Biosynthesis of stearate-rich triacylglycerol in developing embryos and microsomal membranes from immature seeds of Garcinia indica Chois.

Analysis of fatty acid composition and storage lipid content of Garcinia indica Chois. during seed development showed high stearate content at the early stages, with progressive increase to 60% of the total fatty acids during development. When C-14-acetate was used as a precursor, it was preferentially incorporated into stearate that, in turn, was esterified to triacylglycerol. Kinetics of incorporation of radioactive stearate into diacylglycerol and triacylglycerol was about two fold higher than that of palmitate during various stages of seed development. Pulse-chase experiments with C-14-acetate provided evidence that phosphatidylcholine is involved in donating stearate and oleate for triacylglycerol biosynthesis. When assays were performed for acyltransferase activities in the microsomal membrane fraction with palmitoyl-, stearoyl-, and oleoyl-CoAs, glycerol-3-phosphate acyltransferase and diacylglycerol acyltransferase showed preference for stearoyl-CoA, whereas lysophosphatidic acid acyltransferase had a preference for oleoyl-CoA. These results indicate that stearic acid preferring triacylglycerol biosynthetic machinery exists in the G. indica seeds. These data demonstrate that G. indica seeds are a desirable source of acyltransferases for engineering a high stearic acid phenotype in temperate oilseeds.