State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, People's Republic of China.
Plant Physiol. 2011 Jun;156(2):873-83. doi: 10.1104/pp.111.175950. Epub 2011 Apr 22.
Triacylglycerol (TAG) is the major seed storage lipid and is important for biofuel and other renewable chemical uses. Acyl-coenzyme A:diacylglycerol acyltransferase1 (DGAT1) is the rate-limiting enzyme in the TAG biosynthesis pathway, but the mechanism of its regulation is unknown. Here, we show that TAG accumulation in Arabidopsis (Arabidopsis thaliana) seedlings increased significantly during nitrogen deprivation (0.1 mm nitrogen) with concomitant induction of genes involved in TAG biosynthesis and accumulation, such as DGAT1 and OLEOSIN1. Nitrogen-deficient seedlings were used to determine the key factors contributing to ectopic TAG accumulation in vegetative tissues. Under low-nitrogen conditions, the phytohormone abscisic acid plays a crucial role in promoting TAG accumulation in Arabidopsis seedlings. Yeast one-hybrid and electrophoretic mobility shift assays demonstrated that ABSCISIC ACID INSENSITIVE4 (ABI4), an important transcriptional factor in the abscisic acid signaling pathway, bound directly to the CE1-like elements (CACCG) present in DGAT1 promoters. Genetic studies also revealed that TAG accumulation and DGAT1 expression were reduced in the abi4 mutant. Taken together, our results indicate that abscisic acid signaling is part of the regulatory machinery governing TAG ectopic accumulation and that ABI4 is essential for the activation of DGAT1 in Arabidopsis seedlings during nitrogen deficiency.
甘油三酯（TAG）是主要的种子储存脂质，对于生物燃料和其他可再生化学品的应用非常重要。酰基辅酶 A：二酰基甘油酰基转移酶 1（DGAT1）是 TAG 生物合成途径中的限速酶，但它的调节机制尚不清楚。在这里，我们表明在氮饥饿（0.1mm 氮）期间，拟南芥（Arabidopsis thaliana）幼苗中的 TAG 积累显著增加，同时诱导了参与 TAG 生物合成和积累的基因，如 DGAT1 和油质蛋白 1。利用氮饥饿的幼苗来确定导致营养组织中异位 TAG 积累的关键因素。在低氮条件下，植物激素脱落酸在促进拟南芥幼苗中 TAG 积累方面起着至关重要的作用。酵母单杂交和电泳迁移率变动分析表明，脱落酸信号通路中的一个重要转录因子 ABSCISIC ACID INSENSITIVE4（ABI4）直接与 DGAT1 启动子中的 CE1 样元件（CACCG）结合。遗传研究还表明，abi4 突变体中的 TAG 积累和 DGAT1 表达减少。综上所述，我们的结果表明，脱落酸信号是调节 TAG 异位积累的调控机制的一部分，ABI4 是氮饥饿期间拟南芥幼苗中 DGAT1 激活所必需的。
