BACKGROUND Membrane lipid composition associates closely with membrane stability and fluidity under water stress. In this study, lipidomic analyses based on electrospray ionization mass spectrometry (ESI-MS/MS) were carried out to explore dynamic changes of membrane lipids in term of molecular species caused by PEG (Polyethylene glycol-6000)-induced water stress in wheat seedlings. RESULTS Among the main phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) are primary degradation targets, and PC was degraded in the largest degree. Membrane ion leakage dramatically increased later than the significant reduction of these phospholipids, indicating that the loss of membrane integrity lagged behind severe phospholipid degradation. Monogalactosyldiacylglycerol (MGDG) increased firstly and decreased later, while digalactosyldiacylglycerol (DGDG) ratcheted up with stress. DGDG/MGDG increased after stress for 3 days, and unsaturation of DGDG was promoted with stress. Variation trends of galactolipids differed among molecular species. The time when MGDG (34:3), DGDG (34:3) began to decline approached to the time when non-stomatal limitation impaired photosynthesis. While the two predominant molecular species MGDG (36:6) and DGDG (36:6) began to decline later. So we speculated that MGDG (34:3), DGDG (34:3) might be key components in photosynthesis apparatus and participate in photosynthesis directly. While the two predominant molecular species, MGDG (36:6) and DGDG (36:6) might locate in thylakoid lipid bilayer matrix and play roles in stabilizing the membrane. The research provides new insights into the dynamic response of lipid metabolism to PEG-induced water stress. CONCLUSION In wheat plants under water stress, the major molecular species of PC, PE and PG were degraded, MGDG and DGDG molecular species had differing degradation time courses.

中文翻译：

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PEG诱导的水分胁迫下冬小麦幼苗叶片膜脂成分的动态变化

背景技术膜脂质组合物与在水分胁迫下的膜稳定性和流动性紧密相关。本研究基于电喷雾电离质谱（ESI-MS / MS）进行了脂质组学分析，探讨了由PEG（Polyethyleneethylene-6000）引起的小麦幼苗水分胁迫引起的分子种类中膜脂的动态变化。 。结果在主要的磷脂中，磷脂酰胆碱（PC），磷脂酰乙醇胺（PE）和磷脂酰甘油（PG）是主要的降解目标，PC的降解程度最大。膜离子泄漏显着增加，晚于这些磷脂的显着减少，表明膜完整性的损失落后于严重的磷脂降解。单半乳糖基二酰基甘油（MGDG）首先增加，之后减少，而二半乳糖基二酰基甘油（DGDG）则因压力增加而棘手。应激3天后DGDG / MGDG升高，并且应激会促进DGDG的不饱和。半乳糖脂的变化趋势在分子种类之间是不同的。MGDG（34：3），DGDG（34：3）开始下降的时间接近非气孔限制损害光合作用的时间。两种主要的分子种类MGDG（36：6）和DGDG（36：6）随后开始下降。因此，我们推测MGDG（34：3），DGDG（34：3）可能是光合作用设备中的关键成分，并直接参与光合作用。MGDG（36：6）和DGDG（36：6）这两个主要分子种类可能位于类囊体脂质双层基质中，并在稳定膜中发挥作用。该研究为脂质代谢对PEG诱导的水分胁迫的动态响应提供了新的见解。结论在水分胁迫下的小麦植株中，PC，PE和PG的主要分子种类被降解，MGDG和DGDG的分子种类具有不同的降解时间进程。