Mechanism for Membrane Lipid Alteration upon Phosphate Starvation in Plants

植物磷酸盐饥饿时膜脂改变的机制

• 批准号: 15380049
• 负责人: OHTA Hiroyuki
• 金额: $ 8.13万
• 依托单位: Tokyo Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15380049/
• 关键词: Phosphate starvation; Galactolipids; Phospholipids; Glycosyltransferase; Phospholipase C; Membrane lipids; ホスホリパーゼ

1. Galactolipid synthesis under phosphate starvationDuring phosphate (Pi) starvation in plants, membrane phospholipid content decreases concomitantly with an increase in non-phosphorus glycolipids. Although several studies have indicated the involvement of phytohormones in various physiological changes upon Pi starvation, the regulation of Pi-starvation induced membrane lipid alteration remains unknown. Previously, we reported the response of type B monogalactosyl diacylglycerol synthase genes (atMGD2 and atMGD3) to Pi starvation, and suggested a role for these genes in galactolipid accumulation during Pi starvation. In this project, we performed an investigation of the regulatory mechanism for the response of atMGD2/3 and changes in membrane lipid composition to Pi starvation. Exogenous auxin activated atMGD2/3 expression during Pi starvation, whereas their expression was repressed by cytokinin treatment in the root. Moreover, auxin inhibitors and the axr4 aux1 double mutation in auxi … More n signaling impaired the increase of atMGD2/3 expression during Pi starvation, showing that auxin is required for atMGD2/3 activation. The fact that hormonal effects during Pi starvation were also observed with regard to changes in membrane lipid composition demonstrates that both auxin and cytokinin are indeed involved in the dynamic changes in membrane lipids during Pi starvation. Phosphite is not metabolically available in plants ; however, when we supplied phosphite to Pi-starved plants, the Pi-starvation response disappeared with respect to both atMGD2/3 expression and changes in membrane lipids. These results indicate that the observed global change in plant membranes during Pi starvation is not caused by Pi-starvation induced damage in plant cells but rather is strictly regulated by Pi signaling and auxin/cytokinin cross-talk.2. Phospholipid catabolism upon phosphate starvationDuring phosphate starvation, it is known that phospholipids are degraded, and conversely, a non-phosphorus galactolipid digalactosyldiacylglycerol accumulates in the root plasma membrane of plants. In this project, we found on a novel phospholipase C which hydrolyzes phosphatidylcholine and is greatly induced in response to phosphate deprivation in Arabidopsis. Since phosphatidylcholine-hydrolyzing activity by phospholipase C was highly up-regulated in phosphate-deprived plants, gene expression of some phospholipase C was expected to be induced during phosphate starvation. Based on amino acid sequence similarity to a bacterial phosphatidylcholine-hydrolyzing phospholipase C, six putative phospholipase Cs were identified in the Arabidopsis genome, one of which, NPC4, showed significant transcriptional activation upon phosphate limitation. Molecular cloning and functional expression of NPC4 confirmed that NPC4 gene encoded a functional phosphatidylcholine-hydrolyzing phospholipase C which did not require Ca^<2+> for its activity. Subcellular localization analysis showed that NPC4 protein was highly enriched in the plasma membrane. Analyses of T-DNA tagged npc4 mutants revealed that disruption of NPC4 severely reduces the phosphatidylcholine-hydrolyzing phospholipase C activity in response to phosphate starvation. These results suggest that NPC4 plays an important role in the supply of both inorganic phosphate and diacylglycerol from membrane-localized phospholipids that would be used for phosphate supplementation and the replacement of polar lipids in the root plasma membrane during phosphate deprivation. Less

