盐芥与拟南芥磷转运体基因家族表达调控与功能比较

Soil salinization and the resulting lack of available phosphorus have become a worldwide ecological problem that severely constrain agriculture production. It is the necessary basis to study the molecular mechanism of salt adaptation in halophytes for salt tolerant crop breeding and the ecosystem recovery of salinized wasteland. Understanding the regulatory mechanism of inorganic phosphate (Pi) uptake and utilization under salinity is the central issue to reveal the mechanism of salt tolerance as well as inorganic phosphate (Pi) uptake and utilization in plant. Plant phosphate transporters (PT) play an important role in phosphorus absorption and transport to maintain the dynamic equilibrium of the intracellular inorganic phosphorus. Thellungiella halophila, a close relative of Arabidopsis, is an extremophile native to harsh environments and can reproduce under extreme salinity and phosphorus deficiency. In this work, PT gene family of T. halophila and Arabidopsis will be investigated comparatively to understand the gene expression and regulation mechanism. Firstly, the gene copy number, gene structure, promoter structure, and transcriptional expression patterns of PT gene family in the two plants are analyzed comparatively to study the mechanism of molecular evolution under different environment, and further to find the specific promoters and genes in T. halophila. Then, the function of one or two specific promoters and PT genes in T. halophila will be studied through molecular genetical approach. The main purpose of this work is to reveal the mechanism of Pi uptake and utilization in T. halophila under salinity, then to make further effort on the regulation mechanism of plant Na+ and Pi, and finally to identify potential genes for genetic improvement of crops.

土壤盐渍化及其导致的有效磷不足已成为世界性的重大资源与生态问题。深入研究盐生植物的盐适应分子机制，是培育抗盐作物新品种，恢复和重建盐碱荒地生态系统的基础。研究盐对植物磷吸收利用的调控机制既是揭示植物抗盐机制的重要环节，也是植物磷吸收利用机制研究的重要方面。磷转运体（phosphate transporter, PT）在植物磷吸收及磷转运中发挥着重要作用。本工作以既抗盐又耐低磷的盐芥（Thellungiella halophila）为材料，首先从整体层面比较盐芥与拟南芥PT基因家族成员在拷贝数、基因结构、启动子结构以及表达模式方面的异同，研究不同生境下PT基因家族的分子进化特点，同时寻找盐芥特异启动子和特异基因；然后通过分子遗传学方法对其中的1-2个特异启动子和基因进行功能研究，以期揭示盐胁迫下盐芥磷高效吸收利用机制及Na+/Pi调控机制，并为作物的遗传改良挖掘潜力基因。

土壤盐渍化及其导致的有效磷不足已成为世界性的重大资源与生态问题。深入研究盐生植物的盐适应分子机制，是培育抗盐作物新品种，恢复和重建盐碱荒地生态系统的基础。研究盐对植物磷吸收利用的调控机制既是揭示植物抗盐机制的重要环节，也是植物磷吸收利用机制研究工作的重要方面。磷转运体（PT）在植物磷吸收及磷转运中发挥着重要作用。本项目通过分析比较盐芥与拟南芥4个PT基因家族的基因拷贝数、进化树特点、基因及蛋白结构，结合盐芥和拟南芥低磷条件下的生理指标分析，揭示了盐芥PHT1家族多个基因的串联重复在盐芥磷高效吸收中的重要作用。通过盐芥和拟南芥PT基因启动子结构与功能研究及PT基因在盐+低磷胁迫下的表达模式的差异分析，发现了若干盐胁迫下盐芥特异表达的PT基因包括ThPht1;5、ThPht1;9、ThPht2;1、ThPht4;2 和ThPht4;4等。接着，我们通过分子遗传学方法对其中的ThPht1;5和ThPht1;9基因的功能和调控因子进行了深入研究。利用获得的沉默和过表达转基因株系进行低磷和盐处理的生理生化指标测定，初步结果显示ThPht1;5和ThPht1;9在盐胁迫下的盐芥低磷响应中发挥重要作用，该项目获得的这些遗传材料为进一步研究ThPht1;5和ThPht1;9作用机理奠定了基础。同时，通过对ThPht1;5和ThPht1;9启动子进行分析检测，预测了多个调控ThPht1;5和ThPht1;9表达的转录因子，并通过酵母单杂交方法鉴定到了三个转录因子，初步揭示了盐芥盐胁迫下磷高效吸收利用机理。以上研究为抗盐、耐低磷作物的遗传改良提供了潜力基因资源，为深入揭示植物在盐胁迫下磷吸收利用机制奠定了良好的基础。