title: Flavonoids redirect PIN-mediated polar auxin fluxes during root gravitropic responses.
abstract: The rate, polarity, and symmetry of the flow of the plant hormone auxin are determined by the polar cellular localization of PIN-FORMED (PIN) auxin efflux carriers. Flavonoids, a class of secondary plant metabolites, have been suspected to modulate auxin transport and tropic responses. Nevertheless, the identity of specific flavonoid compounds involved and their molecular function and targets in vivo are essentially unknown. Here we show that the root elongation zone of agravitropic pin2/eir1/wav6/agr1 has an altered pattern and amount of flavonol glycosides. Application of nanomolar concentrations of flavonols to pin2 roots is sufficient to partially restore root gravitropism. By employing a quantitative cell biological approach, we demonstrate that flavonoids partially restore the formation of lateral auxin gradients in the absence of PIN2. Chemical complementation by flavonoids correlates with an asymmetric distribution of the PIN1 protein. pin2 complementation probably does not result from inhibition of auxin efflux, as supply of the auxin transport inhibitor N-1-naphthylphthalamic acid failed to restore pin2 gravitropism. We propose that flavonoids promote asymmetric PIN shifts during gravity stimulation, thus redirecting basipetal auxin streams necessary for root bending.
authors: Laboratory of Molecular Plant Physiology, Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland.
authors: Diana
authors: D
authors: Santelia
authors: Sina
authors: S
authors: Henrichs
authors: Vincent
authors: V
authors: Vincenzetti
authors: Michael
authors: M
authors: Sauer
authors: Laurent
authors: L
authors: Bigler
authors: Markus
authors: M
authors: Klein
authors: Aurélien
authors: A
authors: Bailly
authors: Youngsook
authors: Y
authors: Lee
authors: Jirí
authors: J
authors: Friml
authors: Markus
authors: M
authors: Geisler
authors: Enrico
authors: E
authors: Martinoia
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000235:genetics / Q000378:metabolism*; D018522:Gravitropism / Q000187:drug effects / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D010797:Phthalimides / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D005419:Flavonoids; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D010797:Phthalimides; D010937:Plant Growth Regulators; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C002687:alpha-naphthylphthalamic acid