Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, People's Republic of China.
Plant Cell Rep. 2012 Jan;31(1):67-79. doi: 10.1007/s00299-011-1140-9. Epub 2011 Sep 3.
Rice (Oryza sativa L. 'Nipponbare') cDNA subtractive suppression hybridization (SSH) libraries constructed using cadmium (Cd)-treated seedling roots were screened to isolate Cd-responsive genes. A cDNA clone, encoding the rice homolog of Metal Tolerance Protein (OsMTP1), was induced by Cd treatment. Plant MTPs belong to cation diffusion facilitator (CDF) protein family, which are widespread in bacteria, fungi, plants, and animals. OsMTP1 heterologous expression in yeast mutants showed that OsMTP1 was able to complement the mutant strains' hypersensitivity to Ni, Cd, and Zn, but not other metals including Co and Mn. OsMTP1 expression increased tolerance to Zn, Cd, and Ni in wild-type yeast BY4741 during the exponential growth phase. OsMTP1 fused to green fluorescent protein was localized in onion epidermal cell plasma membranes, consistent with an OsMTP1 function in heavy metal transporting. OsMTP1 dsRNAi mediated by transgenic assay in rice seedlings resulted in heavy metal sensitivity and changed the heavy metal accumulation in different organs of mature rice under low-concentration heavy metal stress. Taken together, our results show that OsMTP1 is a bivalent cation transporter localized in the cell membrane, which is necessary for efficient translocation of Zn, Cd and other heavy metals, and maintain ion homeostasis in plant.
利用镉处理的水稻幼苗根构建的水稻 cDNA 抑制消减杂交（SSH）文库进行筛选，以分离镉应答基因。克隆到一个编码水稻金属耐受蛋白（OsMTP1）同源物的 cDNA 克隆，该基因受 Cd 处理诱导。植物 MTP 属于阳离子扩散促进剂（CDF）蛋白家族，在细菌、真菌、植物和动物中广泛存在。OsMTP1 在酵母突变体中的异源表达表明，OsMTP1 能够补偿突变株对 Ni、Cd 和 Zn 的超敏反应，但不能补偿其他金属，包括 Co 和 Mn。在对数生长期，OsMTP1 在野生型酵母 BY4741 中表达增加，提高了对 Zn、Cd 和 Ni 的耐受性。与绿色荧光蛋白融合的 OsMTP1 定位于洋葱表皮细胞质膜上，这与 OsMTP1 在重金属转运中的功能一致。通过转水稻幼苗的 RNAi 介导的 OsMTP1 实验，导致重金属敏感，并改变了成熟水稻在低浓度重金属胁迫下不同器官中的重金属积累。综上所述，我们的结果表明，OsMTP1 是一种二价阳离子转运蛋白，定位于细胞膜上，对于 Zn、Cd 和其他重金属的有效转运以及维持植物中的离子稳态是必需的。
