Metallothioneins are cysteine-rich proteins, which play key roles in metal detoxification, intracellular ion homeostasis maintenance, and protection against intracellular oxidative damage. This study reports the characterization of SbMT-2 cloned from Salicornia brachiata concerning physiology, molecular, and photosynthesis efficiency. Overexpression of SbMT-2 conferred enhanced tolerance to Zn stress in transgenic tobacco supported by increased photosynthesis efficiency and crop quality compared to wild-type. The growth of transgenic and WT plants was comparable in control conditions; transgenic plants showed better growth than WT plants under stress (20 mM ZnSO₄ for 30 days). After 30 days of stress, transgenic plants completed their life cycle with early maturation, whereas the WT plants did not and matured very late. About 35 pods with a total weight of 3.5 g per plant were measured in transgenic compared to WT (about 19 pods with total weight 2.5 g). Further, gas exchange and fluorescence measurements established that the SbMT-2 gene improved the photosynthetic efficiency of the transgenic line compared to WT plants during stress conditions. In addition, SbMT-2 might be involved in the selective translocation of Zn²⁺ under long-term stress condition. Microarray analysis showed that the expression of many Zn transporters, Zn-binding proteins, and Zn-associated proteins encoding genes was up-regulated 4–6 (log2) fold. However the expression of genes encoding other metal-binding proteins, metal metabolism-associated enzymes, and metal-inducible transcription factors were down-regulated. Furthermore, transcript expression analysis elucidated that overexpression of the SbMT-2 gene may regulate the expression pattern of metal transporter encoding genes under stress conditions. Thus, SbMT-2 is an important gene, which plays a positive role by detoxifying reactive oxygen species and maintaining photosynthesis efficiency under Zn stress conditions.

金属硫蛋白是富含半胱氨酸的蛋白质，在金属解毒、细胞内离子稳态维持和防止细胞内氧化损伤中起关键作用。本研究报告了从Salicornia brachiata克隆的SbMT-2在生理、分子和光合作用效率方面的表征。与野生型相比，SbMT-2 的过表达增强了转基因烟草对锌胁迫的耐受性，这支持了光合作用效率和作物质量的提高。转基因和野生型植物的生长在对照条件下相当；转基因植物在胁迫（20 mM ZnSO ₄30 天）。经过 30 天的胁迫后，转基因植物在早期成熟的情况下完成了它们的生命周期，而 WT 植物则没有并且成熟得很晚。与 WT（约 19 个豆荚，总重量为 2.5 g）相比，在转基因中测量了大约 35 个豆荚，每株植物的总重量为 3.5 g。此外，气体交换和荧光测量确定SbMT-2基因在胁迫条件下与 WT 植物相比提高了转基因品系的光合效率。此外，SbMT-2可能参与 Zn ²⁺的选择性易位在长期的压力条件下。微阵列分析显示，许多锌转运蛋白、锌结合蛋白和锌相关蛋白编码基因的表达上调 4-6 (log2) 倍。然而，编码其他金属结合蛋白、金属代谢相关酶和金属诱导转录因子的基因的表达被下调。此外，转录表达分析阐明了SbMT-2基因的过度表达可能会在压力条件下调节金属转运蛋白编码基因的表达模式。因此，SbMT-2是一个重要的基因，它在锌胁迫条件下通过解毒活性氧和维持光合作用效率发挥积极作用。