Analysis of ferrous ion acquisition pathways in relation to cadmium tolerance and accumulation abilities of higher plants.

主要二价金属的耐受性和积累能力。对日本200多个草本被子植物种（亚种）的e、Fe、Cu、Zn和Cd含量进行了比较。然后，从具有较高/较低镉耐受性和积累能力的典型植物中分离出铁转运蛋白（IRTs）等在二价金属从土壤向根系转运中起主要作用的基因，并对其序列进行比较。结果表明，分子某一特定单元的氨基酸序列与母系植物的耐镉和镉积累能力存在一定程度的相关性。另外，通过对多个水稻品种的生理试验和统计分析表明，根、茎部二价金属的转运对镉积累能力的分化起着重要的作用。此外，利用烟草进行的分子/生理实验表明，调控缺铁响应基因（如NtIRT1和NtFRO2）表达的信号是一种远程和局部混合传播的信号，该信号正向调节基因表达，每个组织都可以产生该信号，并根据其缺铁水平定量影响其强度。本研究清除的植物中与金属稳态相关的知识将是开发植物修复和/或无公害种植的特殊植物的关键。

Tolerance and accumulation abilities for major divalent metals(i.e, Fe, Cu, Zn and Cd) were compared among more than 200 species/subspecies of herbal angiosperms in Japan. Then, some genes, which play a major role to transport divalent metals from the soil to roots, such as iron transporters (IRTs), were isolated from typical plants showing higher/lower cadmium tolerance and accumulation abilities, and the sequences were compared from each others. Results demonstrated that a level of correlation could be seen between the amino acid sequences at a specific unit of the molecule and the cadmium tolerance and accumulation abilities of the mother plant species. Also, physiological experiments using many rice cultivars and the statistical analyses of the results showed that root shoot divalent metal transports could play a very important role to differentiate the accumulation ability of cadmium. Furthermore, molecular/physiological experiments using tobacco indicated that, the signal regulating expression of iron-deficiency responsive genes (e.g. NtIRT1 and NtFRO2) was a mixture of long-distance- and local transmission, the signal positively regulated the gene expressions, every tissue could generate the signal and quantitatively affect the strength dependent on their level of iron deficiency. The knowledge related to metal homeostasis in plants cleared by this study would be a key to develop special plants for phytoremediation and/or contaminant-free cropping.