1.磷饥饿条件下半乳糖脂的合成在植物磷（Pi）饥饿期间，膜磷脂含量减少，同时非磷糖脂增加。虽然一些研究表明，植物激素参与各种生理变化后，磷饥饿，磷饥饿诱导的膜脂变化的调节仍然是未知的。以前，我们报道了响应B型单半乳糖基二酰基甘油合酶基因（atMGD 2和atMGD 3）的Pi饥饿，并建议这些基因在半乳糖脂积累在Pi饥饿的作用。在这个项目中，我们进行了调查的调节机制的atMGD 2/3和膜脂组成的变化，以磷饥饿的反应。外源生长素激活atMGD 2/3表达在磷饥饿期间，而他们的表达被抑制细胞分裂素处理的根。此外，生长素抑制剂和axr 4 aux 1双突变在auxi ...更多信息 在磷饥饿过程中，生长素信号减弱了atMGD 2/3表达的增加，表明atMGD 2/3的激活需要生长素。事实上，激素的影响，在磷饥饿期间也观察到膜脂组成的变化方面，表明生长素和细胞分裂素确实参与了磷饥饿期间膜脂的动态变化。亚磷酸盐在植物中是不能代谢的;然而，当我们向Pi饥饿的植物提供亚磷酸盐时，相对于atMGD 2/3表达和膜脂质的变化，Pi饥饿反应消失。这些结果表明，在磷饥饿过程中所观察到的植物膜的整体变化不是由磷饥饿诱导的植物细胞损伤引起的，而是受磷信号和生长素/细胞分裂素串扰的严格调控。在磷酸盐饥饿期间，已知磷脂被降解，并且相反地，非磷半乳糖脂二半乳糖基二酰基甘油在植物的根质膜中积累。在本项目中，我们发现了一种新的磷脂酶C，它水解磷脂酰胆碱，并在拟南芥中对磷酸盐剥夺的反应中被极大地诱导。由于磷脂酶C的磷脂酰胆碱水解活性在缺磷植物中高度上调，因此在磷饥饿期间，一些磷脂酶C的基因表达有望被诱导。基于氨基酸序列的相似性，细菌磷脂酰胆碱水解磷脂酶C，6个假定的磷脂酶C被确定在拟南芥基因组中，其中之一，NPC 4，磷酸限制后，表现出显着的转录激活。NPC 4基因的克隆和功能表达证实NPC 4基因编码一种功能性的磷脂酰胆碱水解磷脂酶C，其活性不需要Ca^2+。亚细胞定位分析表明，NPC 4蛋白高度富集在质膜上。T-DNA标记的npc 4突变体的分析表明，NPC 4的破坏严重降低了响应磷酸盐饥饿的磷脂酰胆碱水解磷脂酶C的活性。这些结果表明，NPC 4起着重要的作用，在供应无机磷酸盐和甘油二酯从膜定位的磷脂，将用于磷酸盐补充和极性脂质的替代在根质膜在磷酸盐剥夺。少

项目成果

Koichi Kobayashi, Koichiro Awai, Ken-ichiro Takamiya, Hiroyuki Ohta: "Arabidopsis TypeB Monogalactosyldiacylglycerol Synthase Genes Are Expressed during Pollen Tube Growth and Induced by Phosphate Starvation"Plant Physiology. Vol.134. 640-648 (2004)

Koichi Kobayashi、Koichiro Awai、Ken-ichiro Takamiya、Hiroyuki Ohta：“拟南芥 B 型单半乳糖二酰基甘油合酶基因在花粉管生长期间表达并由磷酸盐饥饿诱导”植物生理学。

Metabolic changes of membrane lipid biosynthesis under phosphate starvation and its regulation by phytohormones

磷酸盐饥饿下膜脂生物合成的代谢变化及其植物激素的调控

• 发表时间: 2004
• 期刊: Nougei Kagaku Kai-shi 78,10
• 作者: Koichi Kobayashi;Hiroyuki Ohta
• 通讯作者: Hiroyuki Ohta

リン酸欠乏時における膜脂質合成系の代謝変動と植物ホルモンによる制御

缺磷期间膜脂合成系统的代谢变化及植物激素的控制

• 发表时间: 2004
• 期刊: 日本農芸化学会誌 78
• 作者: 小林康一;太田啓之
• 通讯作者: 太田啓之

Three enzyme systems for galactoglycerolipid biosynthesise are coordinately regulated in plants.

植物中半乳糖甘油脂生物合成的三种酶系统受到协调调节。

• 发表时间: 2005
• 期刊: J.Biol.Chem. 280・4
• 作者: C.Benning;H.Ohta
• 通讯作者: H.Ohta

山領和紀, 太田啓之: "高等植物のグリセロ糖脂質の生合成を担う糖転移酵素とその多様な機能"酵素工学ニュース. 50. 38-50 (2003)

Kazunori Yamaryo、Hiroyuki Ota：“糖基转移酶负责高等植物中甘油糖脂的生物合成及其多种功能”《酶工程新闻》50. 38-50 (2003)。