Plant cell responses to heavy metals ? biotechnological aspects
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Heavy metals have been increasing in the environment as a result of either natural processes or human industrial activities. Many of the heavy metals affect and damage various developmental and biochemical processes causing reduction in growth, inhibition of photosynthesis and respiration and degeneration of main cell organelles. It is mostly due to the promoting effect of heavy metals on the formation of harmful reactive oxygen species (ROS) which disturb the whole cellular machinery. There is a requirement for a balance between the uptake of essential metal ions and the ability of plants to protect sensitive cellular structures and activities from excessive level of metals. The resistance of plants to heavy metals depends on the reduction of uptake and translocation from the root to the shoot, binding by appropriate ligands and, finally, transferring to the vacuole. The phytotoxic effect of heavy metals is effectively counteracted by the metal-binding proteins and peptides like metalothioneins, chaperones and phytochelatins as well as some organic acids. Another very important aspect of the heavy metal detoxication is the presence of an efficient ROS scavenging system consisting of low molecular antioxidants and antioxidant enzymes. Some plants can hyperaccumulate metal ions that are toxic for other species. Such plants can serve as donors of traits that could be used to clean up the environment. Several methods can be applied to create plants able to remove the xenobiotics from the environment: sexual or somatic hybridization, mutagenesis, in vitro selection of metal-resistant cell lines and engineering of metal-accumulating transgenic plants. The use of specially selected and engineered metal-accumulating plants for environmental clean-up is a novel technology called phytoremediation. This rapidly emerging biotechnology consists of some branches suitable to toxic metals remediation: 1) phytoextraction ? the use of plants to remove heavy metals from the soil, 2) phytostabilization ? the use of plants to complex and eliminate the availability of toxic metals in soils, 3) rhizofiltration ? the use of plant roots to remove heavy metals from polluted waters. Some new approaches concerning the use of transgenic plants as sensitive bioindicators of toxic heavy metals and soils contaminated with radionuclides are presented.
Publication order reference
E.A. Gwozdz, Zaklad Ekofizjologii Roslin, Uniwersytet im. Adama Mickiewicza, Al. Niepodleglosci 14, 61-713 Poznan, Poland