title: Unique cellular effect of the herbicide bromoxynil revealed by electrophysiological studies using characean cells.
abstract: In a previous paper, we proposed that the primary action of the herbicide bromoxynil (BX; 3,5-dibromo-4-hydroxybenzonitrile) is cytosol acidification, based on the fact that bromoxynil induced the inhibition of cytoplasmic streaming and cell death of Chara corallina in acidic external medium (Morimoto and Shimmen in J Plant Res 121:227-233, 2008). In the present study, electrophysiological analysis of the BX effect was carried out in internodal cells of C. corallina. Upon addition of BX, a large and rapid pH-dependent depolarization was induced, supporting our hypothesis. Ioxynil, which belongs to the same group as bromoxynil, also induced a large and rapid membrane depolarization in a pH-dependent manner. On the other hand, four herbicides belonging to other groups of herbicides did not induce such a membrane depolarization. Thus, BX has a unique cellular effect. The decrease in the electro-chemical potential gradient for H(+) across the plasma membrane appears to result in inhibition of cell growth and disturbance of intracellular homeostasis in the presence of BX.
authors.affiliation: Department of Life Science, Graduate School of Life Science, University of Hyogo, Harima Science Park City, Hyogo, Japan. shimmen@sci.u-hyogo.ac.jp
authors.forename: Teruo
authors.initials: T
authors.lastname: Shimmen
mesh_terms: D016923:Cell Death / Q000187:drug effects; D044784:Chara / Q000187:drug effects / Q000502:physiology; D006540:Herbicides / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007462:Iodobenzenes / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009570:Nitriles / Q000494:pharmacology*
chemical_list: D006540:Herbicides; D007462:Iodobenzenes; D009570:Nitriles; C008161:ioxynil; C006826:bromoxynil