Flavonoids redirect PIN-mediated polar auxin fluxes during root gravitropic responses.
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.
Santelia
Diana
D
Laboratory of Molecular Plant Physiology, Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland.
Henrichs
Sina
S
Vincenzetti
Vincent
V
Sauer
Michael
M
Bigler
Laurent
L
Klein
Markus
M
Bailly
Aurélien
A
Lee
Youngsook
Y
Friml
Jirí
J
Geisler
Markus
M
Martinoia
Enrico
E
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
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