Metallothioneins (MT) are primarily involved in metal chelation. Recent studies have shown that MT proteins are also involved in the responses of plants to various environmental stresses. The rice metallothionein-like gene OsMT-3a is upregulated by salinity and various abiotic stressors. A DNA construct containing the complete OsMT-3a coding sequence cloned downstream to the CaMV35S promoter was transformed into Arabidopsis and homozygous single-copy transgenic lines were produced. Compared to wild-type plants, transgenic plants showed substantially increased salinity tolerance (NaCl), drought tolerance (PEG), and heavy metal tolerance (CdCl2) as individual stresses, as well as different combinations of these stresses. Relevantly, under unstressed control conditions, vegetative growth of transgenic plants was also improved. The shoot Na+ concentration and hydrogen peroxide in transgenic plants were lower than those in wild-type plants. OsMT-3a-overexpressing Arabidopsis lines accumulated higher levels of Cd2+ in both shoots and roots following CdCl2 treatment. In the transgenic MT-3a lines, increased activity of two major antioxidant enzymes, catalase and ascorbate peroxidase, was observed. Thus, rice OsMT-3a is a valuable target gene for plant genetic improvement against multiple abiotic stresses.

中文翻译：

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水稻金属硫蛋白样基因OsMT-3a的组成型过表达增强了拟南芥植物的生长和对各种非生物胁迫的耐受性。

金属硫蛋白（MT）主要参与金属螯合。最近的研究表明，MT蛋白也参与了植物对各种环境胁迫的反应。盐度和各种非生物胁迫因素上调了水稻类金属硫蛋白样基因OsMT-3a。将包含克隆到CaMV35S启动子下游的完整OsMT-3a编码序列的DNA构建体转化到拟南芥中，并产生纯合的单拷贝转基因品系。与野生型植物相比，转基因植物显示出显着提高的盐分耐受性（NaCl），干旱耐受性（PEG）和重金属耐受性（CdCl2）作为单独胁迫以及这些胁迫的不同组合。相应地，在不受胁迫的控制条件下，转基因植物的营养生长也得到改善。转基因植物中的芽Na +浓度和过氧化氢低于野生型植物。在CdCl2处理后，过表达OsMT-3a的拟南芥品系在芽和根中均积累了更高水平的Cd2 +。在转基因MT-3a品系中，观察到两种主要抗氧化酶（过氧化氢酶和抗坏血酸过氧化物酶）的活性增加。因此，水稻OsMT-3a是针对多种非生物胁迫进行植物遗传改良的有价值的靶基因。