Key message

Differences in FAE1 enzyme affinity for the acyl-CoA substrates, as well as the balance between the different pathways involved in their incorporation to triacylglycerol might be determinant of the different composition of the seed oil in Brassicaceae.

Abstract

Brassicaceae present a great heterogeneity of seed oil and fatty acid composition, accumulating Very Long Chain Fatty Acids with industrial applications. However, the molecular determinants of these differences remain elusive. We have studied the β-ketoacyl-CoA synthase from the high erucic feedstock Thlaspi arvense (Pennycress). Functional characterization of the Pennycress FAE1 enzyme was performed in two Arabidopsis backgrounds; Col-0, with less than 2.5% of erucic acid in its seed oil and the fae1-1 mutant, deficient in FAE1 activity, that did not accumulate erucic acid. Seed-specific expression of the Pennycress FAE1 gene in Col-0 resulted in a 3 to fourfold increase of erucic acid content in the seed oil. This increase was concomitant with a decrease of eicosenoic acid levels without changes in oleic ones. Interestingly, only small changes in eicosenoic and erucic acid levels occurred when the Pennycress FAE1 gene was expressed in the fae1-1 mutant, with high levels of oleic acid available for elongation, suggesting that the Pennycress FAE1 enzyme showed higher affinity for eicosenoic acid substrates, than for oleic ones in Arabidopsis. Erucic acid was incorporated to triacylglycerol in the transgenic lines without significant changes in their levels in the diacylglycerol fraction, suggesting that erucic acid was preferentially incorporated to triacylglycerol via DGAT1. Expression analysis of FAE1, AtDGAT1, AtLPCAT1 and AtPDAT1 genes in the transgenic lines further supported this conclusion. Differences in FAE1 affinity for the oleic and eicosenoic substrates among Brassicaceae, as well as their incorporation to triacylglycerol might explain the differences in composition of their seed oil.

中文翻译：

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来自生物燃料原料 Thlaspi arvense 的 β-酮脂酰辅酶 A 合酶的功能分析揭示了十字花科植物三酰甘油生物合成途径的差异。

关键信息

FAE1 酶对酰基辅酶A 底物亲和力的差异，以及它们与三酰基甘油结合所涉及的不同途径之间的平衡可能是十字花科种子油不同组成的决定因素。

抽象的

十字花科的种子油和脂肪酸组成具有很大的异质性，积累了具有工业应用的超长链脂肪酸。然而，这些差异的分子决定因素仍然难以捉摸。我们研究了来自高芥酸原料Thlaspi arvense (Pennycress) 的 β-酮脂酰辅酶 A 合酶。在两种拟南芥背景中进行了 Pennycress FAE1 酶的功能表征；Col-0 的种子油中芥酸含量低于 2.5%，而fae1-1突变体缺乏 FAE1 活性，不会积累芥酸。Pennycress FAE1的种子特异性表达Col-0 中的基因导致种子油中芥酸含量增加了 3 到 4 倍。这种增加伴随着二十碳烯酸水平的降低，而油酸水平没有变化。有趣的是，当 Pennycress FAE1基因在fae1-1突变体中表达时，二十碳烯酸和芥酸水平只有很小的变化，高水平的油酸可用于延伸，这表明 Pennycress FAE1 酶对二十碳烯酸底物表现出更高的亲和力，比拟南芥中的油酸。芥酸在转基因品系中掺入到甘油三酯中，而甘油二酯部分的水平没有显着变化，这表明芥酸通过 DGAT1 优先掺入到甘油三酯中。的表达分析转基因品系中的FAE1、AtDGAT1、AtLPCAT1和AtPDAT1基因进一步支持了这一结论。FAE1 对十字花科油酸和二十碳烯底物的亲和力差异以及它们与三酰基甘油的结合可能解释了其种子油成分的差异。