Zhou Xue-Rong, Bhandari Sajina, Johnson Brandon S, Kotapati Hari Kiran, Allen Doug K, Vanhercke Thomas, Bates Philip D
Commonwealth Scientific and Industrial Research Organisation (CSIRO) Agriculture and Food, Canberra, Australian Capital Territory 2601, Australia.
Washington State University, Pullman, Washington 99164-6340.
Plant Physiol. 2020 Feb;182(2):739-755. doi: 10.1104/pp.19.00667. Epub 2019 Dec 2.
The triacylglycerols (TAGs; i.e. oils) that accumulate in plants represent the most energy-dense form of biological carbon storage, and are used for food, fuels, and chemicals. The increasing human population and decreasing amount of arable land have amplified the need to produce plant oil more efficiently. Engineering plants to accumulate oils in vegetative tissues is a novel strategy, because most plants only accumulate large amounts of lipids in the seeds. Recently, tobacco () leaves were engineered to accumulate oil at 15% of dry weight due to a push (increased fatty acid synthesis)-and-pull (increased final step of TAG biosynthesis) engineering strategy. However, to accumulate both TAG and essential membrane lipids, fatty acid flux through nonengineered reactions of the endogenous metabolic network must also adapt, which is not evident from total oil analysis. To increase our understanding of endogenous leaf lipid metabolism and its ability to adapt to metabolic engineering, we utilized a series of in vitro and in vivo experiments to characterize the path of acyl flux in wild-type and transgenic oil-accumulating tobacco leaves. Acyl flux around the phosphatidylcholine acyl editing cycle was the largest acyl flux reaction in wild-type and engineered tobacco leaves. In oil-accumulating leaves, acyl flux into the eukaryotic pathway of glycerolipid assembly was enhanced at the expense of the prokaryotic pathway. However, a direct Kennedy pathway of TAG biosynthesis was not detected, as acyl flux through phosphatidylcholine preceded the incorporation into TAG. These results provide insight into the plasticity and control of acyl lipid metabolism in leaves.
植物中积累的三酰甘油（TAGs，即油脂）是生物碳储存中能量密度最高的形式，被用于食品、燃料和化学品。人口增长和可耕地减少加剧了更高效生产植物油的需求。对植物进行工程改造，使其在营养组织中积累油脂是一种新策略，因为大多数植物仅在种子中积累大量脂质。最近，通过推动（增加脂肪酸合成）和拉动（增加TAG生物合成的最后一步）工程策略，烟草叶片被改造为能积累占干重15%的油脂。然而，要同时积累TAG和必需的膜脂，内源性代谢网络中未经改造反应的脂肪酸通量也必须进行调整，而这在总油脂分析中并不明显。为了增进我们对叶片内源性脂质代谢及其适应代谢工程能力的理解，我们利用了一系列体外和体内实验来表征野生型和转基因油脂积累烟草叶片中的酰基通量路径。在野生型和改造后的烟草叶片中，磷脂酰胆碱酰基编辑循环周围的酰基通量是最大的酰基通量反应。在油脂积累叶片中，进入甘油olipid组装真核途径的酰基通量增加，而以原核途径为代价。然而，未检测到TAG生物合成的直接肯尼迪途径，因为通过磷脂酰胆碱的酰基通量先于其掺入TAG。这些结果为叶片中酰基脂质代谢的可塑性和调控提供了见解。
