Effects of the herbicide EPTC and the protectant DDCA on incorporation and distribution of [2- 14C]acetate into major lipid fractions of maize cell suspension cultures

Abstract

The rapid effects of the herbicide EPTC ( S-ethyl dipropylthiocarbamate) and the protectant DDCA ( N,N-diallyl-2,2-dichloroacetamide) on [2- 14C]acetate incorporation into lipids of maize cell cultures were studied in order to determine whether they act at similar sites of lipid synthesis. DDCA, at 0.05 m M and 0.1 m M, increased the incorporation of [2- 14C]acetate into neutral lipids of a total lipid extract within 2 h. It had very little effect on the major polar lipid constituents. DDCA altered neither the distribution of label within the major lipid classes, nor turnover of the major lipids within 2 h. EPTC (0.1 m M) inhibited overall uptake of [2- 14C]acetate into both neutral and polar lipids by about 30% after a 2-h incubation. The major polar lipid affected was an unidentified glycolipid. In addition to reducing the quantity of lipids synthesized, EPTC changed the lipid profile, altering the distribution of label, mainly within the neutral lipid fraction. A crude membrane fraction from maize cells contained both polar lipids and some neutral lipids. DDCA stimulated [2- 14C]acetate incorporation into different lipid species. EPTC inhibited incorporation of [2- 14C]acetate into both neutral and polar membrane lipids but altered significantly only its distribution into neutral lipids. DDCA (0.1 m M) given together with EPTC (0.2 m M) partially counteracted the effect of EPTC within the neutral lipid fraction. It is suggested that DDCA has a rapid effect on lipid synthesis, but it is probably not sufficient to account for the entire mode of action of the protectant.