日本冈山大学的研究人员日前在美国《国家科学院学报》上报告说,他们发现一种能抑制重金属镉在稻米中蓄积的水稻基因,该基因能把从土壤中吸收的镉封闭在水稻根部细胞内。这一发现为培育难以蓄积镉的水稻品种开辟了道路。 镉在电镀和电池生产中应用广泛,但如果镉在人体内大量蓄积,会造成骨骼中的钙大量流失,引发骨质疏松、骨骼萎缩和关节疼痛。目前,人体内积蓄的镉很难安全排出,因此防止镉从口入十分重要。 冈山大学资源生物科学研究所的科研人员分析了世界各地的约140个水稻品种,根据它们蓄积镉的难易程度将其分为两类。通过比较这些水稻的基因,研究者发现OsHMA3基因指导合成的蛋白质对于防止镉在稻米中蓄积发挥了关键作用。 在难以蓄积镉的水稻细胞内,OsHMA3基因合成的蛋白质,主要在根部细胞内负责储存代谢废物的液泡中发挥作用。这样,水稻根部吸收的镉会转移到液泡中被隔离起来。而在容易蓄积镉的品种中,OsHMA3基因及其合成的蛋白质却不具备上述功能,从而导致根部吸收的镉最终在稻米中蓄积。 研究小组认为,如果提高OsHMA3基因的性能,就有可能在镉含量很高的水田中种植水稻。如果将这种基因应用于水稻品种改良,也有望开发出难以蓄积镉的水稻新品种。 Gene limiting cadmium accumulation in rice Published online before print September 7, 2010 , doi: 10.1073/pnas.1005396107 Daisei Ueno a , Naoki Yamaji a , Izumi Kono b , Chao Feng Huang a , Tsuyu Ando b , Masahiro Yano c , and Jian Feng Ma a , 1 + Author Affiliations a Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan; b Institute of Society for Techno-innovation of Agriculture, Forestry, and Fisheries, Kamiyokoba, Tsukuba, Ibaraki, 305-0854, Japan; and c National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan Edited by Maarten J. Chrispeels, University of California at San Diego, La Jolla, CA, and approved August 19, 2010 (received for review April 20, 2010) Abstract 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.