课题组前期研究发现以耐盐南瓜作为砧木可以提高嫁接黄瓜的耐盐性，主要在于砧木根系具有较强的Na+蓄积和木质部卸载能力，南瓜HKT1基因（CmHKT1）组织定位于根系中柱细胞，受盐胁迫诱导上调表达，具有较强的Na+转运能力，推测其参与限制Na+由南瓜砧木向黄瓜接穗转运过程，但相关分子机制尚不明晰。本项目拟通过免疫组化技术明晰该基因在南瓜砧木根系和茎段具体定位情况；通过爪蟾卵母细胞电生理技术分析CmHKT1基因的离子转运特性；采用黄瓜遗传转化、正反嫁接技术明确CmHKT1基因在嫁接复合体中调控Na+转运的具体功能。在此基础上利用酵母杂交筛选互作蛋白及调控因子，解析CmHKT1基因在砧用南瓜中的调控机制。本课题完成后不仅可以揭示CmHKT1基因的功能及其在黄瓜/南瓜嫁接复合体中限制Na+长距离运输的分子机制，还有利于丰富园艺作物砧穗互作的基本理论，促进砧用南瓜耐盐基因挖掘和黄瓜嫁接耐盐栽培。

In our previous research work, we have found that the utilization of pumpkin as a rootstock improves salt tolerance of grafted cucumber, owing to pumpkin roots have strong Na+ accumulation and unloading capacity. Recently we have also found that CmHKT1 has Na+ transport activity in yeast and also was up-regulated expression in root stelar cell under salt treatment. So we speculated that CmHKT1 participation in the restricted Na+ loading into xylem process and protected cucumber scions leaves from salinity stress, but the exact regulation mechanism of this process is yet unclear. In this project we intends to study the exact tissue and cellular localization of CmHKT1 in root and rootstock stem tissues by utilizing immunohistochemical localization techniques. Then Xenopus laevis Oocytes electrophysiological technique, cucumber genectic transformation technology, and reciprocal grafting combinations strategy will be utilized to clearly understand the functions of CmHKT1. Finally, we will identify the regulatory factors and interaction proteins through the yeast one-hybrid and two-hybrid screening system to resolve its regulatory mechanism to limit Na+ transport in pumpkin grafted cucumber. The implementation of this project will not only reveal the CmHKT1 gene function and the molecular mechanisms of long distance transport of Na+ in grafted plants, but it will also promote salt resistance gene mining of pumpkin rootstock and the cultivation of grafted cucumber.