Phytochelatins and Their Roles in Heavy Metal Detoxification
Year: 2000
Type: review
Abstract: Plants respond to heavy metal toxicity in a variety of different ways. Such responses include immobilization, exclusion, chelation and compartmentalization of the metal ions, and the expression of more general stress response mechanisms such as ethylene and stress proteins. These mechanisms have been reviewed comprehensively by Sanita di Toppi and Gabbrielli (1999)for plants exposed to Cd, the heavy metal for which there have been arguably the greatest number and most wide-ranging studies over many decades. Understanding the molecular and genetic basis for these mechanisms will be an important aspect of developing plants as agents for the phytoremediation of contaminated sites (Salt et al., 1998). One recurrent general mechanism for heavy metal detoxification in plants and other organisms is the chelation of the metal by a ligand and, in some cases, the subsequent compartmentalization of the ligand-metal complex. A number of metal-binding ligands have now been recognized in plants. The roles of several ligands have been reviewed by Rauser (1999). Extracellular chelation by organic acids, such as citrate and malate, is important in mechanisms of aluminum tolerance. For example, malate efflux from root apices is stimulated by exposure to aluminum and is correlated with aluminum tolerance in wheat (Delhaize and Ryan, 1995). Some aluminum-resistant mutants of Arabidopsis also have increased organic acid efflux from roots (Larsen et al., 1998). Organic acids and some amino acids, particularly His, also have roles in the chelation of metal ions both within cells and in xylem sap (Kramer et al., 1996;Rauser, 1999).
Source: PLANT PHYSIOLOGY
DOI: 10.1104/pp.123.3.825
Author: Christopher S. Cobbett
Institution: The University of Melbourne
Language: English
Topic: Heavy metals in environment
Subfield: Pollution
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2118150573