Inhibition of oleic acid incorporation into a non-lipid fraction by chloroacetamide herbicides

Abstract

Kring, F., Couderchet, M. and Bbger, P. 1995. Inhibition of oleic acid incorporation into a non-lipid fraction by chloroacetamide herbicides. -Physioi. Plant. 95: 551-558.Oleic acid is incorporated into an insoluble fraction left over afteF lipid exfraction in Scenedesmus acutus. This incorporation is extremely sensitive to the chloroacetamide herbicide, metazachlor (I;(, = ca 20 nM). Therefore, factors influencing tlK incorporation of radioactivity from oleic acid into this non-lipid fraction were investigated. S acutus cells were cultivated under various conditions with or without inhibitors and ('*CJ-oleic acid was supplied to the algae; the lipids were extracted and the radioactivity incorporated in the remaining fraction monitored. The inhibition seemed specific for chloroacetamides and related classes since it was also observed with alachior, dimethenamid and mefenacet (an oxyacetamide). In contrast, it could not be found with diuron. oryzalin, nor could it be observed with a non-herbicidal metazachlor derivative or iodoacetamide. Incorporation of oleic acid into that fraction required metabolically active cells and was stimulated by light. Other fattjf acids (16:0, 18:2, and 18:3) were also incorporated into the non-lipid fraction but their incorporation was not inhibited by metazachior. Among other components, the fraction contains proteins. However, a possible specific effect of chloroacetamides on the binding of oleic acid to proteins or on the in vitro activity of iipid transfer proteins could not be detected. Not much is known yet about mechanism and chemistry of oleic acid incorporation but this finding opens a new path for investigations towards the primary target of these herbicides.