title: Localization of sesquiterpene lactone biosynthesis in cells of capitate glandular trichomes of Helianthus annuus (Asteraceae).
abstract: Capitate glandular trichomes (CGT) of sunflower, Helianthus annuus, synthesize bioactive sesquiterpene lactones (STLs) within a short period of only a few days during trichome development. In the current project, the subcellular localization of H. annuus germacrene A monooxygenase (HaGAO), a key enzyme of the STL biosynthesis in sunflower CGT, was investigated. A polyclonal antibody raised against this enzyme was used for immunolabelling. HaGAO was found in secretory and stalk cells of CGT. This correlated with the appearance of smooth endoplasmic reticulum in both cell types. Stalk cells and secretory cells differed in form, size and types of plastids, but both had structures necessary for secretion. No HaGAO-specific immunoreaction was found in sunflower leaf tissue outside of CGT or in developing CGT before the secretory phase had started. Our results indicated that not only secretory cells but also nearly all cells of the CGT were involved in the biosynthesis of STL and that this process was not linked to the presence or absence of a specific type of plastid.
authors.affiliation: Institute of Botany, University Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Amrehn
authors.affiliation: Institute of Botany, University Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
authors.forename: Anna-Katharina
authors.initials: AK
authors.lastname: Aschenbrenner
authors.affiliation: Institute of Botany, University Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
authors.forename: Annerose
authors.initials: A
authors.lastname: Heller
authors.affiliation: Institute of Botany, University Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany. spring@uni-hohenheim.de.
authors.forename: Otmar
authors.initials: O
authors.lastname: Spring
mesh_terms: D053898:Biosynthetic Pathways; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006368:Helianthus / Q000378:metabolism* / Q000648:ultrastructure; D007783:Lactones / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D012717:Sesquiterpenes / Q000378:metabolism*; D064201:Trichomes / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D007783:Lactones; D010940:Plant Proteins; D012717:Sesquiterpenes; D003577:Cytochrome P-450 Enzyme System; C431677:germacrene A hydroxylase
keywords: Capitate glandular trichomes; Fluorescence microscopy; Immunolabelling; Sesquiterpene lactone biosynthesis; Sunflower; Transmission electron microscopy; Ultrastructure