Revisiting auxin transport inhibition as a mode of action for herbicides

SCB-1, a semicarbazone, is a phytotoxin with both preemergence and postemergence activity against broadleaves and grasses. It effectively displaced [3H]naptalam bound to a solubilized plasma membrane fraction, with the concentration required for 50% dissociation being 3.5 nM. The intrinsic dissociat...

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Bibliographic Details
Published in:Weed science 1997-09, Vol.45 (5), p.621-627
Main Authors: Subramanian, Mani V., Brunn, Sandra A., Bernasconi, Paul, Patel, Bhavesh C., Reagan, Jeff D.
Format: Article
Language:English
Subjects:
2,4-D
ACTIVE TRANSPORT
AIA
APPLICATION RATES
Auxins
BINDING
Carrier proteins
CELL MEMBRANES
CUCURBITA PEPO
DOSE D'APPLICATION
DOSIS DE APLICACION
FITOTOXICIDAD
HERBICIDAL PROPERTIES
HERBICIDAS
HERBICIDE
HERBICIDES
Hypocotyls
IAA
INHIBICION
INHIBITION
MEMBRANAS CELULARES
MEMBRANE CELLULAIRE
Molybdates
NAPTALAM
P branes
PHYTOTOXICITE
PHYTOTOXICITY
PLANT PROTEINS
PLANTAS
PLANTE
PLANTS
PLASMA MEMBRANES
PROTEINAS
PROTEINE
PROTEINS
Sodium
Solubilization
Symposium
Symposium of Section X—Physiology, Weed Science Society of America, Norfolk, Virginia, 1996
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Summary:SCB-1, a semicarbazone, is a phytotoxin with both preemergence and postemergence activity against broadleaves and grasses. It effectively displaced [3H]naptalam bound to a solubilized plasma membrane fraction, with the concentration required for 50% dissociation being 3.5 nM. The intrinsic dissociation constant (Kd ) for binding of [3H]naptalam to zucchini plasma membranes was estimated to be 9.7 nM. Binding of [3H]naptalam to the solubilized protein fraction from the plasma membrane was rapid, time dependent, saturable, and reversible. The Kd for binding was estimated at 4 nM. Based on the maximum binding of [3H]naptalam, concentration of the binding protein was calculated to be 23.6 and 10.8 pmol mg−1 protein in the plasma membrane and solubilized fraction, respectively. SCB-1 also blocked the efflux of [14C]IAA, resulting in more than 800% accumulation of radiolabel in zucchini squash hypocotyl segments at 5 μM. This accumulation was quenched by excess cold IAA and 2,4-D. Collectively, these results suggest that SCB-1 is a potent inhibitor of auxin efflux and that it competes with naptalam for binding to the plasma membrane protein.
ISSN:0043-1745
1550-2759
DOI:10.1017/S0043174500093231