SeXTH1在盐生植物盐角草组织肉质化形成中的功能研究

Tissue succulence is an important strategy for xerophytic and halophytic species to adapt to the drought and salt environment. However, the molecular mechanism of tissue succulence in plants is unclear. Xyloglucan endotransglucosylase/hydrolases (XTHs) are proposed to be a vital factor in tissue succulence. The relationship between XTHs and tissue succulence was only reported in plants without higher tissue succulence, for example Populus euphratica. In this project, using the typical stem-succulent halophyte Salicornia europaea as material, the following experiments would be done: observing the anatomy changes and tissue succulence in different organs under various NaCl conditions; cloning the sequence of SeXTH1 which is induced significantly by salt; quantitative analyzing transcript abundance of SeXTH1 in different organs under various NaCl conditions using real-time RT-PCR technique; evaluating the salt tolerance of plants, after gene silencing of SeXTH1 using RNA interference (RNAi), besides, tissue succulence, net photosynthetic rate, anatomy changes, shoot water-retaining capacity, Na+, K+ contents and distribution will be measured in SeXTH1-RNAi plants and wildtype. The results will help to analyze the function of SeXTH1 in tissue succulence and salt tolerance in S. europaea, also could provide theoretical basis and stress-resistant gene(s) for the genetic improvement of salt resistance in high quality forages and crops.

组织肉质化是众多旱生或盐生植物适应干旱和盐渍生境的重要生存策略之一，但其发生的分子机制尚不清晰。已有研究表明，木葡聚糖内转糖苷酶/水解酶(XTHs)可能参与盐诱导植物组织肉质化的发生，目前，仅在胡杨等组织肉质化并不发达的植物中有所报道。因此，本项目拟以茎高度肉质化的盐生植物盐角草为材料，观察盐处理下地上部的解剖结构变化并测定肉质化程度，克隆SeXTHs家族中受盐诱导最强烈的SeXTH1基因cDNA序列，分析其在盐角草根和地上部中的表达模式及和肉质化程度之间的相关性；通过RNAi技术沉默SeXTH1的表达，评价RNAi株系的抗盐性，观察盐处理下各植株的地上部解剖结构、并测定肉质化程度、净光合速率、地上部保水能力、Na+、K+的含量及微区分布。以期揭示SeXTH1在盐角草茎肉质化发生中的作用及对耐盐性的影响，为优良牧草及农作物耐盐性的遗传改良提供理论依据和抗逆基因资源。

本项目取得了以下主要进展和成果：（1）一定浓度NaCl（50-200 mM）能促进盐角草生长，在积累大量Na+的同时，体内能维持高浓度的K+含量；（2）盐角草的肉质化程度受盐强烈诱导，且在100 mM NaCl处理下达到最大；（3）盐胁迫下，盐角草通过改变表皮、角质层的厚度，增加贮水组织和导管的数量，从而增强输水能力，引起器官肉质化程度增加；（4）利用PacBio测序平台测定了盐角草的转录组，筛选到SeXTH家族成员35个，确定了受盐诱导最为强烈的SeXTH23，完成SeXTH23的克隆、鉴定和生物信息学分析；（5）将SeXTH23在烟草表皮细胞中瞬时表达，发现SeXTH23定位于内质网；（6）构建SeXTH23超表达载体，发现SeXTH23的超表达能促进杨树717的生长，且能显著提高它的耐盐性；（7）构建了SeXTH23的VIGS侵染载体，尝试了第一次侵染；（8）构建了SeXTH23的RNAi干扰载体，正在开展盐角草的遗传转化。本项目发表SCI二区论文1篇、中文核心期刊论文1篇、授权发明专利1项、联合培养硕士研究生2名（在读）。