Linking Calcium Sensor Gene Duplication and Functional Divergence to Plant Salt Tolerance

土壤盐碱化影响着全球6%以上的陆地面积，目前全球每分钟至少损失3公顷耕地。据估计，仅在美国，土壤盐分每年就会使灌溉作物的产量减少20-30%。除了少数例外，农作物无法适应土壤中盐含量升高所引起的压力。虽然植物生长的耐盐性存在遗传变异，但对这种变异的基因知之甚少。在植物Eutrema salsugineum中发现了两个拷贝的钙传感器基因，而许多相关物种只有一个拷贝。由于Eutrema能够在高盐土壤中生长，而高盐土壤会杀死大多数（如果不是所有的话）农作物，因此该基因的复制为将其功能与植物耐盐性联系起来提供了独特的机会。为此，该项目将揭示原始和复制基因的功能是如何以及何时分化的，并确定由此产生的生理变化。此外，该项目将通过对亚利桑那大学学生和博士后研究人员的继续教育和培训，为图森地区主要为少数民族服务的K-12教室设计简单的研究模块，以及参与对亚利桑那州南部K-12学生和社区的推广工作，来加强研究、培训和推广的基础设施。基因复制是遗传多样性的主要来源，因此也是适应性进化的主要来源。因为大多数复制基因都是通过假基因化而丢失的，所以基因组中复制基因对的维持可以表明同源基因赋予的适应性利益。CBL10钙传感器在盐敏感模式植物拟南芥（Arabidopsis thaliana）中作为单个基因存在，但在其耐盐亲缘植物Eutrema（均为芸苔科成员）中作为两个基因存在。该项目将利用为拟南芥开发的遗传和基因组资源来确定基因复制事件如何产生新的性状和表型，并有助于植物适应。具体来说，CBL10基因表达降低的Eutrema的表征将确定其在耐盐性中的特定功能（Aim 1）。对芸苔科近缘种CBL10同源物的功能分析将确定重复的Eutrema基因何时获得导致其功能分化的变化（Aim 2）。对CBL10蛋白序列和生化活性的分析将确定Eutrema CBL10功能差异和相关生理机制的结构域（Aim 3）。

Soil salinity affects over 6% of the world's land mass, and currently causes the loss of at least three hectares of arable land worldwide each minute. It has been estimated that, in the United States alone, soil salinity reduces irrigated crop yields by 20-30% annually. With few exceptions, crop plants are unable to adapt to the stresses induced by elevated levels of salt in the soil. While genetic variation for plant growth in salinity (salt tolerance) exists, little is known about the genes underlying this variation. Two copies of a calcium sensor gene has been found in the plant species Eutrema salsugineum, while many related species have only one copy. Because Eutrema is able to grow in high salt soils that kill most, if not all crop plants, the duplication of this gene provides a unique opportunity to link its function to plant salt tolerance. To do this, the project will uncover how and when the functions of the original and duplicate genes diverged and identify the physiological changes that resulted. In addition, this project will be used to enhance the infrastructure of research, training, and outreach through the continued education and training of students and postdoctoral researchers at the University of Arizona, design of simple research modules for largely minority-serving K-12 classrooms in the Tucson area, and participation in outreach efforts to K-12 students and the community in Southern Arizona.Gene duplication is a major source of genetic diversity and, consequently, adaptive evolution. Because most duplicated genes are lost via pseudogenization, the maintenance of duplicated gene pairs in a genome can be indicative of an adaptive benefit conferred by the paralogous genes. The CBL10 calcium sensor is present as a single gene in the salt-sensitive model plant Arabidopsis thaliana (Arabidopsis), but as two genes in its salt-tolerant relative, Eutrema (both members of the Brassicaceae). This project will use the genetic and genomic resources developed for Arabidopsis to determine how new traits and phenotypes emerge from a gene duplication event and contribute to plant adaptation. Specifically, characterization of Eutrema with reduced expression of the CBL10 genes will determine their specific functions in salt tolerance (Aim 1). Functional analysis of CBL10 homologs from closely related species within the Brassicaceae will determine when the duplicated Eutrema genes acquired the changes that led to their functional divergence (Aim 2). Analyses of CBL10 protein sequences and biochemical activities will identify domains that underlie the differences in Eutrema CBL10 function and the associated physiological mechanisms (Aim 3).