Cloning and characterization of a type 1 metallothionein gene from the copper-tolerant plant Elsholtzia haichowensis

Abstract

EhMT1, a type 1 metallothionein (MT) gene, was cloned from Elsholtzia haichowensis, a Cu-tolerant plant. Typical of plant type 1 MTs, EhMT1 encodes a putative peptide of 74 amino acid residues containing cysteine-rich domains. Sequence comparisons with various databases revealed strong similarities at the nucleotide and amino acid levels between EhMT1 and the type 1 MT of Mimulus guttatus. EhMT1 transcription was greater in the roots than in the leaves, and was markedly increased by treatments with Cu, H 2 O 2 , and heat shock. EhMT1-GUS was localized to the cytoplasm of onion epidermal cells. Escherichia coli cells expressing pET-30a-EhMT1 were more tolerant to Cu and accumulated more Cu than control cells. Our results show that EhMT1 is involved in Cu tolerance and accumulation in E. haichowensis.

Overexpression of Elsholtzia haichowensis metallothionein 1 (EhMT1) in tobacco plants enhances copper tolerance and accumulation in root cytoplasm and decreases hydrogen peroxide production

“…Our previous results showed that overexpression of EhMT1 increased Cu tolerance in E. coli [37]. The present study confirmed that transgenic tobacco plants expressing EhMT1 exhibit enhanced Cu tolerance and significantly improved growth of seedlings in the presence of excess Cu.…”

“…Moreover, our result for Cu distribution is also consistent with plant MTs being cytosolic proteins. Previous observations showed that EhMT1 was localized in the cytoplasm of transformed epidermal cells of onion [37]. Therefore, we suggest that Cu bound to EhMT1 most likely stays in the cytoplasm of the cell.…”

Functional characterization of a type 2 metallothionein gene, SsMT2, from alkaline-tolerant Suaeda salsa

“…An extensive number of studies has been completed in plants addressing tolerance to salinity and/or alkalinity, leading to identification of a class of plant Metallothioneins (MTs) proteins, that are associated with plant resistance extreme environmental stress 9 . MTs are a family of low molecular weight (7–10 kDa), Cys-rich proteins that bind to metals in a range of organisms, such as Oryza sativa 10 , Arabidopsis 11 , Elsholtzia haichowens is 12 , and Gossypium hirsutum 13 . MTs are divided into three classes based on the arrangement of Cys residues 14 .…”

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

“…The genes encoding the MTs have been identified and cloned from many plant species, including Arabidopsis [ 21 ], wheat [ 27 ], soybean [ 28 ], rice [ 29 ] and tomato [ 30 ], and increasing evidence suggests that plant MTs are also play an important role in physiological processes, including fruit ripening [ 31 ], root development, embryo germination [ 32 ], suberization [ 33 ] and response to multiple abiotic stresses [ 34 ]. Previous studies showed that, type 1 MT was required for Cd 2+ and Cu 2+ tolerance and accumulation [ 35 , 36 ], maintaining Zn 2+ homeostasis, confer the adaptability of plant to drought stress and scavenging reactive oxidant species (ROS) [ 14 , 37 ].…”