Disease relevance of ETR1

• A sequence from the genome of the cyanobacterium Synechocystis sp. strain 6803 that shows homology to the ethylene-binding domain of ETR1 encodes a functional ethylene-binding protein [1].
• A truncated ETR1 receptor that lacks only the receiver domain restored normal growth to the triple mutant in air, but the transgenic seedlings displayed hypersensitivity to low doses of ethylene [2].
• Disease development in ethylene-insensitive Arabidopsis thaliana infected with virulent and avirulent Pseudomonas and Xanthomonas pathogens [3].
• The signal receiver domain of ETR1, an ethylene receptor from Arabidopsis thaliana, has been subcloned and expressed in E. coli and purified by affinity chromatography [4].

High impact information on ETR1

• Quadruple mutants had constitutive ethylene responses, revealing that these proteins negatively regulate ethylene responses and that the induction of ethylene response in Arabidopsis is through inactivation rather than activation of these proteins [5].
• Spatial patterns of expression of two immediate early auxin-responsive genes are altered in hookless1 mutants, suggesting that the ethylene response gene HOOKLESS1 controls differential cell growth by regulating auxin activity [6].
• CTR1, a negative regulator of the ethylene response pathway in Arabidopsis, encodes a member of the raf family of protein kinases [7].
• Mutations that eliminate ethylene binding to the receptor yield a dominant, ethylene-insensitive phenotype [8].
• Components of the ethylene signal transduction pathway have been identified by characterization of ethylene-response mutants in Arabidopsis thaliana [8].

Chemical compound and disease context of ETR1

• In contrast, the ethylene insensitive mutant etr1-1 exhibits glucose hypersensitivity [9].

Biological context of ETR1

• Chimeric transgene constructs in which the ETR1 promoter was used to drive expression of cDNAs for each of the five receptor isoforms were transferred into the ers1-2;etr1-7 double-mutant plants [10].
• Transformation of the ers1-2;etr1-7 double mutant with wild-type genomic ETR1 rescued the slow recovery phenotype, while a His kinase-inactivated ETR1 construct did not [11].
• Ethylene insensitivity is conferred by dominant mutations in the ETR1 gene early in the ethylene signal transduction pathway of Arabidopsis thaliana [12].
• The ETR1 gene was cloned by the method of chromosome walking [12].
• On the basis of sequence conservation between the Arabidopsis and the cyanobacterial ethylene-binding domains and on in vitro mutagenesis of ETR1, a structural model for this copper-based ethylene sensor domain is presented [1].

Anatomical context of ETR1

• Determinants within the amino-terminal half of ETR1 are sufficient for targeting to and retention at the endoplasmic reticulum [13].
• We report here that in both its native Arabidopsis and when transgenically expressed in yeast, the ETR1 protein is isolated from membranes as a dimer of 147 kDa [14].
• Evidence for a plastid origin of plant ethylene receptor genes [15].

Associations of ETR1 with chemical compounds

• Canonical histidine kinase activity of the transmitter domain of the ETR1 ethylene receptor from Arabidopsis is not required for signal transmission [10].
• It has been previously shown that a subfamily 1 Arabidopsis thaliana ethylene receptor, ETR1, autophosphorylates in vitro on a conserved histidine residue (1) [16].
• We analyzed the nature of the phosphorylated amino acids by acid/base stability and bi-dimensional thin layer electrophoresis and demonstrated that unlike ETR1 all other ethylene receptors autophosphorylate predominantly on serine residues [16].
• There was no significant impact on constitutive GS contents of blocking ET signaling (at ET resistant [etr1]) or reducing SA concentrations (nahG transgene) [17].
• Ethylene binding by ETR1 did not affect localization to the endoplasmic reticulum, based upon analysis of plants treated with the ethylene precursor 1-aminocyclopropane- 1-carboxylic acid and by examination of a mutant receptor that does not bind ethylene [13].

Physical interactions of ETR1

• Based on deletion analysis, the portion of CTR1 that interacts with ETR1 roughly aligns with the regulatory region of Raf kinases [18].
• Like AP2, ANT contains two AP2 domains homologous with the DNA binding domain of ethylene response element binding proteins [19].

Regulatory relationships of ETR1

• Additional investigations indicate that an ETR1-initiated phosphorelay regulates the transcription factor activity of ARR2 [20].
• OsEIL1, a rice homolog of the Arabidopsis EIN3 regulates the ethylene response as a positive component [21].
• In order to test the role of such factors in the ethylene signal transduction pathway during ripening, EIL1 fused to green fluorescent protein (GFP) has been over-expressed in the ethylene-insensitive non-ripening Nr mutant of tomato [22].
• Activation of the plant defensin gene PDF1.2 in Arabidopsis by pathogens has been shown previously to be blocked in the ethylene response mutant ein2-1 and the jasmonate response mutant coi1-1 [23].
• Expression of 35S:AtERF4-GFP in transgenic Arabidopsis plants conferred an ethylene-insensitive phenotype and repressed the expression of Basic Chitinase and beta-1,3-Glucanase, the GCC-box-containing genes [24].

Other interactions of ETR1

• EIN4 previously was isolated as a dominant ethylene-insensitive mutant [25].
• Sequence analysis showed that they are more closely related to ETR2 than they are to ETR1 or ERS1 [25].
• EIN4 and ERS2 are members of the putative ethylene receptor gene family in Arabidopsis [25].
• Thus, the data indicate that ethylene and H(2)O(2) signalling in guard cells are mediated by ETR1 via EIN2 and ARR2-dependent pathway(s), and identify AtrbohF as a key mediator of stomatal responses to ethylene [26].
• Thus, it is suggested that a signaling pathway independent for ETR1, JAR1 and NPR1 was operative to induce the resistance [27].

Analytical, diagnostic and therapeutic context of ETR1

• Although the sequence of the amino-terminal half of the deduced ETR1 protein appears to be novel, the carboxyl-terminal half is similar in sequence to both components of the prokaryotic family of signal transducers known as the two-component systems [12].
• By using the yeast two-hybrid assay, we detected a specific interaction between the CTR1 amino-terminal domain and the predicted histidine kinase domain of ETR1 and ERS [18].
• Site-directed mutagenesis of two cysteines near the amino terminus of ETR1 prevented formation of the covalently linked dimer in yeast, consistent with a role in disulfide bond formation [14].
• Examination by aqueous two-phase partitioning, sucrose density-gradient centrifugation, and immunoelectron microscopy indicates that ETR1 is predominantly localized to the endoplasmic reticulum [13].
• Genomic Southern blot analysis indicates that three or more ETR1 homologues exist in tomato [28].

References