The isolation and characterization of Type 1 metallothionein (MT) cDNA from a heavy-metal-tolerant plant, Festuca rubra cv. Merlin

Festuca rubra cv. Merlin originated from lead and zinc mining areas in the UK has shown multi-metal tolerance ability in laboratory studies. A Type I metallothionein (MT) gene mcMT1 was cloned from the copper induced cDNA library of F rubra cv. Merlin. The mcMT1 cDNA was 492 bp in full length, including a 50 bp 5' noncoding domain, 213 bp open reading frame and a 211 bp 3' termination. The coding region of mcMT1 represented a putative 70-amino acid protein with a molecular weight of 7.1 kDa. At each of the N- and G terminal of the putative protein, six cysteine residues were arranged in a CXCXXXCXCXXXCXC and CXCXXXCXCXXCXC structure, respectively, indicating that it was a Type I MT. Southern blot hybridization suggested that there were at least two loci for the mcMT1 gene in the genome. Northern blot analysis showed an enhanced and persistent expression of mcMT1 in the F. rubra, Merlin within 24 h upon copper and cadmium exposure. Functional complementation studies using the Saccharomyces cerevisiae cup1(Delta) mutant ABDE-1 (metal sensitive) confirmed the functional nature of this mcMT1 gene in sequestering both essential (Cu, Zn) and non-essential metals (Cd, Pb, Cr). (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.