title: Identification and characterization of two bisabolene synthases from linear glandular trichomes of sunflower (Helianthus annuus L., Asteraceae).
abstract: Sunflower is known to produce a variety of bisabolene-type sesquiterpenes and accumulates these substances in trichomes of leaves, stems and flowering parts. A bioinformatics approach was used to identify the enzyme responsible for the initial step in the biosynthesis of these compounds from its precursor farnesyl pyrophosphate. Based on sequence similarity with a known bisabolene synthases from Arabidopsis thaliana AtTPS12, candidate genes of Helianthus were searched in EST-database and used to design specific primers. PCR experiments identified two candidates in the RNA pool of linear glandular trichomes of sunflower. Their sequences contained the typical motifs of sesquiterpene synthases and their expression in yeast functionally characterized them as bisabolene synthases. Spectroscopic analysis identified the stereochemistry of the product of both enzymes as (Z)-γ-bisabolene. The origin of the two sunflower bisabolene synthase genes from the transcripts of linear trichomes indicates that they may be involved in the synthesis of sesquiterpenes produced in these trichomes. Comparison of the amino acid sequences of the sunflower bisabolene synthases showed high similarity with sesquiterpene synthases from other Asteracean species and indicated putative evolutionary origin from a β-farnesene synthase.
authors.affiliation: Institute of Botany, University of Hohenheim, Garbenstraße 30, 70593 Stuttgart, Germany.
authors.forename: Anna-Katharina
authors.initials: AK
authors.lastname: Aschenbrenner
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
authors.forename: Moonhyuk
authors.initials: M
authors.lastname: Kwon
authors.affiliation: Bioorganic Chemistry, University of Hohenheim, Garbenstraße 30, 70593 Stuttgart, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Conrad
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
authors.forename: Dae-Kyun
authors.initials: DK
authors.lastname: Ro
authors.affiliation: Institute of Botany, University of Hohenheim, Garbenstraße 30, 70593 Stuttgart, Germany. Electronic address: O.Spring@uni-hohenheim.de.
authors.forename: Otmar
authors.initials: O
authors.lastname: Spring
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000302:isolation & purification* / Q000378:metabolism; D006368:Helianthus / Q000737:chemistry / Q000201:enzymology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D013237:Stereoisomerism; D064201:Trichomes / Q000378:metabolism*
chemical_list: D019883:Alkyl and Aryl Transferases
keywords: Bisabolene synthase; Enzyme phylogeny; Helianthus annuus L. (Asteraceae); Linear glandular trichome; Sesquiterpene biosynthesis; Sunflower