苎麻耐镉能力基因型差异的生理和分子机制

Cadmium (Cd) contamination is of considerable concern worldwide due to its potential toxicity to various organisms. The eco-restoration is the first step for the seriously contaminated region. The plant species with high tolerance to heavy metals could be qualified for the eco-restoration. Ramie (Boehmeria nivea), also named "China grass", is an important source of cellulose-rich natural fibres (bast fibres) which has rapid growth, higher biomass and rich genotypes. It is significative to renovate heavy metals from contaminated soil with ramie due to its high accumulation and high economic value. For the Cd contaminated land, culturing ramie is a candidate measure for safely reuse of the land, since ramie could minimizes the potential hazard of bringing toxic metals into food chains. There are some reports about the physiological and molecular characterization of accumulation in plants heavy metals stresses, however, absorption, chelation and transport processes have not been studied as a holistic approach. In this study, hydroponic culture experiment will be carried out to analysis growth and development of three ramie genotypes in Cd treatment. Meanwhile, physiological and molecular mechanism of Cd absorb,detoxification and translocate in ramie will be researched with the help of morphological,physiological and molecular technologies. These results could be provide theoretical basis both for increase Cd uptake ability of plants and phytoremediation or safely utilization of Cd contaminated land with ramie.

苎麻是中国特产的纤维用经济作物，生物量大，对重金属镉（Cd）具有较强的耐性和富集能力。苎麻作为纺织原料，进入食物链的风险小，是生物修复重金属污染土壤的潜力植物。研究苎麻耐镉能力基因型差异及其生理和分子机制将为充分发挥苎麻生态修复功能，应用分子生物学和基因工程调节植物富集重金属Cd能力提供理论基础。吸收、螯合和转运是植物耐受和积累重金属的主要原因, 目前揭示了植物富集重金属的部分机制，但吸收、螯合以及转运这一整套机制尚未进行整体的协同研究。本项目在前期筛选出高、中、低耐镉能力苎麻基因型的基础上，采用形态学、生理学及分子生物学技术方法，系统研究Cd胁迫下不同耐镉能力苎麻基因型生长和发育，阐明吸收、螯合和转运Cd生理和分子机制，探讨苎麻耐受和富集Cd的机理。

本项目在筛选出高、中、低耐Cd能力苎麻基因型的基础上，采用形态学、生理学及分子生物学技术方法，系统研究Cd胁迫下不同耐镉能力苎麻基因型的生长和发育，阐明吸收、螯合和转运Cd的生理和分子机制。结果表明低浓度镉对苎麻植株的生长有促进作用，但苎麻叶片净光合速率、胞间CO2浓度、气孔导度、蒸腾速率受镉抑制。测定苎麻不同部位金属硫蛋白MT，结果表明MT含量与部位和镉含量无显著相关。苎麻根系质膜H+-ATPase和Ca2+-ATPase活性随镉浓度逐步下降，不同耐性苎麻品种存在显著差异。.克隆了苎麻抗坏血酸过氧化物酶（BnAPX1）、谷胱甘肽还原酶（BnGR1）、植物螯合肽合成酶（BnPCS1）、转运ATP酶（BnHMA1）和BnATM1，对5个基因的表达特性进行了分析。组织特异性分析表明，苎麻BnAPX1、BnGR1、BnPCS1、BnHMA1、BnATM1基因在根、茎、茎尖、幼叶、成熟叶中均有表达，BnAPX1基因在幼叶中的表达量较高，茎中表达量最低；BnGR1基因在成熟叶中的表达量最高，在茎中表达量最低；BnPCS1基因在成熟叶中的表达量最高，茎中表达量最低，BnHMA在杆中的表达量最高，BnATM 在苎麻叶中表达量最高。BnAPX1、BnGR1、BnPCS1、BnHMA1、BnATM1基因均受Cd胁迫诱导上调表达。