甜菜是一种抗逆性较强的嗜钠作物，以往有关Na+对甜菜有益作用的研究多集中在生长和耐盐性上，而我们最近发现Na+在甜菜响应干旱胁迫过程中也发挥着重要作用；液泡膜Na+/H+逆向转运蛋白(NHX)是介导液泡Na+区域化的重要功能蛋白，但其在甜菜抗旱性中的作用机理尚不清楚。本项目拟在前期工作基础上，通过系统分析渗透胁迫下2个抗旱性不同的甜菜品种根和叶细胞中Na+微区分布，探明甜菜Na+区域化与抗旱性的关系；克隆甜菜NHX蛋白基因BvNHX，采用Real-time PCR技术分析该基因在渗透胁迫下的转录丰度，通过在抗旱性强的品种中沉默BvNHX基因的表达、在抗旱性弱的品种中超表达该基因，分析沉默植株和超表达植株Na+微区分布及抗旱性的变化。以期揭示Na+在甜菜适应干旱中的作用机理，为阐明嗜钠作物逆境适应机制奠定理论基础。对我国北方地区农作物的抗逆性遗传改良和生态环境建设具有重要理论意义和实践价值。

Sugar beet (Beta vulgaris L.) is considered as a natrophilic crop with the stronger resistance to adverse environment. Researches on beneficial effects of Na+ in sugar beet were limited mainly the growth and salt tolerance, however, our recent studies showed that Na+ also plays very important roles in the response of sugar beet plants to drought stress. Tonoplast Na+/H+ antiporter (NHX) proved to be involved in the compartmentation of Na+ into vacuoles from cytosol. However, the precise mechanisms underlying this transporter in drought tolerance of sugar beet remained unclear. This project, based on our previous studies, will analyze the intracellular micro-distribution of Na+ in both root and shoot of two sugar beet cultivars with differing drought tolerance under osmotic stress, to investigate relationship between Na+ compartmentation and drought tolerance. BvNHX gene encoding tonoplast Na+/H+ antiporter will be cloned and characterized in sugar beet; the transcript abundance of this gene will be quantitatively analyzed by using real-time PCR in two cultivars exposed to osmotic stress; BvNHX gene in drought-resistance cultivar will be silenced by RNA interference method, and this gene will also overexpressed in drought-sensitive one, then cellular micro-distribution of Na+ and the changes of drought tolerance will be tested in both BvNHX-silenced plants and BvNHX-overexpressed plants, respectively. Results of this project may reveal the mechanisms underlying Na+ in adaptation of sugar beet to drought, and also should provide the theoretical basis for elucidating adaptative mechanisms of natrophilic crops to adverse environment. Overall, this project has the important theory significance and the practice value for the genetic improvement of crops and protection of ecological environment in arid and semi-arid regions in North China.