title: Isoflavonoid exudation from white lupin roots is influenced by phosphate supply, root type and cluster-root stage.
abstract: The internal concentration of isoflavonoids in white lupin (Lupinus albus) cluster roots and the exudation of isoflavonoids by these roots were investigated with respect to the effects of phosphorus (P) supply, root type and cluster-root developmental stage. To identify and quantify the major isoflavonoids exuded by white lupin roots, we used high-pressure liquid chromatography (HPLC) coupled to electrospray ionization (ESI) in mass spectrometry (MS). The major exuded isoflavonoids were identified as genistein and hydroxygenistein and their corresponding mono- and diglucoside conjugates. Exudation of isoflavonoids during the incubation period used was higher in P-deficient than in P-sufficient plants and higher in cluster roots than in noncluster roots. The peak of exudation occurred in juvenile and immature cluster roots, while exudation decreased in mature cluster roots.Cluster-root exudation activity was characterized by a burst of isoflavonoids at the stage preceding the peak of organic acid exudation. The potential involvement of ATP-citrate lyase in controlling citrate and isoflavonoid exudation is discussed, as well as the possible impact of phenolics in repelling rhizosphere microbial citrate consumers.
authors.affiliation: Laboratory of Molecular Plant Physiology, Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland. laure.weisskopf@unine.ch
authors.forename: Laure
authors.initials: L
authors.lastname: Weisskopf
authors.forename: Nicola
authors.initials: N
authors.lastname: Tomasi
authors.forename: Diana
authors.initials: D
authors.lastname: Santelia
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Nicolas Bernard
authors.initials: NB
authors.lastname: Langlade
authors.forename: Raffaele
authors.initials: R
authors.lastname: Tabacchi
authors.forename: Eliane
authors.initials: E
authors.lastname: Abou-Mansour
mesh_terms: D002853:Chromatography, Liquid; D005419:Flavonoids / Q000032:analysis / Q000378:metabolism*; D031297:Lupinus / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D010710:Phosphates