title: Arabidopsis EIN3-binding F-box 1 and 2 form ubiquitin-protein ligases that repress ethylene action and promote growth by directing EIN3 degradation.
abstract: Ubiquitination of various intracellular proteins by ubiquitin-protein ligases (or E3s) plays an essential role in eukaryotic cell regulation primarily through its ability to selectively target proteins for degradation by the 26S proteasome. Skp1, Cullin, F-box (SCF) complexes are one influential E3 class that use F-box proteins to deliver targets to a core ligase activity provided by the Skp1, Cullin, and Rbx1 subunits. Almost 700 F-box proteins can be found in Arabidopsis, indicating that SCF E3s likely play a pervasive role in plant physiology and development. Here, we describe the reverse genetic analysis of two F-box proteins, EBF1 and -2, that work coordinately in SCF complexes to repress ethylene action. Mutations in either gene cause hypersensitivity to exogenous ethylene and its precursor 1-aminocyclopropane-1-carboxylic acid. EBF1 and -2 interact directly with ethylene insensitive 3 (EIN3), a transcriptional regulator important for ethylene signaling. Levels of EIN3 are increased in mutants affecting either EBF1 or -2, suggesting that the corresponding SCF complexes work together in EIN3 breakdown. Surprisingly, double ebf1 ebf2 mutants display a substantial arrest of seedling growth and have elevated EIN3 levels, even in the absence of exogenous ethylene. Collectively, our results show that the SCF(EBF1/EBF2)-dependent ubiquitination and subsequent removal of EIN3 is critical not only for proper ethylene signaling but also for growth in plants.
authors.affiliation: Department of Genetics, University of Wisconsin, Madison, WI 53706-1574, USA.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Gagne
authors.forename: Jan
authors.initials: J
authors.lastname: Smalle
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Gingerich
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Walker
authors.forename: Sang-Dong
authors.initials: SD
authors.lastname: Yoo
authors.forename: Shuichi
authors.initials: S
authors.lastname: Yanagisawa
authors.forename: Richard D
authors.initials: RD
authors.lastname: Vierstra
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005030:Ethylenes / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C106987:EIN3 protein, Arabidopsis; D005030:Ethylenes; D009687:Nuclear Proteins; D014157:Transcription Factors; C036216:ethylene; D043743:Ubiquitin-Protein Ligase Complexes; C470292:UPL2 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; C470290:UPL1 protein, Arabidopsis