The novel herbicide oxaziclomefone inhibits cell expansion in maize cell cultures without affecting turgor pressure or wall acidification

Abstract

Summary• Oxaziclomefone [OAC; IUPAC name 3-(1-(3,5-dichlorophenyl)-1-methylethyl)-3,4-dihydro-6-methyl-5-phenyl-2 H -1,3-oxazin-4-one] is a new herbicide that inhibits cell expansion in grass roots. Its effects on cell cultures and mode of action were unknown. In principle, cell expansion could be inhibited by a decrease in either turgor pressure or wall extensibility.• Cell expansion was estimated as settled cell volume; cell division was estimated by cell counting. Membrane permeability to water was measured by a novel method involving simultaneous assay of the efflux of 3 H 2 O and [ 14 C]mannitol from a 'bed' of cultured cells. Osmotic potential was measured by depression of freezing point.• OAC inhibited cell expansion in cultures of maize ( Zea mays ), spinach ( Spinacia oleracea ) and rose ( Rosa sp.), with an ID 50 of 5, 30 and 250 n M , respectively. In maize cultures, OAC did not affect cell division for the first 40 h. It did not affect the osmotic potential of cell sap or culture medium, nor did it impede water transport across cell membranes. It did not affect cells' ability to acidify the apoplast (medium), which may be necessary for 'acid growth'.• As OAC did not diminish turgor pressure, its ability to inhibit cell expansion must depend on changes in wall extensibility. It could be a valuable tool for studies on cell expansion.

Oxaziclomefone, a New Herbicide, Inhibits Wall Expansion in Maize Cell-cultures without Affecting Polysaccharide Biosynthesis, Xyloglucan Transglycosylation, Peroxidase Action or Apoplastic Ascorbate Oxidation

“…These processes include: cellulose biosynthesis; wall matrix polysaccharide biosynthesis, including MLG; production, secretion and action of XET activity; production, secretion and action of peroxidase activity; polysaccharide feruloylation; oxidative coupling of feruloyl or p-coumaroyl residues; and consumption of apoplastic ascorbate, a potential source of ƒ OH radicals. In addition, it had been shown previously (O'Looney and Fry, 2005) that OAC does not interfere with the cells' ability to acidify their medium (which may be necessary for 'acid growth').…”

“…Cell expansion is driven by turgor pressure, and in healthy tissues is usually limited by the extensibility of the cell wall or sometimes by the wall yield threshold (Cosgrove, 1993;Kutschera, 2001). In recent work (O'Looney and Fry, 2005) it was found that OAC inhibits cell expansion in maize cell cultures, with an ID 50 (dose causing 50 % inhibition) of approx. 5 nM.…”

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

“…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).…”

Inhibition of acyl‐ACP thioesterase as site of action of the commercial herbicides cumyluron, oxaziclomefone, bromobutide, methyldymron and tebutam

“…So far, the MoA of oxaziclomefone has remained elusive 35,36 and it is therefore classified in the HRAC class 0. Here, we present data on oxaziclomefone that show strong FAT thermal stabilization, strong FAT binding in the active center, strong inhibition of FFA production in the FAT activity assay and the clear FAT-like fingerprint in the P-Profile.…”