Mechanisms Underlying Heavy Metal Tolerance in Arbuscular Mycorrhizas
Arbuscular mycorrhizal fungi are able to tolerate a wide range of metal concentrations in soils. A number of passive and active molecular processes are employed by these fungi to maintain metal homeostasis. The main passive mechanism is the binding of metals to the fungal walls, responsible for a significant percentage of the metal retained. Meanwhile in the cytosol, a number of chelators (metallothioneins, glutathione) bind the metals very efficiently. Heavy metal transporters collaborate with the intracellular chelators to actively reduce the levels of metal by pumping metal out of the cytosol. Additionally, the fungus strives to reduce the free radicals produced by heavy metals. In this chapter, we discuss the most recent progress in the identification and characterization of the elements involved in maintaining metal homeostasis in arbuscular mycorrhizal fungi, as well as how the heavy metal control systems of the plant are affected by the development of the symbiosis.
KeywordsArbuscular Mycorrhizal Fungus Mycorrhizal Fungus Arbuscular Mycorrhiza Ectomycorrhizal Fungus Mycorrhizal Plant
The authors are grateful to the Consejería de Innovación, Ciencia y Empresa of the Andalusian Autonomic Governement (ref. P06-CVI-02263) for financial support to part of the work reported here. Karim Benabdellah was supported by an I3P contract from the Spanish Council for Scientific Research (CSIC).
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