Effect of Thiolactomycin on Lipid Synthesis in Higher Plants

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The effect of thiolactomycin (TLM), an inhibitor of type II fatty acid synthase, on lipid synthesis in greening tissues was examined. Pulse-chase experiments with Na[1-^<14>C]acetate for greening Avena leaves showed that continuous administration of TLM (100 μg/ml) decisively reduced phosphatidylcholine (PC) synthesis from acetate and blocked the subsequent conversion of PC to monogalactocyldiacylglycerol (MGDG), whereas temporal administration of TLM (100 μg/ml) reduced PC synthesis from acetate by only 50% and did not block the conversion of PC to MGDG. In the reduced PC synthesis, the ratio of oleic to palmitic acid decreased at earlier stages of greening, reflecting more suppression of oleic acid synthesis. In later greening stages the modulated fatty acid composition recovered to the normal composition. In further steps, the fatty acid composition was not affected by TLM throughout the greening stages. Greening of either etiolated Avena leaves or etiolated Brassica cotyledons in the presence of TLM led to a marked decrease in the contents of MGDG, digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol (PG), but only a small change in the fatty acid composition of their lipids. The only inhibition characteristic of TLM was the desaturation of palmitic to 3-trans-hexadecenoic acid in Avena leaf PG. These results suggest the presence of a mechanism by which the modulated fatty acid composition of lipids is normalized in the flow of the synthesis. Electron microscopic observations showed that Avena chloroplasts developed into round forms rather than normal ellipse forms and the thylakoid membranes of Brassica chloroplasts were abnormally swollen everywhere in the presence of TLM. Photosynthetic oxygen evolution in both tissues was not inhibited.
日本植物生理学会の論文

Effect of Thiolactomycin on Lipid Synthesis in Higher Plants

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