Institute for Botany and Molecular Genetics, RWTH Aachen University, Worringer Weg 3, D-52074 Aachen, Germany.
Institute for Botany and Molecular Genetics, RWTH Aachen University, Worringer Weg 3, D-52074 Aachen, Germany.
Biochim Biophys Acta Mol Cell Biol Lipids. 2020 Sep;1865(9):158763. doi: 10.1016/j.bbalip.2020.158763. Epub 2020 Jul 6.
Plants have evolved various acclimation responses to cope with phosphate depletion, including several changes in lipid metabolism. Thereby membrane phospholipids are dephosphorylated and can be used as an internal phosphate source, while galactolipids are incorporated into the membrane to maintain membrane functionality. Still little is known about the lipidomic and transcriptomic response of plants other than Arabidopsis thaliana upon phosphate starvation. Therefore, we employed lipidomics and transcriptomics to characterize the phosphate starvation response of lipid metabolism in tomato leaves and roots. Overall, phospholipid levels decreased and galactolipids increased during the acclimation response. In addition, an early increase of triacylglycerol was observed. Interestingly, there were major differences in the acclimation response of tomato leaves and roots: leaves mainly accumulated polyunsaturated triacylglycerol, while roots showed a massive increase in galactolipid content. In line with these results, we observed transcriptional induction of phospholipid degradation and galactolipid synthesis pathways in both analyzed tissues. In contrast, other aspects of the transcriptional response, in particular, the induction of phospholipid degradation, ER-localized fatty acid desaturation and triacylglycerol assembly differed between tomato leaves and roots. These results suggest a different modulation of degraded phospholipids toward triacylglycerols and galactolipids in phosphate-starved tomato leaves and roots. Possibly the availability and composition of acyl-CoA pools and ER-derived precursors trigger the synthesis of triacylglycerols or galactolipids. As the mechanism of triacylglycerol accumulation is poorly characterized outside of seed oil formation, these findings enhance our understanding of the phosphate starvation response and of how storage lipids accumulate under stress in vegetative tissue.
植物已经进化出各种适应反应来应对磷饥饿，包括脂质代谢的几种变化。由此，膜磷脂去磷酸化并可用作内部磷源，而半乳糖脂则被并入膜中以维持膜功能。除了拟南芥以外，其他植物在磷饥饿时的脂质组学和转录组学反应仍知之甚少。因此，我们采用脂质组学和转录组学来描述番茄叶片和根系在磷饥饿时的脂质代谢适应反应。总的来说，在适应反应过程中，磷脂水平下降，半乳糖脂增加。此外，还观察到三酰甘油的早期增加。有趣的是，番茄叶片和根系的适应反应存在重大差异：叶片主要积累多不饱和三酰甘油，而根部半乳糖脂含量大量增加。与这些结果一致，我们观察到在这两种分析组织中，磷脂降解和半乳糖脂合成途径的转录诱导。相比之下，转录反应的其他方面，特别是磷脂降解、内质网定位的脂肪酸去饱和和三酰甘油组装的诱导，在番茄叶片和根系之间存在差异。这些结果表明，在磷饥饿的番茄叶片和根系中，降解的磷脂向三酰甘油和半乳糖脂的转化受到不同的调节。可能酰基辅酶 A 池和内质网衍生前体的可用性和组成触发了三酰甘油或半乳糖脂的合成。由于三酰甘油积累的机制在种子油形成之外的研究中还不太清楚，这些发现增强了我们对磷饥饿反应的理解，以及在应激条件下如何在营养组织中积累储存脂质。
