3,7-Dichloroquinolinecarboxylic Acid Inhibits Cell-Wall Biosynthesis in Maize Roots

Abstract

The mode of action of the herbicide 3,7-dichloroquinolinecar-boxylic acid (quinclorac) was examined by measuring incorporation of [14C]glucose, [14C]acetate, [3H]thymidine, and [3H]uridine into maize (Zea mays) root cell walls, fatty acids, DNA, and RNA, respectively. Among the precursors examined, 10 [mu]M quinclorac inhibited [14C]glucose incorporation into the cell wall within 3 h. Fatty acid and DNA biosynthesis were subsequently inhibited, whereas RNA biosynthesis was unaffected. In contrast to the cellulose synthesis inhibitor 2,6-dichlorobenzonitrile, quinclorac strongly inhibited cellulose and a hemicellulose fraction presumed to be glucuronoarabinoxylan. However, the synthesis of (1–>3),(1–>4)-β-D-glucans was only slightly inhibited. The degree of inhibition was time- and dose-dependent. By 4 h after treatment, the concentration that inhibited [14C]glucose incorporation into the cell wall, cellulose, and the sensitive hemicellulose fraction by 50% was about 15, 5, and 20 [mu]M, respectively. Concomitant with an inhibition of [14C]glucose incorporation into the cell wall, quinclorac treatment led to a marked accumulation of radioactivity in the cytosol. The increased radioactivity was found mostly in glucose and fructose. However, total levels of glucose, fructose, and uridine diphosphate-glucose were not changed greatly by quinclorac. These data suggest that quinclorac acts primarily as a cell-wall biosynthesis inhibitor in a susceptible grass by a mechanism that is different from that of 2,6-dichlorobenzonitrile.

Integrative Theory of the Mode of Action of Quinclorac: Literature Review1

“…When quinclorac was applied to Zea mays and Digitaria ischaemum, it inhibited their growth, changed the flow of electrons on young tissues and caused the tissue necrosis on the elongation zone of these monocots (Koo et al, 1994). Due to these symptoms and to other physiological responses, it was stated that Integrative theory of the mode of action of quinclorac: literature review these responses would be associated to the inhibition of the cellular expansion (Koo et al, 1996). Similar effects are found in other herbicides that inhibit cell wall synthesis, such as oxaziclomefone (O'Looney & Fry, 2005) and diclobenil (Peng et al, 2001;DeBolt et al, 2007;Wightman & Turner, 2010).…”

“…According to the physiology of the plant species (as described) and the concentration of quinclorac, the biosynthesis of the cellular wall may be inhibited (Koo et al, 1996). Three hours after the application of quinclorac on corn, it was observed that GAX and cellulose were notably inhibited, while MG was inhibited five hours after spraying (Koo et al, 1996).…”

“…Researches developed during the 1990's showed that quinclorac inhibits the glucose incorporation on the cellular wall, mainly for cellulose (Koo et al, 1996(Koo et al, , 1997. When quinclorac was applied to Zea mays and Digitaria ischaemum, it inhibited their growth, changed the flow of electrons on young tissues and caused the tissue necrosis on the elongation zone of these monocots (Koo et al, 1994).…”

“…Even after 20 years since the commercial release of quinclorac, there are still some controversies on its mode of action (Alonso-Simón et al, 2008). Among the likely modes of action of quinclorac are the inhibition of the cellular wall (Koo et al, 1996(Koo et al, , 1997, auxinic action (Abdallah et al, 2006;Grossmann, 2010), in addition to the ability to stimulate the production of oxygen reactive species (ROS) (Sunohara et al, 2008(Sunohara et al, , 2010. The objectives of this literature review were to show evidence of three hypotheses on the biochemical action of quinclorac and to suggest an integrative and innovative mode of action.…”

Quinclorac-habituation of bean ( Phaseolus vulgaris ) cultured cells is related to an increase in their antioxidant capacity

“…It was previously reported that quinclorac inhibits the incorporation of glucose into cellulose in a dose and time-dependent manner (Koo et al, 1996(Koo et al, , 1997, being regarded as a cellulose biosynthesis inhibitor (CBI) (Vaughn, 2002). However, other works challenged the correlation of cellulose inhibition effect and quinclorac mechanism of action (Tresch and Grossmann, 2003).…”