脂质是植物细胞的重要组分，它们是构成细胞膜的基础，为代谢活动提供能量和参与植物对逆境的响应。研究表明，甘油脂、脂肪酸和鞘脂等脂信号分子在植物响应冷冻、干旱和病原菌等逆境中起重要作用，但目前尚未知脂质是否参与植物对低氧胁迫的应答。前期研究显示，短期低氧处理显著诱导磷脂酰丝氨酸（PS）、磷脂酸（PA）和极长链脂肪酸（VLCFA）等含量的积累，而其他磷脂的含量则显著下降。同时，低氧下磷脂多不饱和酰基链含量明显增加，而其饱和及单不饱和链含量则减少。其中PA积累与磷脂PC和PE降解成正相关，而PS和VLCFA积累则与鞘脂的增加成正相关。表型分析显示，鞘脂和VLCFA合成途径中编码关键酶LOHs和LACSs等基因的突变体对低氧胁迫非常敏感。本项目拟通过分子生物学和生物化学等手段，深入解析鞘脂及角质层等VLCFA衍生物在调控植物响应低氧胁迫中的生理功能，及鞘脂介导的低氧反应与乙烯信号相互作用的分子机理。

Lipids are major and vital cellular components in plants. They provide structural basis for cell membranes and energy for metabolic processes, and are required for plant stress response. Recent investigations suggest than certain lipids such as glycerolipids, sphingolipids, oxylipins, fatty.acids and sterols, play essential roles as signaling messengers in plant response to cold, drought and pathogen infections. However, it is still unknown whether the lipid signaling involves in regulation of plant response to hypoxia, which stress requires extensive acclimated membrane.remodeling. Our preliminary data show that in Arabidopsis thaliana, a short-term hypoxic treatment induced a significant increase in the total amounts of phosphatidylserine (PS), phosphatidic acid (PA) as well as very-long-chain fatty acids (VLCFA), but a significant decrease in the total amounts of galactolipids and some species of phospholipids. Further, we observed that a significant increase in the polyunsaturated molecular species of phosphatidylcholine (PC), phosphatidyletanolamine (PE) and phosphatidylinositol (PI) and a decline in their saturated and.mono-unsaturated molecular species, suggesting that lipid desaturation occurs when the plants were exposed to hypoxia. The accumulated PA species were correlated with the declined species of PC and PE, while the highly accumulation of very-long-chain acyl chains of PS and VLCFA was accompanied with the increase of sphingolipids. Moreover, the knockout mutants of LOHs and LACSs, which encodes key enzymes required for sphingolipids and VLCFA biosynthesis, respectively, displayed more sensitive to hypoxic stress. The aim of this proposal is to investigate the essential roles of VLCFAs and their derivates including sphingolipids and cuticular lipid biosynthesis in regulating plant response to hypoxia. By molecular, genetics and biochemical approaches, we further intend to elucidate the mechanism of how sphingolipids interact with the ethylene signaling pathway to regulate hypoxia tolerance in plant.

脂质是植物细胞的重要组成部分，是构成细胞膜的基础，也为代谢活动提供能量及参与植物对逆境的响应。研究表明，甘油脂、脂肪酸和鞘脂等脂信号分子在植物响应冷冻、干旱和病原菌等逆境中起重要作用，但目前尚未知道脂质是否参与植物对低氧胁迫的应答。本项目首次结合脂质组学和功能基因组学技术，揭示模式植物拟南芥响应低氧胁迫过程中，各种脂质成分（包括膜磷脂、长链与极长链脂肪酸及其衍生物鞘脂等）的适应性变化和内在调整机制。通过基因芯片分析，获得低氧胁迫后野生型植物中脂质相关基因的表达谱，发现许多脂质合成及代谢相关基因的表达发生显著性变化。利用 ESI-MS/MS脂质分析技术，对野生型植株在低氧处理前后叶片中的膜磷脂、脂肪酸、鞘脂等成分进行详细的生化分析，发现脂质的去饱和作用、磷脂酸、极长链脂肪酸和鞘脂成分的积累等变化与植物低氧反应密切相关。通过低氧胁迫的耐受性表型和脂质组学分析，发现含极长链且不饱和的脂肪酸的神经酰胺含量变化可能是导致loh突变体在DS和LS处理后表型迥然不同的主要原因。体外重组蛋白与配体分子结合实验证明，神经酰胺与乙烯信号通路的负调控因子CTR1重组蛋白相互作用，阐明了其对乙烯信号通路的调控作用。遗传学分析进一步验证神经酰胺通过与CTR1 结合调控乙烯信号相关的低氧反应的分子机制。通过对ACBP3 参与植物响应低氧胁迫的功能分析发现，ACBP3可能参与抑制植物响应低氧过程中极长链脂肪酸和鞘脂的合成与代谢。采用微量热泳动仪技术，发现ACBP3 重组蛋白与极长链酰基-CoA在体外高亲和度相互作用，从分子水平揭示了ACBP3调控低氧下脂质成分变化可能是由于其与极长链酰基- CoA 相结合，并负调控其在植物细胞内的动态含量来实现的。这些发现为解析植物低氧感受和信号转导网络提供了重要线索和新的研究方向，对于理解植物应答低氧的分子机制具有重要的科学意义，同时也为耐涝作物遗传育种和分子设计提供了必要的理论基础和基因资源。