Overexpression of the metallothionein gene PaMT3-1 from Phytolacca americana enhances plant tolerance to cadmium
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ORIGINAL ARTICLE
Overexpression of the metallothionein gene PaMT3‑1 from Phytolacca americana enhances plant tolerance to cadmium Junkai Zhi1,2 · Xiao Liu1,2 · Peng Yin1,2 · Ruixia Yang2 · Jiafu Liu2 · Jichen Xu1,2 Received: 18 May 2020 / Accepted: 11 August 2020 © Springer Nature B.V. 2020
Abstract Metallothionein (MT) is a cysteine-rich, low-molecular-weight protein that can bind to cadmium ions and reduce their toxicity to plants. In this study, we cloned the PaMT3-1 gene encoding an unstable protein of 63 amino acids from the cadmium hyperaccumulator Phytolacca americana. The gene was inserted into a plant expression vector and introduced into tobacco plants. The cadmium content of the transgenic plants was measured after treatment with 100 mM CdCl2 for 7 days. Transgenic and wild-type roots had similar cadmium contents, whereas the cadmium content of transgenic leaves was 66.28–78.70% of the wild type. The transport coefficient of cadmium in transgenic plants was decreased by 23.31–35.52% relative to the wild type. According to various physiological indexes, including malondialdehyde content, relative electrolyte leakage, root activity, and soluble sugar content, the transgenic plants performed better than the wild type. The PaMT3-1 gene can significantly improve plant resistance to cadmium and has potential as an important gene resource in phytoremediation. Our findings could also contribute to an understanding of complex processes and mechanisms involved in phytoremediation. Key message Over-expressing a metallothionein gene PaMT3-1 from Phytolacca americana intobacco plants showed enhanced cadmium tolerance that would be important gene resource forphytoremediation. Keywords Metallothionein · Phytolacca americana L · Cadmium · Transformation · Resistance
Introduction Phytoremediation, which exploits absorption, transportation, and accumulation processes in plants, is the most effective way to treat soils contaminated with heavy metals (Stephenson et al. 2014). Numerous relevant genes, such as those encoding metallothionein (MT) (Cobbett et al. 2002), phytochelatin (PCs) (Chen et al. 2015), Natural resistance Communicated by Mohammad Faisal. Zhi Junkai and Liu Xiao contributed equally to this work * Jichen Xu [email protected] 1
Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing 100083, China
National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China
2
associated macrophage protein (NRAMP) (NakanishiMasuno et al. 2018), Yellow stripe-like protein (YSL) (Curie et al. 2009), and heavy metal ATPase (HMA) (Wang et al. 2018), have currently been identified. Metallothionein is a cysteine-rich, low-molecular-weight protein. The sulfhydryl group of cysteine can bind cadmium, zinc, and other heavy metal ions to form a barely or nontoxic complex that enhances plant tolerance to metal toxicity and facilitates their accumulation. Several gene transformation experiments have definitively confirmed that meta
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