耐盐南瓜砧木嫁接是提高黄瓜耐盐性的有效措施。项目组前期研究发现，其根本原因在于南瓜砧木嫁接限制了Na+ 向黄瓜接穗的运输，但深入的作用机制尚不明晰。本项目拟以耐盐性强的南瓜和耐盐性弱的黄瓜为材料，自嫁及正反嫁接构建4种砧穗组合。通过X射线微区分析、激光扫描共聚焦显微镜等技术，研究NaCl胁迫下根系细胞和亚细胞水平Na+分布，明确南瓜砧木嫁接限制Na+ 向接穗运输的细胞学途径；利用qRT- PCR、原位杂交等技术，分析Na+转运蛋白基因NHX/HKT/SOS1的表达模式，获得南瓜砧木根系嫁接限制Na+向黄瓜接穗运输的关键基因；利用高通量测序和生物信息学等手段，研究NaCl胁迫下不同砧穗组合miRNA的差异，对miRNA靶基因进行注释和表达分析，鉴定出与砧穗Na+运输密切相关的miRNA。本课题完成后可为耐盐南瓜砧木嫁接提高黄瓜耐盐性提供理论依据，促进黄瓜的嫁接栽培。

Using salt-tolerant pumpkin as rootstock is an effective way to increase the salt tolerance of cucumber. Our previous results demonstrated that limiting Na+ transport to the cucumber by grafting onto salt-tolerant pumpkin rootstock under NaCl stress is the key reason. However, the underlying mechanism remains unclear. In this project, the salt-tolerant pumpkin and salt-sensitive cucumber will be used to obtain four grafting combinations: self-grafted cucumber and pumpkin, cucumber grafted onto pumpkin, and pumpkin grafted onto cucumber. The cellular pathway for limiting Na+ transport by the pumpkin rootstock to the cucumber scion will be studied through the investigation of cellular and subcellular Na+ distribution by X-ray microanalysis, laser scanning confocal microscope and so on. In addition, the key Na+ transporter genes will be identified through NHX/HKT/SOS1 gene expression pattern by the qRT- PCR and in situ hybridization. Finally, the miRNAs closely related with Na+ transport between rootstock and scion will be identified through the investigation of difference in miRNA, miRNA target prediction and expression between four grafting combinations using the techniques of high-throughput sequencing, bioinformatics and so on. The implementation of this project will provide cellular and molecular evidence for the improved salt tolerance of cucumber grafted onto salt-tolerant pumpkin rootstocks, and will promote the cultivation of grafted cucumber.