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代谢和生产力有着深远的影响。低无机磷酸盐可利用性触发代谢反应以维持植物细胞内磷酸盐稳态。植物通过严格控制策略来应对外源磷限制，以重新确定代谢磷酸盐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。本项目致力于研究植物利用新型的卤酸脱卤酶（HAD）超家族磷酸酶在细胞内动员磷酸盐的功能策略。各自的基因在Pi饥饿中以高度特异性的方式上调。我们最近发现AtPECP1和AtPPsPase1分别是磷酸乙醇胺/磷酸胆碱和焦磷酸盐特异性磷酸酶，它们的酶学性质表明它们在脂质和碳水化合物代谢中起功能作用。这是提出的工作的目标，阐明基因产物如何有助于适应低磷有效性。将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注入不同浓度的Pi，记录其生理、形态和生化反应。脂质降解产物和不同初级中间体（如磷酸化糖和udp活化糖）模式的变化将使用基于质谱的方法进行定量分析。工程蛋白将在突变体互补试验中进行功能测试。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将用于描述Pi饥饿反应的调节因子的影响。启动子驱动的报告基因对AtPECP1和ATPPsPase1的时空表达旨在检测pi依赖的源-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.