Abstract
Heavy metals are naturally occurring in the earth‘s crust but anthropogenic and industrial activities have led to drastic environmental pollutions in distinct areas. Plants are able to colonize such sites due to several mechanisms of heavy metal tolerance. Understanding of these pathways enables different fruitful approaches like phytoremediation and biofortification.Therefore, this review addresses mechanisms of heavy metal tolerance and toxicity in plants possessing a sophisticated network for maintenance of metal homeostasis. Key elements of this are chelation and sequestration which result either in removal of toxic metal from sensitive sites or conduct essential metal to their specific cellular destination. This implies shared pathways which can result in toxic symptoms especially in an excess of metal. These overlaps go on with signal transduction pathways induced by heavy metals which include common elements of other signal cascades. Nevertheless, there are specific reactions some of them will be discussed with special focus on the cellular level.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-55-35) contains supplementary material, which is available to authorized users.
Highlights
Basal heavy metal tolerance is presumably found in all plant species
Beside their activity as aggressively reacting oxidants towards cellular macromolecules they can act as signal transduction molecules which will be discussed in Section Redox signaling induced by heavy metals
General tolerance mechanisms are based on exclusion, chelation and sequestration processes (Figure 1)
Summary
Basal heavy metal tolerance is presumably found in all plant species. Thereby, they run a complex system consisting of uptake/efflux, transport/sequestration and chelation (Figure 1). This review will provide an overview about these tolerance mechanisms with focussing on the cellular level and signalling pathways induced by metals. Changes in cellular concentrations of essential micronutrients like iron, calcium, manganese, zinc
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