Metabolic adaptation of phosphate-starved plants - Functional analyses of novel-type, intracellular phosphatases of the the HAD superfamily

磷的有效性对植物的新陈代谢和生产力有着深远的影响。低无机磷可获得性触发代谢反应以维持植物细胞内磷的动态平衡。植物通过严格控制的策略来响应外源磷的限制，以重新确定代谢磷消耗和再动员途径的优先顺序，并最大限度地从环境中获取磷。本项目致力于研究卤酸脱卤酶(HAD)超家族中新型磷酸酶激活细胞内磷的功能植物策略。PI饥饿以一种高度特异的方式上调了各自的基因。我们最近发现的AtPECP1和AtPPsPase1的酶性质分别是磷乙醇胺/磷胆碱和焦磷酸专一性磷酸酶，这表明它们在脂肪和碳水化合物代谢中具有功能作用。这项拟议工作的目标是阐明基因产物如何促进对低磷供应的适应性反应。向酶功能完全受损或增强的拟南芥野生型植株和转基因品系提供不同浓度的磷，并记录生理、形态和生化反应。脂类降解产物和不同的初级中间体，如磷酸化和UDP活化的糖的模式的变化将使用基于质谱学的方法进行定量分析。这些工程蛋白将在突变互补分析中进行功能测试。由AtPPsPase1作用引发的营养应激诱导的转录变化将通过微阵列方法进行研究。定量RT-PCR将被用来描绘PI饥饿反应的调节因素的影响。由启动子驱动的报告基因AtPECP1和ATPPsPase1的时空表达旨在测试依赖PI的源-库关系。

The availability of phosphorus (P) has a profound impact on plant metabolism and productivity. Low inorganic phosphate availability triggers metabolic responses to maintain intracellular phosphate homeostasis in plants. Plants respond to exogenous P limitation with tightly controlled strategies to reprioritize metabolic phosphate consumption and remobilization pathways and to maximize the acquisition from the environment. This project is dedicated to functional plant strategies of intracellular phosphate mobilization by novel-type phosphatases which belong to the Haloacid Dehalogenase (HAD) superfamily. The respective genes are up-regulated by Pi starvation in a highly specific manner. Our recent discovery of the enzymatic properties of AtPECP1 and AtPPsPase1 which are phosphoethanolamine/phosphocholine and pyrophosphate-specific phosphatases, respectively, suggests functional roles in lipid and carbohydrate metabolism. It is the goal of the proposed work to elucidate how the gene products contribute to acclimatory responses to low P availability. Arabidopsis wild-type plants and transgenic lines completely compromised or enhanced in enzyme function will be supplied with different Pi concentrations and physiological, morphological and biochemical responses will be recorded. Changes in the pattern of lipid degradation products and distinct primary intermediates such as phosphorylated and UDP-activated sugars will be analyzed quantitatively using methods based on mass spectrometry. The engineered proteins will be tested for functionality in mutant complementation assays. Nutritional stress-induced transcriptional changes triggered by AtPPsPase1 action will be investigated by a microarray approach. Quantitative RT-PCR will be used to delineate the impact of regulatory factors of the Pi starvation response. The spatio-temporal expression of AtPECP1 and ATPPsPase1 by promoter-driven reporter genes are directed at testing Pi-dependent source-sink-relations.