title: EBS7 is a plant-specific component of a highly conserved endoplasmic reticulum-associated degradation system in Arabidopsis.
abstract: Endoplasmic reticulum (ER)-associated degradation (ERAD) is an essential part of an ER-localized protein quality-control system for eliminating terminally misfolded proteins. Recent studies have demonstrated that the ERAD machinery is conserved among yeast, animals, and plants; however, it remains unknown if the plant ERAD system involves plant-specific components. Here we report that the Arabidopsis ethyl methanesulfonate-mutagenized brassinosteroid-insensitive 1 suppressor 7 (EBS7) gene encodes an ER membrane-localized ERAD component that is highly conserved in land plants. Loss-of-function ebs7 mutations prevent ERAD of brassinosteroid insensitive 1-9 (bri1-9) and bri1-5, two ER-retained mutant variants of the cell-surface receptor for brassinosteroids (BRs). As a result, the two mutant receptors accumulate in the ER and consequently leak to the plasma membrane, resulting in the restoration of BR sensitivity and phenotypic suppression of the bri1-9 and bri1-5 mutants. EBS7 accumulates under ER stress, and its mutations lead to hypersensitivity to ER and salt stresses. EBS7 interacts with the ER membrane-anchored ubiquitin ligase Arabidopsis thaliana HMG-CoA reductase degradation 1a (AtHrd1a), one of the central components of the Arabidopsis ERAD machinery, and an ebs7 mutation destabilizes AtHrd1a to reduce polyubiquitination of bri1-9. Taken together, our results uncover a plant-specific component of a plant ERAD pathway and also suggest its likely biochemical function.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109;
authors.forename: Yidan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 201602, China.
authors.forename: Congcong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 201602, China.
authors.forename: Dinghe
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109;
authors.forename: Wei
authors.initials: W
authors.lastname: Su
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 201602, China.
authors.forename: Linchuan
authors.initials: L
authors.lastname: Liu
authors.affiliation: Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 201602, China.
authors.forename: Muyang
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109; Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, The Chinese Academy of Sciences, Shanghai 201602, China jian@umich.edu.
authors.forename: Jianming
authors.initials: J
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000502:physiology*; D004926:Escherichia coli; D005020:Ethyl Methanesulfonate; D015151:Immunoblotting; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000235:genetics; D030821:Plants, Genetically Modified; D010957:Plasmids / Q000235:genetics; D011494:Protein Kinases; D055550:Protein Stability; D059748:Proteolysis; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020798:Two-Hybrid System Techniques; D056811:Unfolded Protein Response / Q000235:genetics* / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; C000604169:EBS7 protein, Arabidopsis; D008565:Membrane Proteins; D009841:Oligonucleotides; D005020:Ethyl Methanesulfonate; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis
keywords: EMS-mutagenized bri1 suppressor; ERAD; brassinosteroid receptor BRI1; ubiquitin ligase E3; unfolded protein response