Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (U.I., J.E.S., H.J.K., R.E.C., E.B.C.).
Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden (M.A.); and.
Plant Physiol. 2017 May;174(1):97-109. doi: 10.1104/pp.16.01894. Epub 2017 Mar 21.
Seed oils of many sp. contain >90% of medium-chain fatty acids, such as decanoic acid (10:0). These seed oils, which are among the most compositionally variant in the plant kingdom, arise from specialized fatty acid biosynthetic enzymes and specialized acyltransferases. These include lysophosphatidic acid acyltransferases (LPAT) and diacylglycerol acyltransferases (DGAT) that are required for successive acylation of medium-chain fatty acids in the -2 and -3 positions of seed triacylglycerols (TAGs). Here we report the identification of a cDNA for a DGAT1-type enzyme, designated CpuDGAT1, from the transcriptome of var developing seeds. Microsomes of camelina () seeds engineered for CpuDGAT1 expression displayed DGAT activity with 10:0-CoA and the diacylglycerol didecanoyl, that was approximately 4-fold higher than that in camelina seed microsomes lacking CpuDGAT1. In addition, coexpression in camelina seeds of CpuDGAT1 with a FatB thioesterase (CvFatB1) that generates 10:0 resulted in TAGs with nearly 15 mol % of 10:0. More strikingly, expression of CpuDGAT1 and CvFatB1 with the previously described CvLPAT2, a 10:0-CoA-specific LPAT, increased 10:0 amounts to 25 mol % in camelina seed TAG. These TAGs contained up to 40 mol % 10:0 in the -2 position, nearly double the amounts obtained from coexpression of CvFatB1 and CvLPAT2 alone. Although enriched in diacylglycerol, 10:0 was not detected in phosphatidylcholine in these seeds. These findings are consistent with channeling of 10:0 into TAG through the combined activities of specialized LPAT and DGAT activities and demonstrate the biotechnological use of these enzymes to generate 10:0-rich seed oils.
许多 sp. 的种子油含有超过 90%的中链脂肪酸，如癸酸（10:0）。这些种子油是植物界中成分变化最多的油，它们来自于专门的脂肪酸生物合成酶和酰基转移酶。其中包括溶血磷脂酸酰基转移酶（LPAT）和二酰基甘油酰基转移酶（DGAT），它们分别负责在种子三酰基甘油（TAG）的 -2 和 -3 位上连续酰化中链脂肪酸。在这里，我们从 var 发育种子的转录组中鉴定出一个 DGAT1 型酶的 cDNA，命名为 CpuDGAT1。拟南芥种子的微粒体在 CpuDGAT1 表达后，显示出与 10:0-CoA 和二酰基甘油癸酰的 DGAT 活性，大约比缺乏 CpuDGAT1 的拟南芥种子微粒体高 4 倍。此外，在拟南芥种子中共表达 CpuDGAT1 和产生 10:0 的 FatB 硫酯酶（CvFatB1），导致 TAG 中 10:0 的含量几乎达到 15mol%。更引人注目的是，与之前描述的 CvLPAT2（一种 10:0-CoA 特异性 LPAT）一起表达 CpuDGAT1 和 CvFatB1，将 10:0 的含量增加到拟南芥种子 TAG 中的 25mol%。这些 TAG 在 -2 位上含有高达 40mol%的 10:0，几乎是单独共表达 CvFatB1 和 CvLPAT2 获得的含量的两倍。尽管在这些种子中，10:0 在二酰基甘油中被富集，但在磷脂酰胆碱中未检测到 10:0。这些发现与 10:0 通过专门的 LPAT 和 DGAT 活性的联合作用而被定向进入 TAG 的结果一致，并证明了这些酶在产生富含 10:0 的种子油方面的生物技术用途。
