title: The protein quality control system manages plant defence compound synthesis.
abstract: Jasmonates are ubiquitous oxylipin-derived phytohormones that are essential in the regulation of many development, growth and defence processes. Across the plant kingdom, jasmonates act as elicitors of the production of bioactive secondary metabolites that serve in defence against attackers. Knowledge of the conserved jasmonate perception and early signalling machineries is increasing, but the downstream mechanisms that regulate defence metabolism remain largely unknown. Here we show that, in the legume Medicago truncatula, jasmonate recruits the endoplasmic-reticulum-associated degradation (ERAD) quality control system to manage the production of triterpene saponins, widespread bioactive compounds that share a biogenic origin with sterols. An ERAD-type RING membrane-anchor E3 ubiquitin ligase is co-expressed with saponin synthesis enzymes to control the activity of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), the rate-limiting enzyme in the supply of the ubiquitous terpene precursor isopentenyl diphosphate. Thus, unrestrained bioactive saponin accumulation is prevented and plant development and integrity secured. This control apparatus is equivalent to the ERAD system that regulates sterol synthesis in yeasts and mammals but that uses distinct E3 ubiquitin ligases, of the HMGR degradation 1 (HRD1) type, to direct destruction of HMGR. Hence, the general principles for the management of sterol and triterpene saponin biosynthesis are conserved across eukaryotes but can be controlled by divergent regulatory cues.
authors.affiliation: 1] Department of Plant Systems Biology, VIB, Technologiepark 927, Gent B-9052, Belgium [2] Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 927, Gent B-9052, Belgium [3].
authors.forename: Jacob
authors.initials: J
authors.lastname: Pollier
authors.forename: Tessa
authors.initials: T
authors.lastname: Moses
authors.forename: Miguel
authors.initials: M
authors.lastname: González-Guzmán
authors.forename: Nathan
authors.initials: N
authors.lastname: De Geyter
authors.forename: Saskia
authors.initials: S
authors.lastname: Lippens
authors.forename: Robin
authors.initials: R
authors.lastname: Vanden Bossche
authors.forename: Peter
authors.initials: P
authors.lastname: Marhavý
authors.forename: Anna
authors.initials: A
authors.lastname: Kremer
authors.forename: Kris
authors.initials: K
authors.lastname: Morreel
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Guérin
authors.forename: Aldo
authors.initials: A
authors.lastname: Tava
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Oleszek
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
authors.forename: Narciso
authors.initials: N
authors.lastname: Campos
authors.forename: Sofie
authors.initials: S
authors.lastname: Goormachtig
authors.forename: Alain
authors.initials: A
authors.lastname: Goossens
mesh_terms: D002478:Cells, Cultured; D060746:Endoplasmic Reticulum-Associated Degradation; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D005816:Genetic Complementation Test; D046913:Medicago truncatula / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D012503:Saponins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D010937:Plant Growth Regulators; D012503:Saponins; D044767:Ubiquitin-Protein Ligases