title: Histidine kinase activity of the ethylene receptor ETR1 facilitates the ethylene response in Arabidopsis.
abstract: In Arabidopsis (Arabidopsis thaliana), ethylene is perceived by a receptor family consisting of five members. Subfamily 1 members ETHYLENE RESPONSE1 (ETR1) and ETHYLENE RESPONSE SENSOR1 (ERS1) have histidine kinase activity, unlike the subfamily 2 members ETR2, ERS2, and ETHYLENE INSENSITIVE4 (EIN4), which lack amino acid residues critical for this enzymatic activity. To resolve the role of histidine kinase activity in signaling by the receptors, we transformed an etr1-9;ers1-3 double mutant with wild-type and kinase-inactive versions of the receptor ETR1. Both wild-type and kinase-inactive ETR1 rescue the constitutive ethylene-response phenotype of etr1-9;ers1-3, restoring normal growth to the mutant in air. However, the lines carrying kinase-inactive ETR1 exhibit reduced sensitivity to ethylene based on several growth response assays. Microarray and real-time polymerase chain reaction analyses of gene expression support a role for histidine kinase activity in eliciting the ethylene response. In addition, protein levels of the Raf-like kinase CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), which physically associates with the ethylene receptor ETR1, are less responsive to ethylene in lines containing kinase-inactive ETR1. These data indicate that the histidine kinase activity of ETR1 is not required for but plays a modulating role in the regulation of ethylene responses. Models for how enzymatic and nonenzymatic regulation may facilitate signaling from the ethylene receptors are discussed.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: Brenda P
authors.initials: BP
authors.lastname: Hall
authors.forename: Samina N
authors.initials: SN
authors.lastname: Shakeel
authors.forename: Madiha
authors.initials: M
authors.lastname: Amir
authors.forename: Noor
authors.initials: N
authors.lastname: Ul Haq
authors.forename: Xiang
authors.initials: X
authors.lastname: Qu
authors.forename: G Eric
authors.initials: GE
authors.lastname: Schaller
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D005030:Ethylenes / Q000378:metabolism / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D000071677:Histidine Kinase; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction; D014170:Transformation, Genetic
chemical_list: D029681:Arabidopsis Proteins; C494590:ETR1 protein, Arabidopsis; D005030:Ethylenes; D011956:Receptors, Cell Surface; C036216:ethylene; D011494:Protein Kinases; C477753:CTR1 protein, Arabidopsis; D000071677:Histidine Kinase