锰（Mn）是植物生长发育不可或缺的微量元素之一，也是人与动物机体所必需。植物吸收与运输Mn的分子机制已被相继解析，但籽粒Mn累积过程还不清楚。我们通过前期玉米籽粒矿质元素含量的关联分析发现，ZmNRAMP7和ZmMTP11两种不同类型的金属转运蛋白基因参与了籽粒Mn的累积。生化分析表明其编码蛋白都定位在反式高尔基体网络（TGN），分别介导TGN-Mn的外运和内运过程，从而协同调控细胞内Mn的分配。本课题拟围绕TGN-Mn转运如何影响籽粒Mn累积这一关键科学问题，系统开展ZmNRAMP7和ZmMTP11的基因功能研究、表达部位与模式分析，从生理、遗传和分子层面深入解析它们协同互作调控籽粒Mn累积的关键机制。同时利用候选基因关联分析挖掘目标基因的优良等位变异并功能验证。研究结果将阐明TGN上的Mn内/外运蛋白协同调控籽粒Mn累积的新颖机制，并提供优异基因/等位变异资源用于作物营养强化育种。

Manganese (Mn) is an essential trace element for growth of plants, as well as animal and humans. Uptake and translocation of Mn have been well described in planta, but the grain-loading of Mn remains largely unknown. Our previous study on genome-wide association analysis of maize grain mineral concentrations indicated that two types of metal transporter, ZmNRAMP7 and ZmMTP11, were involved in the accumulation of Mn in grain. Interestingly, ZmNRAMP7 and ZmMTP11 encoded proteins localized to trans-Golgi network (TGN) but mediated Mn import and export, respectively, which may regulate the intracellular distribution of Mn in plant cells. To address the key question how the intracellular distribution of Mn by these two TGN transporters regulates the Mn accumulation in grain, this project aims to investigate the genes function and regulation using different approaches, including gene expression analysis, tissue location analysis, and grain Mn accumulation and distribution phenotypes in maize Crispr/cas9 mutants and over-expression transgenic lines. In addition, candidate-gene based association analysis will be performed to identify the functional alleles’ variation of two target genes with in a maize association panel. With these findings, we expect to understand the novel mechanism of regulating grain Mn by TGN-localized Mn transporters, and provide the valuable gene and natural variation for breeding biofortification crops.