title: Functional identification of valerena-1,10-diene synthase, a terpene synthase catalyzing a unique chemical cascade in the biosynthesis of biologically active sesquiterpenes in Valeriana officinalis.
abstract: Valerian is an herbal preparation from the roots of Valeriana officinalis used as an anxiolytic and sedative and in the treatment of insomnia. The biological activities of valerian are attributed to valerenic acid and its putative biosynthetic precursor valerenadiene, sesquiterpenes, found in V. officinalis roots. These sesquiterpenes retain an isobutenyl side chain whose origin has been long recognized as enigmatic because a chemical rationalization for their biosynthesis has not been obvious. Using recently developed metabolomic and transcriptomic resources, we identified seven V. officinalis terpene synthase genes (VoTPSs), two that were functionally characterized as monoterpene synthases and three that preferred farnesyl diphosphate, the substrate for sesquiterpene synthases. The reaction products for two of the sesquiterpene synthases exhibiting root-specific expression were characterized by a combination of GC-MS and NMR in comparison to the terpenes accumulating in planta. VoTPS7 encodes for a synthase that biosynthesizes predominately germacrene C, whereas VoTPS1 catalyzes the conversion of farnesyl diphosphate to valerena-1,10-diene. Using a yeast expression system, specific labeled [(13)C]acetate, and NMR, we investigated the catalytic mechanism for VoTPS1 and provide evidence for the involvement of a caryophyllenyl carbocation, a cyclobutyl intermediate, in the biosynthesis of valerena-1,10-diene. We suggest a similar mechanism for the biosynthesis of several other biologically related isobutenyl-containing sesquiterpenes.
authors.affiliation: Plant Biology Program, University of Kentucky, Lexington, Kentucky 40503, USA.
authors.forename: Yun-Soo
authors.initials: YS
authors.lastname: Yeo
authors.forename: S Eric
authors.initials: SE
authors.lastname: Nybo
authors.forename: Amar G
authors.initials: AG
authors.lastname: Chittiboyina
authors.forename: Aruna D
authors.initials: AD
authors.lastname: Weerasooriya
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Wang
authors.forename: Elsa
authors.initials: E
authors.lastname: Góngora-Castillo
authors.forename: Brieanne
authors.initials: B
authors.lastname: Vaillancourt
authors.forename: C Robin
authors.initials: CR
authors.lastname: Buell
authors.forename: Dean
authors.initials: D
authors.lastname: DellaPenna
authors.forename: Mary Dawn
authors.initials: MD
authors.lastname: Celiz
authors.forename: A Daniel
authors.initials: AD
authors.lastname: Jones
authors.forename: Eve Syrkin
authors.initials: ES
authors.lastname: Wurtele
authors.forename: Nick
authors.initials: N
authors.lastname: Ransom
authors.forename: Natalia
authors.initials: N
authors.lastname: Dudareva
authors.forename: Khaled A
authors.initials: KA
authors.lastname: Shaaban
authors.forename: Nidhi
authors.initials: N
authors.lastname: Tibrewal
authors.forename: Suman
authors.initials: S
authors.lastname: Chandra
authors.forename: Troy
authors.initials: T
authors.lastname: Smillie
authors.forename: Ikhlas A
authors.initials: IA
authors.lastname: Khan
authors.forename: Robert M
authors.initials: RM
authors.lastname: Coates
authors.forename: David S
authors.initials: DS
authors.lastname: Watt
authors.forename: Joe
authors.initials: J
authors.lastname: Chappell
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000378:metabolism*; D055162:Biocatalysis; D053898:Biosynthetic Pathways / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006838:Hydrocarbons / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D014632:Valerian / Q000201:enzymology* / Q000235:genetics
chemical_list: D006838:Hydrocarbons; D010940:Plant Proteins; D012717:Sesquiterpenes; D019883:Alkyl and Aryl Transferases; C108877:terpene synthase