title: Regulation of ethylene gas biosynthesis by the Arabidopsis ETO1 protein.
abstract: Ethylene gas is used as a hormone by plants, in which it acts as a critical growth regulator. Its synthesis is also rapidly evoked in response to a variety of biotic and abiotic stresses. The Arabidopsis ethylene-overproducer mutants eto2 and eto3 have previously been identified as having mutations in two genes, ACS5 and ACS9, respectively; these encode isozymes of 1-aminocyclopropane-1-carboxylic acid synthase (ACS), which catalyse the rate-limiting step in ethylene biosynthesis. Here we report that another ethylene-overproducer mutation, eto1, is in a gene that negatively regulates ACS activity and ethylene production. The ETO1 protein directly interacts with and inhibits the enzyme activity of full-length ACS5 but not of a truncated form of the enzyme, resulting in a marked accumulation of ACS5 protein and ethylene. Overexpression of ETO1 inhibited induction of ethylene production by the plant growth regulator cytokinin, and promoted ACS5 degradation by a proteasome-dependent pathway. ETO1 also interacts with CUL3, a constituent of ubiquitin ligase complexes in which we propose that ETO1 serves as a substrate-specific adaptor protein. ETO1 thus has a dual mechanism, inhibiting ACS enzyme activity and targeting it for protein degradation. This permits rapid modulation of the concentration of ethylene.
authors.affiliation: Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
authors.forename: Kevin L-C
authors.initials: KL
authors.lastname: Wang
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Claire
authors.initials: C
authors.lastname: Lurin
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology; D005030:Ethylenes / Q000096:biosynthesis* / Q000378:metabolism; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D008190:Lyases / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; C485242:ETO1 protein, Arabidopsis; D005030:Ethylenes; D009097:Multienzyme Complexes; C036216:ethylene; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase