盐胁迫严重影响棉花的产量和品质，深入研究棉花盐害响应对于培育耐盐棉花具有重要意义。bZIP类转录因子在植物耐逆中起关键的作用，但其调控机制却知之甚少。GhbZIPX转录因子是我们通过转录组和大规模转基因实验获得的响应盐胁迫蛋白，过表达棉花耐盐性显著提高，盐害诱发早衰有效延缓；相反，干涉棉花盐敏感增强、衰老加速。进一步研究鉴定到4个GhbZIPX候选靶基因：GhZTG1-GhZTG4。此4个基因编码蛋白属于同一家族，表达均在GhbZIPX过表达棉花中上调，干涉棉花中下降。GhZTG启动子区均含有bZIP类蛋白结合元件，酵母实验中GhbZIPX可直接结合GhZTG启动子调控其表达，说明GhZTG可能是GhbZIPX直接调控的靶基因。本项目在此基础上，进一步在体内和体外确定GhbZIPX对GhZTG表达的直接调控，研究他们在盐胁迫响应和叶片衰老中的分子遗传机理，探索在提高棉花耐盐中的应用潜力。

Salt stress is a main limiting factor for cotton growth and productivity. Plants have well developed sophisticated signaling pathways i.e. receptors, secondary messengers, phytohormones, and signal transducers for their survival in salt stress. The response of plants against salt stress also required differential gene expression mainly regulated by transcription factors (TFs). The bZIP TFs are key components in controlling transcription initiation rates to modulate salt stress-associated genes expression for the salinity signal cascade transmission. However, its regulatory mechanism is poorly understood. Using RNA-sequencing analysis, large-scale gene expression and transgenic plant analyses, we obtained a novel member of cotton bZIP TF, named GhbZIPX. Overexpression of GhbZIPX significantly enhanced salt tolerance and produced a marked delay of salt-induced leaf senescence, whereas knockdown of GhbZIPX increased salt sensitivity and promoted senescence proceeding, confirming the role of GhbZIPX TF in the salt responsive of cotton. We further performed RNA-sequencing analysis on GhbZIPX-overexpression cottons and wild type. Strikingly, among 659 up-regulated genes with alteration of 2-fold or more, GhZTG1-GhZTG4 genes were up-regulated in ABA and salt treatment. Moreover, activated and repressed expressions of GhZTG1-GhZTG4 were observed in GhbZIPX overexpression and RNAi cottons, respectively. According to the AthaMap, the 2,000-bp GhZTG1-GhZTG4 promoter regions contain several A-box, C-box, or G-box motifs. Consistently, a yeast one-hybrid assay also showed that the GAL4 transcriptional activation domain-GhbZIPX (AD-GhbZIPX) fusion protein activated the LacZ reporter gene driven by the promoters of GhZTG1-GhZTG4. Taken together, we reasonably speculate that GhbZIPX act as a transcription factor to regulate the expression levels of GhZTG1-GhZTG4 by directly binding to their promoter region in vivo. In this proposed study, we would like to investigate the mechanism of GhbZTG1-GhZTG4 involved in salt stress response and leaf senescence by using genetics, molecular biology, and biochemistry means, and also explore its possible application in cotton salt tolerance improvement.