Seed-specific expression of an acyl-acyl carrier protein thioesterase CnFatB3 from coconut (Cocos nucifera L.) increases the accumulation of medium-chain fatty acids in transgenic Arabidopsis seeds

Coconut (Cocos nucifers L.) can accumulate up to nearly 80% of medium-chain fatty acids (MCFAs) in its endosperm. A previous study about suppression subtractive hybridization (SSH) libraries of coconut endosperm indicated that only one acyl-acyl carrier protein (ACP) thioesterase CnFatB3 was identified and significantly up-regulated during fruit development. Overexpression of CnFatB3 cDNA in Arabidopsis under control of the seed-specific napin promoter increased the amounts of 12:0 (lauric acid), 14:0 (myristic acid), 16:0 (palmitic acid) and 18:0 (stearic acid) by 30, 80, 4, and 2-fold, respectively, although CnFatB3 transcript levels varied 4000-fold in Arabidopsis seeds from different transgenic lines. These data suggested that CnFatB3 had a preference for 12:0, 14:0, 16:0 and 18:0-ACPs in plant. The results provide new insights into the accumulation of MCFAs in higher plants, and will contribute to the metabolic engineering of MCFAs-producing to meet energy demands.