Characterization of a type 3 metallothionein isolated from Porteresia coarctata

Abstract

Metallothioneins are involved in detoxification of heavy metals. A cDNA encoding type 3 metallothionein (PcMT3) was isolated from the salt stressed leaf cDNA library of Porteresia coarctata (Roxb.) Tateoka (wild rice) that grows well in the heavy metal laden estuarine soils. The PcMT3 cDNA (581 bp) encodes a protein of 64 amino acids. PcMT3 is highly homologous (82 %) to OsMT-I-3a of rice, but is unique from other type 3 plant MTs due to the presence of an additional glycine residue in the C-terminal domain. Analysis of the 5′ upstream region of PcMT3 showed the presence of cis-acting elements like the CG box and STRE previously reported to be involved in gene expression under heavy metal stress. Southern analysis suggested the presence of more than one copy of PcMT3-like sequences in the P. coarctata genome. Analysis of genomic clone of PcMT3 revealed the presence of two introns. A comparison of the genomic sequence of PcMT3 with closely similar type 3 MTs from rice and mangrove species revealed conservation in the number and position of introns. Transcript profiling for PcMT3 in P. coarctata leaves in the presence of Cd, Cu and Zn showed an increase in transcript accumulation.

Diversity and distribution of plant metallothioneins: a review of structure, properties and functions

“…Other hormone-responsive elements found in pMT promoters include ERE (ethylene), MeJARE (methyl jasmonate), GARE (gibberellic acid), and SARE (salicylic acid). The discovery of these specific genetic instructions begins to answer the question why particular pMT genes are observed under certain conditions, and the identification of putative root-specific 28,66 and fruit-specific elements 67 further suggests that specific spatial expression is also programmed in these regions. It is clear that the identification and presence of elements responsive to various signals can provide important insights into the intricate interplay of pMT genes in planta, and, ultimately into their physiological function.…”

Plant Metallothioneins: Putative Functions Identified by Promoter Analysis in Silico

“…In a study of the promoter sequence of the Fagopyrum esculentum FeMT3 gene, Nikolić et al (2010) showed the presence of four MRE elements. Analyses of type 3 metallothionein gene promoters in Populus alba (MT3b) (Bereta et al, 2009), Elaeis guineensis (MT3-B) (Siti Nor Akumar et al, 2002) and Porteresia coarctata (PcMT3) (Usha et al, 2011) revealed the presence of MREs. Usha et al (2009) described the sequences of three Prosopis juliflora MTs that do not contain the MRE motif within the promoter region.…”

Analysis of tolerance to copper and zinc in Aechmea blanchetiana grown in vitro

“…However, they are also present in some sewage sludge, organic and inorganic fertilizers and fungicides and they are emitted by various human activities in amounts that could be toxic (Mantovi et al 2003, Figueiredo et al 2007. Some plant species can withstand the excess of heavy metals from the environment compartmentalizing, chelating with metallothionein or excluding them (Cheng 2003, Usha et al 2011. Cu and Zn may accumulate in plant tissues, causing many physiological and biochemical changes, growth reduction and yield loss particularly after chronic exposure (Wannaz et al 2003, Mazen 2004.…”