Fatty acid biosynthesis in the leaves of barley, wheat and pea

Abstract

The incorporation of radioactivity from [1-14C]acetate into the leaf lipids of barley, pea and wheat was studied in pulse-labeling experiments. There was little increase in the total labeling of lipids after the leaves were transferred to non-radioactive medium. However, there was an increase in the relative labeling of unsaturated fatty acids. In addition, there was an increase in the relative labeling of diacylgalactosylglycerol. The principal radioactively labeled acyl lipids were diacylgalactosylglycerol and phosphatidylcholine. Phosphatidylcholine showed a decreasing proportion of [14C]oleate and an increasing amount of [14C]linoleate with time. Diacylgalactosylglycerol also had decreasing amounts of [14C]oleate but, in addition, had an increasing proportion of [14C]linolenate with time. The absence of significant amounts of [14C]linolenate in phosphatidylcholine appeared to exclude a role for this phospholipid in linoleate desaturation. The specific radioactivities of oleate and linoleate in phosphatidylcholine, diacylgalactosylglycerol and diacylgalabiosylglycerol were very similar in any single experiment. Apparently these fatty acids can rapidly exchange between the 3 intact lipids.