ScMT2-1-3, a Metallothionein Gene of Sugarcane, Plays an Important Role in the Regulation of Heavy Metal Tolerance/Accumulation

Abstract

Plant metallothioneins (MTs), which are cysteine-rich, low-molecular-weight, and metal-binding proteins, play important roles in detoxification, metal ion homeostasis, and metal transport adjustment. In this study, a novel metallothionein gene, designated as ScMT2-1-3 (GenBank Accession number JQ627644), was identified from sugarcane. ScMT2-1-3 was 700 bp long, including a 240 bp open reading frame (ORF) encoding 79 amino acid residues. A His-tagged ScMT2-1-3 protein was successfully expressed in Escherichia coli system which had increased the host cell's tolerance to Cd2+, Cu2+, PEG, and NaCl. The expression of ScMT2-1-3 was upregulated under Cu2+ stress but downregulated under Cd2+ stress. Real-time qPCR demonstrated that the expression levels of ScMT2-1-3 in bud and root were over 14 times higher than those in stem and leaf, respectively. Thus, both the E. coli assay and sugarcane plantlets assay suggested that ScMT2-1-3 is significantly involved in the copper detoxification and storage in the cell, but its functional mechanism in cadmium detoxification and storage in sugarcane cells needs more testification though its expressed protein could obviously increase the host E. coli cell's tolerance to Cd2+. ScMT2-1-3 constitutes thus a new interesting candidate for elucidating the molecular mechanisms of MTs-implied plant heavy metal tolerance/accumulation and for developing sugarcane phytoremediator varieties.

Sunflower metallothionein family characterisation. Study of the Zn(II)- and Cd(II)-binding abilities of the HaMT1 and HaMT2 isoforms

“…1 and 4B) show the CC motif characteristic of this subfamily at the beginning of the N-terminal Cysrich domain, and all HaMT2 isoforms, except that of HaMT2-4, present the CCXGXCXC and CXCXXXCXGC motifs at the N-terminal domain and the GVAP tetrapeptide conserved within the spacer region [15]. Although MT2s typically exhibit eight and six Cys respectively at their N-and C-terminal domains [6], HaMT2-1 and HaMT2-4 exhibit some changes in relation to this canonical pattern.…”

“…The archetypal MT2 proteins feature eight Cys residues at their N-term Cys-rich region with a unique -Cys-Cys-motif not present in any other plant MT subfamily, and six Cys residues at their C-term domain, but again variations on the number of Cys residues exist (Table S2). Since the N-term Cys residues are highly conserved, this subfamily is further divided into several subtypes according to the arrangement of the Cys residues in the Cterminal domain [15,16]. Reported divalent metal-binding properties of recombinant plant MT2s showed their ability to bind 3.6 Zn(II) ions in the case of watermelon (Citrullus lanatus) ClMT2 [17], 3.5 Zn(II) and 5.3-6.5 Cd(II) ions for cork oak (Quercus suber) QsMT [18,19], 5 Zn(II) and 5 Cd(II) ions for chickpea (C. arietinum) cicMT2 [20], and 4.3 Zn(II) as well as 6.7 Cd(II) ions for soybean (G. max) GmMT2 [14].…”

Arbuscular mycorrhizal fungi play a role in protecting roots of Sophora viciifolia Hance. from Pb damage associated with increased phytochelatin synthase gene expression

“…Fifty micromolar Pb was a high concentration that caused damage to plant cells (Salvinia minima, A. marina, and Sophora viciifolia) after long time exposure. Guo et al (2013) reported that the expressions of SCMT2-1-3 (Saccharum spp. L.) were inhibited by Cd 2+ (500 μM) stress which were visibly down-regulated at 3 h following the treatment and maintained at a relatively lower level up to 72 h, compared to that of the control.…”

Burkholderia sp. cadmium tolerance mechanism and its influence in phytoremediation

“…Chaperones, such as and play important roles in detoxification, metal ion homeostasis, and metal transport adjustment (GUO et al, 2013), and increase plant tolerance to Cd .There are more than one type of metallothionein, Wang et al (2011) analysed two different MT, one was constitutively expressed while the other was responsive to Cd. Therefore,the presence of Cd can also not influence MT expression, this was described in tomato (present work and OUZIAD et al, 2005) and sugarcane (GUO et al, 2013), only the combination Nitrogen is an essential macronutrient, responsible for the biosynthesis of all aminoacid, protein and enzymes, despite of the decrease in nitrogen content in the presence of the bacteria, inoculated plants grew more, presenting a higher biomass, and consequently a total protein and nitrogen higher than non inoculated plants. Hu et al (2013) reported that nitrate (not ammonium) induce Cd and Zn uptake (increasing fitoextraction).…”