Cyperus esculentus is probably the only plant that is known to accumulate large amounts of oil in its tubers. However, the underlying metabolic mechanism and regulatory factors involved in oil synthesis of tubers are still largely unclear. In this study, one gene encoding type I diacylglycerol acyltransferase (DGAT) (CeDGAT1) and two genes encoding type II DGAT (CeDGAT2a and CeDGAT2b) from C. esculentus were identified and functionally analyzed. All three DGAT genes were found to be expressed in tuber, root and leaf tissues. CeDGAT1 is highly expressed in roots and leaves, whereas CeDGAT2b is dominantly expressed in tubers. Furthermore, the temporal expression pattern of CeDGAT2b is well coordinated with the oil accumulation in developing tubers. When each CeDGAT was heterologously expressed in triacylglycerol (TAG)-deficient mutant of Saccharomyces cerevisiae, Arabidopsis thaliana wild type or its TAG1 mutant with AtDGAT1 disruption, only CeDGAT2b showed the ability to restore TAG biosynthesis with lipid body formation in yeast mutant, enhance seed oil production of Arabidopsis wild type and rescue multiple seed phenotypes of TAG1 mutant. In addition, CeDGAT2b was shown to have a substrate preference for unsaturated fatty acids toward TAG synthesis. Taken together, our results indicated that CeDGAT2b from C. esculentus is an actively functional protein and is most likely the major contributor to tuber oil biosynthesis containing common fatty acids, in contrast to oil-rich seeds and fruits where DGAT1 plays a more central role than DGAT2 in oil production accumulating normal fatty acids, whereas DGAT2 is a primary regulator for oil synthesis rich in unusual fatty acids.

中文翻译：

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香附子富含油的块茎中编码双酰基甘油酰基转移酶（DGAT）的三个新基因的功能表征。

莎草（Cyperus esculentus）可能是唯一已知在其块茎中积累大量油的植物。然而，块茎油合成中涉及的潜在代谢机制和调控因素仍不清楚。在这项研究中，鉴定和功能分析了一个编码I型二酰基甘油酰基转移酶（DGAT）的基因（CeDGAT1）和两个编码II型DGAT的基因（CeDGAT2a和CeDGAT2b）。发现所有三个DGAT基因在块茎，根和叶组织中表达。CeDGAT1在根和叶中高表达，而CeDGAT2b在块茎中占优势。此外，CeDGAT2b的时间表达模式与正在发育的块茎中的油积累很好地协调。当每个CeDGAT在酿酒酵母，拟南芥野生型或其具有AtDGAT1破坏的TAG1突变体的缺乏三酰基甘油（TAG）的突变体中异源表达时，只有CeDGAT2b显示出具有恢复酵母突变体中脂质体形成，增强种子油的TAG生物合成的能力。拟南芥野生型的生产和拯救TAG1突变体的多种种子表型。此外，CeDGAT2b被证明对TAG合成具有不饱和脂肪酸的底物偏爱性。综上所述，我们的结果表明，食肉梭菌中的CeDGAT2b是一种活性功能蛋白，最有可能是含常见脂肪酸的块茎油生物合成的主要贡献者，而富含油的种子和果实中DGAT1比石油生产中的DGAT2积累了正常脂肪酸，