EBS7 is a plant-specific component of a highly conserved endoplasmic reticulum-associated degradation system in Arabidopsis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 39; pp. 12205 - 12210
• Main Authors: Liu, Yidan, Zhang, Congcong, Wang, Dinghe, Su, Wei, Liu, Linchuan, Wang, Muyang, Li, Jianming
• Format: Journal Article
• Language: English
• Published: United States National Acad Sciences 29.09.2015; National Academy of Sciences
• Subjects: Amino Acid Sequence; Arabidopsis - genetics; Arabidopsis Proteins - antagonists & inhibitors; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Base Sequence; Biochemistry; Biological Sciences; Cloning, Molecular; Endoplasmic reticulum; Endoplasmic Reticulum - physiology; Escherichia coli; Ethyl Methanesulfonate; Genetics; Immunoblotting; Membrane Proteins - genetics; Membrane Proteins - metabolism; Microscopy, Confocal; Molecular Sequence Data; Mutation; Oligonucleotides - genetics; Plant biology; Plants, Genetically Modified; Plasmids - genetics; Protein folding; Protein Kinases; Protein Stability; Proteolysis; Sequence Alignment; Sequence Analysis, DNA; Stress response; Two-Hybrid System Techniques; Unfolded Protein Response - genetics; Unfolded Protein Response - physiology; ERAD; unfolded protein response; ubiquitin ligase E3; brassinosteroid receptor BRI1; EMS-mutagenized bri1 suppressor
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1511724112

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.