The Metallothionein Gene, TaMT3, from Tamarix androssowii Confers Cd2+ Tolerance in Tobacco

Abstract

Cadmium (Cd) is a nonessential microelement and low concentration Cd2+ has strong toxicity to plant growth. Plant metallothioneins, a class of low molecular, cystein(Cys)-rich and heavy-metal binding proteins, play an important role in both metal chaperoning and scavenging of reactive oxygen species (ROS) with their large number of cysteine residues and therefore, protect plants from oxidative damage. In this study, a metallothionein gene, TaMT3, isolated from Tamarix androssowii was transformed into tobacco (Nicotiana tobacum) through Agrobacterium-mediated leaf disc method, and correctly expressed under the control of 35S promoter. Under Cd2+ stress, the transgenic tobacco showed significant increases of superoxide dismutase (SOD) activity and chlorophyll concentration, but decreases of peroxidase (POD) activity and malondialdehyde (MDA) accumulation when compared to the non-transgenic tobacco. Vigorous growth of transgenic tobacco was observed at the early development stages, resulting in plant height and fresh weight were significantly larger than those of the non-transgenic tobacco under Cd2+ stress. These results demonstrated that the expression of the exogenous TaMT3 gene increased the ability of ROS cleaning-up, indicating a stronger tolerance to Cd2+ stress.

H2O2 Is Involved in the Metallothionein-Mediated Rice Tolerance to Copper and Cadmium Toxicity

“…In addition to chelating extra metal ions in plant cells via their Cys thiol groups, MTs may also enhance plant tolerance to stress by up-regulating anti-oxidative enzymes to maintain the redox balance and thereby reduce ROS-induced injury [ 15 , 17 , 37 , 38 ]. To make clear the role of ricMT on oxidative damage, rice suspension cells of sense- and antisense- ricMT transgenic lines were obtained by an Agrobacterium -mediated transformation for the first time.…”

Heavy Metal Stress and Some Mechanisms of Plant Defense Response

“…Xia et al [ 196 ] showed that expression of Elsholtzia haichowensis metallothionein type 1 ( EhMT1 ) in tobacco plants not only increased the tolerance of transgenic tobacco to copper toxicity but also decreased the synthesis of hydrogen peroxide and improved peroxidase activity (POD) in roots, leading to enhanced ability of plants to cope with oxidative stress. Zhou et al [ 9 ] demonstrated that although TaMT3 , a metallothionein type 3 from Tamarix androssowii , engineered into tobacco resulted in increased tolerance to Cd stress through significant increases of SOD functionality, which raised the ability of ROS cleaning-up in transgenic plant, it led to decreased POD activity. It seems that the impact of the expressed metallothionein on distinct components of antioxidant system of transgenic plants is different, which requires further investigation.…”

“…HMs belong to group of nonbiodegradable, persistent inorganic chemical constituents with the atomic mass over 20 and the density higher than 5 g·cm −3 that have cytotoxic, genotoxic, and mutagenic effects on humans or animals and plants through influencing and tainting food chains, soil, irrigation or potable water, aquifers, and surrounding atmosphere [ 3 – 6 ]. There are two kinds of metals found in soils, which are referred to as essential micronutrients for normal plant growth (Fe, Mn, Zn, Cu, Mg, Mo, and Ni) and nonessential elements with unknown biological and physiological function (Cd, Sb, Cr, Pb, As, Co, Ag, Se, and Hg) [ 5 , 7 – 9 ]. Both underground and aboveground surfaces of plants are able to receive HMs [ 10 ].…”

Characterization of a Type 1 Metallothionein Gene from the Stresses-Tolerant Plant Ziziphus jujuba

“…The MTs are a class of low-molecular (6–7 kDa) cysteine (Cys)-rich proteins that bind heavy metals [ 8 , 9 ], and were first reported as a cadmium binding protein in the cortex of horse kidney [ 10 ]. This protein not only has effects on detoxification of heavy metals like cadmium and mercury [ 11 ], regulation of the homeostasis of essential metals including zinc and copper [ 12 , 13 ], but also has functions like protecting reactive oxygen species [ 14 , 15 ] and DNA damage [ 16 ], in animals, plants and microorganisms. A large number of cysteine residues in MTs are able to bind a variety of metals by the formation of mercaptide bonds [ 17 ].…”