Edited by Michael R. SussmanKeywords: AAE15/16 Acyl chain activating enzyme Cuphea Medium chain fatty acid Thioesterase Triacylglycerol a b s t r a c t Engineering transgenic plants that accumulate high levels of medium-chain fatty acids (MCFA) has been least successful for shorter chain lengths (e.g., C8). We demonstrate that one limitation is the activity of acyl-ACP synthetase (AAE) that re-activates fatty acids released by acyl-ACP thioesterases. Seed expression of Cuphea pulcherrima FATB acyl-ACP thioesterase in a double mutant lacking AAE15/16 increased 8:0 accumulation almost 2-fold compared to expression in wild type. These results also provide an in planta demonstration that AAE enzymes participate not only in activation of exogenously added MCFA but also in activation of MCFA synthesized in plastids.

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HighlightAnalysis of flux of exogenously supplied [14C]fatty acid in wild-type and mutant Arabidopsis leaves indicates that DGAT1 is the predominant enzyme involved in triacylglycerol synthesis in young leaves.

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