Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
Proc Natl Acad Sci U S A. 2010 Sep 21;107(38):16500-5. doi: 10.1073/pnas.1005396107. Epub 2010 Sep 7.
Intake of toxic cadmium (Cd) from rice caused Itai-itai disease in the past and it is still a threat for human health. Therefore, control of the accumulation of Cd from soil is an important food-safety issue, but the molecular mechanism for the control is unknown. Herein, we report a gene (OsHMA3) responsible for low Cd accumulation in rice that was isolated from a mapping population derived from a cross between a high and low Cd-accumulating cultivar. The gene encodes a transporter belonging to the P(1B)-type ATPase family, but shares low similarity with other members. Heterologous expression in yeast showed that the transporter from the low-Cd cultivar is functional, but the transporter from the high-Cd cultivar had lost its function, probably because of the single amino acid mutation. The transporter is mainly expressed in the tonoplast of root cells at a similar level in both the low and high Cd-accumulating cultivars. Overexpression of the functional gene from the low Cd-accumulating cultivar selectively decreased accumulation of Cd, but not other micronutrients in the grain. Our results indicated that OsHMA3 from the low Cd-accumulating cultivar limits translocation of Cd from the roots to the above-ground tissues by selectively sequestrating Cd into the root vacuoles.
摄入有毒的镉（Cd）曾导致过去的痛痛病，至今仍对人类健康构成威胁。因此，控制土壤中 Cd 的积累是一个重要的食品安全问题，但控制 Cd 积累的分子机制尚不清楚。在此，我们报告了一个从高 Cd 和低 Cd 积累品种杂交的作图群体中分离的、与水稻低 Cd 积累有关的基因（OsHMA3）。该基因编码一种属于 P（1B）-型 ATP 酶家族的转运蛋白，但与其他成员的相似性较低。在酵母中的异源表达表明，来自低 Cd 品种的转运蛋白具有功能，但来自高 Cd 品种的转运蛋白丧失了功能，可能是由于单个氨基酸突变。该转运蛋白主要在根细胞的液泡膜上表达，在低 Cd 和高 Cd 积累品种中的表达水平相似。低 Cd 积累品种的功能基因的过表达选择性地降低了 Cd 在谷物中的积累，但对其他微量元素没有影响。我们的结果表明，低 Cd 积累品种的 OsHMA3 通过将 Cd 选择性地螯合到根液泡中来限制 Cd 从根部向地上组织的转运。
