miR159/167和ABC/NRAMP1转运蛋白调控油菜土壤镉低积累的机理与应用

Over-acumulation of Cd in soils is a threat to crop production and food safty. Although remediation strategy may reduce Cd concentrations in soils, the practically large-scale utility of the strategy is a time-consuming task. Recently, an alternative way has been proposed to limit heavy metals entering the food chain without treating soils. This concept concerns the technique to minimize toxic heavy metal accumulation in edible organs of crops. We recently isolated two metal transporter genes ABC/NRAMP1 from Cd-exposed Brassica napus. Interestingly, the ABC and NRAMP1 transcripts were identified as the targets of miR159 and miR167, respectively. In this project, we will functionally identify both ABC/NRAMP1 and miR159/167 by investigating ABC/NRAMP1 mediation of Cd uptake, translocation, and accumulation in tissues and oil seeds. Comparative study will be made on the Cd accumulation between low-accumulating and hyper-accumulating Brassica napus strains. Coordinated regulation of the processes by ABC/NRAMP1 and miR159/167 will be investigated under the field conditions. The aim of our proposal is to uncover the role of ABC/NRAMP1 in minimizing Cd uptake and accumulation in oil seeds of B. napus.

农田土壤中镉浓度超标影响我国农产品质量与安全。筛选Cd低积累作物品种，探明Cd低积累的调节机制，结合植物修复技术使作物籽粒中Cd含量低于食品安全标准是目前保障粮食安全生产的有效措施之一。本课题针对上述问题，将对一个Cd低积累的油菜品系中已筛选得到的受miR159/167负调控的二个金属转运蛋白基因ABC/NRAMP1进行功能鉴定。采用同位素109Cd示踪和原位非损伤技术研究miR159/167和ABC/NRAMP1调节油菜不同组织和器官内对Cd的吸收、转运和分配机制。比较研究油菜Cd低积累和高积累不同品种间miR159/167和ABC/NRAMP1基因和蛋白质差异表达模式与组织、籽粒中Cd积累之间的关系。在Cd污染农田土壤中，鉴定ABC/NRAMP1调节油菜不同品种秸秆及籽粒产品（油菜籽、菜籽油和菜籽饼等）中Cd的富集行为。上述研究结果可为育种筛选或培育Cd低积累的油菜品种提供理论基础。

农田土壤中镉浓度超标影响我国粮食生产和食品安全。通过各种修复技术能降低土壤中Cd的含量，但对轻中度污染的大面积土壤实施修复显然不符合实际。筛选和培育Cd等重金属低积累作物品种，使作物籽粒中重金属含量低于食品安全标准是目前一个切实可行的有效措施。本课题针对上述问题，从一个Cd低积累的甘蓝型油菜中筛选得到对Cd响应并受miR159/167沉默抑制调控的二个金属转运蛋白基因ABC/NRAMP1。本项目系统鉴定了这两个未知基因的金属转运功能。从64个不同基因型甘蓝型油菜中筛选得到两对Cd高积累和Cd低积累的品种，系统研究了这些品种不同组织器官（包括花、籽粒等）对Cd的积累效应。鉴定和研究了对Cd响应的ABC/NRAMP1等转运蛋白基因。通过基因组学筛选，发现和鉴定了miR167等在Cd胁迫下可以被长链非编码RNA所调控的可能机理，为深入揭示miRNAs及其靶基因调控油菜对Cd的积累机制提供了新思路和新方法，为进一步运用育种技术培育Cd低积累的油菜品种提供了理论依据。