Guangdong Provincial Key Laboratory of Agricultural & Rural Pollution Abatement and Environmental Safety, College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510006, China.
J Hazard Mater. 2024 Dec 5;480:135827. doi: 10.1016/j.jhazmat.2024.135827. Epub 2024 Sep 12.
The Ni hyperaccumulator Odontarrhena chalcidica (formerly Alyssum murale), exhibits a significant capacity to accumulate Zn in the roots. However, the molecular mechanisms underlying the variation in Ni and Zn accumulation are poorly understood. Here, we isolated a homolog of heavy metal ATPase 3 from O. chalcidica (OcHMA3) and characterized its functions using heterologous systems. Phylogenetic analysis revealed that OcHMA3 protein shares 87.6 % identity with AtHMA3, with similar metal binding sites to other HMA3 proteins. Heterologous expression of OcHMA3 in yeast increased sensitivity to Cd, Ni and Zn, suggesting it functions as a broad-specificity transporter. Further investigation showed OcHMA3 is constitutively expressed in the roots and localized to the tonoplast. Overexpression of OcHMA3 in A. thaliana shoots increased its roots Zn concentrations by 41.9 % - 74.1 %. However, overexpression of OcHMA3 in roots enhanced its tolerance to Cd and increased roots Cd concentrations by 50.9 % - 90.6 %. Our findings indicated OcHMA3 is responsible for Zn sequestration in root vacuoles, likely leading to Zn retention in roots and subsequent Ni hyperaccumulation in shoots. This study elucidates the molecular mechanism of Ni and Zn accumulation in O. chalcidica, and identifies OcHMA3 as a potential gene for developing Zn-rich plants and for phytoextraction in Cd-contaminated soils.
镍超富集植物 Odontarrhena chalcidica（以前称为 Alyssum murale），在根部表现出很强的锌积累能力。然而，镍和锌积累差异的分子机制仍知之甚少。在这里，我们从 O. chalcidica 中分离出一种重金属 ATPase 3 的同源物（OcHMA3），并使用异源系统对其功能进行了表征。系统进化分析表明，OcHMA3 蛋白与 AtHMA3 的同源性为 87.6%，与其他 HMA3 蛋白具有相似的金属结合位点。OcHMA3 在酵母中的异源表达增加了对 Cd、Ni 和 Zn 的敏感性，表明它作为一种广谱转运蛋白发挥作用。进一步的研究表明，OcHMA3 在根部持续表达，并定位于液泡膜。在拟南芥的地上部分过表达 OcHMA3 可使其根部 Zn 浓度增加 41.9%至 74.1%。然而，在根部过表达 OcHMA3 可增强其对 Cd 的耐受性，并使根部 Cd 浓度增加 50.9%至 90.6%。我们的研究结果表明，OcHMA3 负责将 Zn 螯合到根部液泡中，这可能导致 Zn 在根部的保留以及随后在地上部分的 Ni 超积累。本研究阐明了 O. chalcidica 中 Ni 和 Zn 积累的分子机制，并确定 OcHMA3 是开发富含 Zn 的植物和用于 Cd 污染土壤的植物提取的潜在基因。
