ethylene‐binding activity, gene expression levels, and receptor system output for ethylene receptor family members from Arabidopsis and tomato^†

Abstract

SummaryEthylene signaling in plants is mediated by a family of ethylene receptors related to bacterial two-component regulators. Expression in yeast of ethylene-binding domains from the five receptor isoforms from Arabidopsis thaliana and five-receptor isoforms from tomato confirmed that all members of the family are capable of highaffinity ethylene-binding activity. All receptor isoforms displayed a similar level of ethylene binding on a per unit protein basis, while members of both subfamily I and subfamily II from Arabidopsis showed similar slowrelease kinetics for ethylene. Quantification of receptor-isoform mRNA levels in receptor-deficient Arabidopsis lines indicated a direct correlation between total message level and total ethylene-binding activity in planta. Increased expression of remaining receptor isoforms in receptor-deficient lines tended to compensate for missing receptors at the level of mRNA expression and ethylene-binding activity, but not at the level of receptor signaling, consistent with specialized roles for family members in receptor signal output.

Ethylene Receptor 1 (ETR1) Is Sufficient and Has the Predominant Role in Mediating Inhibition of Ethylene Responses by Silver in Arabidopsis thaliana

“…We used the following nomenclature for these constructs: -GST for the binding domains of ETR1, ETR2, ERS1, ERS2, and EIN4 respectively fused to GST (15). These constructs were described and characterized previously using Saccharomyces cerevisiae as the expression system (15,32).…”

“…In some cases empty vector controls were included. The time-course of ethylene dissociation from ETR1[1-128]-GST and the K d for ethylene binding to ETR1 -GST were determined according to methods from prior studies (15,41,52).…”

“…This requirement for copper is likely to be a general feature of all ethylene receptors in plants (15). Additionally, prior studies indicate that RAN1 (response to antagonist 1) is a copper transporter that acts upstream of the receptors and is required for normal biogenesis of the receptors (37)(38)(39)(40).…”

The Copper Transporter RAN1 Is Essential for Biogenesis of Ethylene Receptors in Arabidopsis

“…Interestingly, the etr1-1 mutant fails to coordinate copper and is unable to bind ethylene (16,19). This requirement for copper is likely to be a general feature of all ethylene receptors in plants (17).…”

Modulation of Ethylene Responses Affects Plant Salt-Stress Responses

“…Subfamily II includes ETR2, EIN4, and ERS2 Sakai et al, 1998). All these ethylene receptors can bind ethylene, and ETR1 has His kinase activity (Schaller and Bleecker, 1995;Gamble et al, 1998;Hall et al, 2000;O'Malley et al, 2005). Other Arabidopsis ethylene receptors had Ser kinase activity (Moussatche and Klee, 2004).…”