Guangdong Provincial Key Laboratory of Plant Resource, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China.
Planta. 2012 Mar;235(3):523-37. doi: 10.1007/s00425-011-1527-4. Epub 2011 Oct 5.
Metallothioneins (MTs) are small, cysteine-rich and metal-binding proteins which are involved in metal homeostasis and scavenging of reactive oxygen species. Although plant MTs have been intensively studied, their roles in seeds remain to be clearly established. Here, we report the isolation and characterization of NnMT2a, NnMT2b and NnMT3 from sacred lotus (Nelumbo nucifera Gaertn.) and their roles in seed germination vigor. The transcripts of NnMT2a, NnMT2b and NnMT3 were highly expressed in developing and germinating sacred lotus seeds, and were dramatically up-regulated in response to high salinity, oxidative stresses and heavy metals. Analysis of transformed Arabidopsis protoplasts showed that NnMT2a-YFP and NnMT3-YFP were localized in cytoplasm and nucleoplasm. Transgenic Arabidopsis seeds overexpressing NnMT2a and NnMT3 displayed improved resistance to accelerated aging (AA) treatment, indicating their significant roles in seed germination vigor. These transgenic seeds also exhibited higher superoxide dismutase activity compared to wild-type seeds after AA treatment. In addition, we showed that NnMT2a and NnMT3 conferred improved germination ability to NaCl and methyl viologen on transgenic Arabidopsis seeds. Taken together, these data demonstrate that overexpression of NnMT2a and NnMT3 in Arabidopsis significantly enhances seed germination vigor after AA treatment and under abiotic stresses.
金属硫蛋白（MTs）是一种富含半胱氨酸和金属结合的蛋白质，参与金属稳态和活性氧的清除。虽然植物 MTs 已经得到了深入的研究，但它们在种子中的作用仍有待明确。在这里，我们从荷花（Nelumbo nucifera Gaertn.）中分离并鉴定了 NnMT2a、NnMT2b 和 NnMT3，并研究了它们在种子活力方面的作用。NnMT2a、NnMT2b 和 NnMT3 的转录本在发育和萌发的荷花种子中高度表达，并对高盐、氧化应激和重金属有显著的上调反应。对转化的拟南芥原生质体的分析表明，NnMT2a-YFP 和 NnMT3-YFP 定位于细胞质和核质中。过表达 NnMT2a 和 NnMT3 的转基因拟南芥种子对加速老化（AA）处理表现出更好的抗性，表明它们在种子活力方面的重要作用。这些转基因种子在 AA 处理后也表现出比野生型种子更高的超氧化物歧化酶活性。此外，我们表明，NnMT2a 和 NnMT3 赋予了转基因拟南芥种子在 NaCl 和甲基紫精处理下更好的发芽能力。综上所述，这些数据表明，在拟南芥中过表达 NnMT2a 和 NnMT3 可以显著增强 AA 处理后和非生物胁迫下的种子活力。
