title: Identification of a new glucosinolate-rich cell type in Arabidopsis flower stalk.
abstract: Distribution of K, Ca, Cl, S, and P in freeze-dried sections of Arabidopsis flower stalk was analyzed by energy dispersive x-ray imaging. Concentrations of these elements in different cell types were quantified by microanalysis of single-cell samples and phloem exudates. Results showed a differential pattern of distribution for all five elements. K concentration was found to be highest in the parenchymatous tissue around vascular bundles. Ca and Cl were present mainly in the central part of the flower stalk. P was largely located in the bundles and in the parenchyma surrounding them. S signal was extraordinary high in groups of cells (S-cells) situated between the phloem of every vascular bundle and the endodermis. Enzymatic hydrolysis by thioglucosidase of cell sap collected from S-cells using a glass microcapillary resulted in the release of glucose, indicating that these cells contain glucosinolates at high (> 100 mM) concentration, which is consistent with the concentration of S (> 200 mM) estimated by x-ray analysis of cell sap samples. Since their position outside of the phloem is ideally suited for protecting the long-distance transport system from feeding insects, the possible roles of these cells as components of a plant defense system are discussed.
authors.affiliation: School of Biological Sciences, University of Wales, Bangor LL57 2UW, United Kingdom. o.koroleva@bangor.ac.uk
authors.forename: O A
authors.initials: OA
authors.lastname: Koroleva
authors.forename: A
authors.initials: A
authors.lastname: Davies
authors.forename: R
authors.initials: R
authors.lastname: Deeken
authors.forename: M R
authors.initials: MR
authors.lastname: Thorpe
authors.forename: A D
authors.initials: AD
authors.lastname: Tomos
authors.forename: R
authors.initials: R
authors.lastname: Hedrich
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000166:cytology / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D005961:Glucosinolates / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D005961:Glucosinolates