Plant Physiol.
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Plant Physiology 66:1048-1052 (1980)
© 1980 American Society of Plant Biologists

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Articles

Mode of Dinitroaniline Herbicide Action

II. CHARACTERIZATION OF [14C]ORYZALIN UPTAKE AND BINDING 1

Mahesh K. Upadhyaya2 and Larry D. Noodén

Botany Department, University of Michigan, Ann Arbor, Michigan 48109

The intracellular binding of dinitroaniline herbicides was studied in order to analyze the mechanism of their colchicine-like action. When corn root apices (5 millimeters) are incubated in [14C]oryzalin (a dinitroaniline herbicide), the 14C is taken up rapidly, reaching a plateau in about 4 hours, which corresponds to the minimum incubation time in oryzalin required to get maximum inhibition of elongation. At 4 hours, the [14C]oryzalin concentration inside the roots is 35 times higher than that in the incubation medium. Since this accumulation of [14C]oryzalin is not affected by 1 millimolar sodium azide and there is no metabolism of [14C]oryzalin under these conditions, the [14C]oryzalin must be accumulated (bound) in corn root apices by a process not requiring metabolic energy.

Molecular sieve chromatography (Sephadex G-200) does not show any binding of [14C]oryzalin to any protein with molecular weight similar to the microtubule-subunit protein in rat brain or corn root extracts. However, a massive binding of [14C]oryzalin occurs in the insoluble fraction of corn root extracts. This binding is not localized in any particle size range, is not affected by sonication, is of high capacity, and is a loose (low affinity) association with the binding sites. These binding sites could be solubilized with membrane detergents, which suggests that oryzalin may bind to cellular membranes. Since boiling the homogenate does not affect [14C]oryzalin binding, oryzalin more likely binds to a lipid rather than a protein component of cellular membranes.

2 Present address: Departments of Biology and Crop Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N OWO.

1 This work was supported in part by the Division of Biological Sciences, Cancer Research Institute, the Horace H. Rackham School of Graduate Studies of the University of Michigan, and Lilly Research Laboratory, Greenfield, Indiana.




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F. E. Dayan, J. Howell, and J. D. Weidenhamer
Dynamic root exudation of sorgoleone and its in planta mechanism of action
J. Exp. Bot., May 1, 2009; 60(7): 2107 - 2117.
[Abstract] [Full Text] [PDF]


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