Effects of Phytochelatin-like Gene on the Resistance and Enrichment of Cd 2+ in Tobacco.

Phytochelatins (PCs) are class III metallothioneins in plants. They are low molecular-weight polypeptides rich in cysteine residues which can bind to metal ions and affect the physiological metabolism in plants. Unlike other types of metallothioneins, PCs are not the product of gene coding but are synthesized by phytochelatin synthase ( PCS ) based on glutathione (GSH). The chemical formula of phytochelatin is a mixture of (γ-Glu-Cys) _n -Gly (n = 2-11) and is influenced by many factors during synthesis. Phytochelatin-like ( PCL ) is a gene-encoded peptide (Met-(α-Glu-Cys) ₁₁ -Gly) designed by our laboratory whose amino acid sequence mimics that of a natural phytochelatin. This study investigated how PCL expression in transgenic plants affects resistance to Cd and Cd accumulation. Under Cd ²⁺ stress, transgenic plants were proven to perform significantly better than the wild-type (WT), regarding morphological traits and antioxidant abilities, but accumulated Cd to higher levels, notably in the roots. Fluorescence microscopy showed that PCL localized in the cytoplasm and nucleus.