托鲁巴姆重金属转运蛋白StZIP5和StZIP11基因调控植物对Cd累积的功能研究

Solanum torvum is a typical low Cd accumulation plant species and a ideal plant material for studying the molecular mechanisms of low Cd accumulation in plants. Cd content in the fruits of eggplant grafted onto S. torvum grown in Cd-polluted soils were found to be 75 % lower than those of ungrafted eggplants. However, the regulatory mechanisms of low Cd accumulation in S. torvum were largely unknown. In previous study, we identified two ZIP subfamily transporters StZIP5 and StZIP11 that were significantly been induced by Cd in S. torvum roots. Prelimilary study implied that the two genes were involved in low Cd accumulation in S. torvum. This project will analyze the underlying physiological and molecular mechanisms of StZIP5 and StZIP11 in modulating low Cd accumulation in S. torvum, including subcellular localization and tissue-specific expression analysis; plant growth and Cd content in overexpressing or RNAi transgenic plants; the comparative analysis of the function of ZIP5 and ZIP11 in S. torvum and S. melongena; and the mutagenic study identifying critical residues for the structure and function of StZIP5 and StZIP11. The yeast expression system was also used to confirm the gene function. This study is helpful for the breeding and cultivation of low Cd vegetable cultivars.

托鲁巴姆是一种镉 (Cd)低累积植物。以其作砧木嫁接茄子，可将茄子果实中Cd含量降低75%左右。但其Cd低累积的分子机理尚不清楚。前期我们采用深度测序，鉴定到2个在根部显著受Cd诱导的ZIP转运蛋白StZIP5和StZIP11。初步分析表明这2个基因参与调控了Cd在托鲁巴姆地上部的低累积过程。在此基础上，本项目拟开展StZIP5和StZIP11调控Cd低累积机理研究，包括亚细胞定位和组织特异性表达分析；构建各种过表达和抑制表达的转基因株系，分析植株生长和Cd含量，确定它们在调控Cd低累积中的功能；比较它们与茄子SmZIP5和SmZIP11功能差异；通过定点突变及随机突变，寻找可能参与调控托鲁巴姆Cd低积累的关键氨基酸残基，为改造ZIP家族成员离子选择性提供理论基础；并通过酵母表达体系验证其功能。本研究将为培育重金属低累积蔬菜作物育种提供理论依据。

托鲁巴姆是一种镉 (Cd)低累积植物。以其作砧木，可将茄子果实中Cd含量降低75%左右。但其Cd低累积的分子机理尚不清楚。前期我们采用深度测序，鉴定到2个在根部显著受Cd诱导的ZIP转运蛋白StZIP5和StZIP11。初步分析表明这2个基因参与调控了Cd在托鲁巴姆地上部的低累积过程。在此基础上，本项目构建了各种植物表达载体，对转基因植株的表型分析发现，过表达StZIP11的转基因植株幼苗叶片中Cd累积水平低于野生型对照，表明StZIP11参与了Cd在托鲁巴姆地上部的累积与分配。托鲁巴姆StZIP5或StZIP11基因在拟南芥中的过量表达增强了Zn和Cd毒害对拟南芥主根生长的抑制作用，表明该基因在拟南芥和托鲁巴姆中具有功能差异。但其中详细的分子机制，尚有待今后的进一步深入研究。在酵母中的表达分析研究还发现，StZIP5/11的过表达增强了酵母细胞对Cd毒害的敏感性。但酵母细胞Cd含量并无显著差异。本项目研究还采用深度测序鉴定了托鲁巴姆根中Cd毒害下差异表达的miRNA。这些研究结果将为培育重金属低累积蔬菜作物育种提供理论依据。