Diflufenican, a carotenogenesis inhibitor, also reduces acyl lipid synthesis

The bleaching herbicide diflufenican (DFF) has been shown to produce effects on the membranes of sensitive plant tissues which may be independent of its inhibition of carotenoid synthesis. Therefore, we examined whether DFF had any action on acyl lipid metabolism. In leaves from a variety of plants, DFF was shown to inhibit the incorporation of radioactivity from [1- 14 C]acetate and [2- 14 C]malonate into acyl lipids. The labeling of all lipid classes was reduced equally and there was no change in the pattern of fatty acids labeled, suggesting that fatty acid synthesis de novo was affected. Further experiments suggested that fatty acid synthetase rather than acetyl-CoA carboxylase was the site of action. Direct measurement of fatty acid synthetase in soluble fractions from pea and barley leaves and avocado mesocarp confirmed that DFF inhibited the enzyme complex in vitro . The inhibition was competitive against pyridine nucleotides and suggested that one or both of the reductase components of fatty acid synthetase was the target site.