Analysis of BnMTL, a novel metallothionein-like protein in the bast fiber crop Ramie (Boehmeria nivea).

Ramie (Boehmeria nivea) is a perennial herb that is highly tolerant of heavy metals. In the present study, we cloned a novel metallothionein-like gene from ramie; this gene, termed BnMTL, encodes a putative 46 amino acid protein with a molecular mass of 4.38 kDa. Analysis using quantitative RT-PCR revealed that cadmium (Cd ²⁺ ) treatment results in elevated expression of BnMTL in the roots. We heterologously overexpressed BnMTL in Escherichia coli cells to examine its binding to Cd ²⁺ and its possible role in homeostasis. Recombinant E. coli cells expressing BnMTL exhibited a high tolerance of Cd ²⁺ stress up to a concentration of 1 mm, and the observed accumulation of Cd ²⁺ was almost eight-fold higher than the control. These results demonstrate that BnMTL (i) is highly expressed in the root following exposure to Cd ²⁺ and (ii) encodes a typical metallothionein-like protein with high cadmium-binding activity.
(© 2019 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.)