农田土壤中镉（Cd）浓度超标严重影响我国水稻生产与粮食安全。本课题将对一个水稻品系中筛选得到两个对Cd高度专一的金属转运体HMT及CTF进行功能鉴定与调控机理研究。通过遗传转化及突变体鉴定HMT和CTF参与调节水稻植株对Cd的吸收、积累与脱毒效应，研究两者调节Cd在水稻不同组织和器官内对Cd转运与分配的模式。在Cd污染农田土壤中，鉴定HMT和CTF调节水稻秸秆及籽粒中Cd的富集行为。由于前期研究发现Cd暴露能改变HMT和CTF基因甲基化水平及转录表达，项目将系统研究HMT和CTF基因 DNA甲基化与去甲基化模式、基因表达及Cd吸收、积累之间的关系。项目最终将阐明HMT和CTF参与水稻对Cd吸收、积累和脱毒作用，以及DNA甲基化参与调控HMT和CTF功能的分子机理。

Overacumulation of Cd in soils is a threat to rice production and food safty. Elucidation of regulatory mechanism for Cd uptake and accumulation in rice crops is critical to ensure the crop production and food safety. We recently isolated two metal transporter genes HMT (heavy metal transporter/detoxification protein) and CTF (cadmium tolerant factor) from Cd-exposed rice plants. RNA- and Bisulfite-sequencing revealed that both HMT/CTF genes can be induced by Cd but hypomethylated in the upstream of HMT) and downstream of CTF in Cd-exposed rice. In this project, we attempt to identify functional roles of HMT and CTF in regulating Cd uptake, translocation, accumulation and detoxification in rice. Transgenic plants overexpressing HMT/CTF will be developed and mutants of HMT/CTF will be applied to the study, which includes investigating HMT/CTF-mediated Cd uptake, translocation, and accumulation in various tissues and seeds. The transgenic rice and mutants will be validated for the physiological process. Coordinated regulation of DNA methylation/demethylation of HMT/CTF, with regard to HMT/CTF expression and Cd uptake, accumulation and detoxification will be investigated. The aim of our proposal is to uncover the roles of HMT/CTF in regulating Cd uptake, translocation and accumulation in rice, and the mechanism leading the DNA methylation involved in HMT/CTF-mediated Cd uptake and detoxification as well.