Yang Zhenle, Ji Hongying, Liu Dantong
Key Lab of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China
Key Lab of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China.
Plant Cell Physiol. 2016 Dec;57(12):2519-2540. doi: 10.1093/pcp/pcw165. Epub 2016 Oct 13.
Cyperus esculentus is unique in that it can accumulate rich oil in its tubers. However, the underlying mechanism of tuber oil biosynthesis is still unclear. Our transcriptional analyses of the pathways from pyruvate production up to triacylglycerol (TAG) accumulation in tubers revealed many distinct species-specific lipid expression patterns from oil seeds and fruits, indicating that in C. esculentus tuber: (i) carbon flux from sucrose toward plastid pyruvate could be produced mostly through the cytosolic glycolytic pathway; (ii) acetyl-CoA synthetase might be an important contributor to acetyl-CoA formation for plastid fatty acid biosynthesis; (iii) the expression pattern for stearoyl-ACP desaturase was associated with high oleic acid composition; (iv) it was most likely that endoplasmic reticulum (ER)-associated acyl-CoA synthetase played a significant role in the export of fatty acids between the plastid and ER; (v) lipid phosphate phosphatase (LPP)-δ was most probably related to the formation of the diacylglycerol (DAG) pool in the Kennedy pathway; and (vi) diacylglyceroltransacylase 2 (DGAT2) and phospholipid:diacylglycerolacyltransferase 1 (PDAT1) might play crucial roles in tuber oil biosynthesis. In contrast to oil-rich fruits, there existed many oleosins, caleosins and steroleosins with very high transcripts in tubers. Surprisingly, only a single ortholog of WRINKLED1 (WRI1)-like transcription factor was identified and it was poorly expressed during tuber development. Our study not only provides insights into lipid metabolism in tuber tissues, but also broadens our understanding of TAG synthesis in oil plants. Such knowledge is of significance in exploiting this oil-rich species and manipulating other non-seed tissues to enhance storage oil production.
油莎豆的独特之处在于其块茎能够积累丰富的油脂。然而，块茎油脂生物合成的潜在机制仍不清楚。我们对块茎中从丙酮酸生成到三酰甘油（TAG）积累的途径进行了转录分析，结果显示出许多与油籽和果实不同的物种特异性脂质表达模式，这表明在油莎豆块茎中：（i）从蔗糖到质体丙酮酸的碳通量主要通过胞质糖酵解途径产生；（ii）乙酰辅酶A合成酶可能是质体脂肪酸生物合成中乙酰辅酶A形成的重要贡献者；（iii）硬脂酰-ACP去饱和酶的表达模式与高油酸组成相关；（iv）内质网（ER）相关的酰基辅酶A合成酶很可能在质体和ER之间的脂肪酸输出中起重要作用；（v）脂质磷酸磷酸酶（LPP）-δ很可能与肯尼迪途径中甘油二酯（DAG）池的形成有关；（vi）二酰甘油转酰基酶2（DGAT2）和磷脂：二酰甘油酰基转移酶1（PDAT1）可能在块茎油脂生物合成中起关键作用。与富含油脂的果实不同，块茎中存在许多转录本水平非常高的油质蛋白、钙结合油质蛋白和固醇油质蛋白。令人惊讶的是，仅鉴定出一个类似WRINKLED1（WRI1）的转录因子直系同源物，并且它在块茎发育过程中表达水平很低。我们的研究不仅为块茎组织中的脂质代谢提供了见解，还拓宽了我们对油料植物中TAG合成的理解。这些知识对于开发这种富含油脂的物种以及操纵其他非种子组织以提高储存油脂产量具有重要意义。
