An Insight into Phytoremediation of Heavy Metals from Soil Assisted by Ancient Fungi from Glomeromycota-Arbuscular Mycorrhizal Fungi

Abstract

Arbuscular Mycorrhizal (AM) fungi form mutualistic relationship with plant roots which improves plant growth and confers tolerance against many types of stresses, including heavy metals tolerance. AM fungi allows enhanced-growth of plants, grown on heavy metals contaminated soil. They have been involved in regulating the uptake of heavy metals from root to shoot exploiting the potential of membrane transporters. These fungi either increase the uptake of heavy metals from root to shoot (phytoextraction) or stop their spreading in soil, using different mechanisms including accumulation of toxic metals in hyphae, chelation of metals with substances released by fungal hyphae or adhering these metals with roots surface or chitin of fungal cell wall. The latter approach, used by AM fungi, is known as phytostabilization, which stops the dissemination and leakage of heavy metals in the soil keeping the ecosystem in equilibrium and makes it suitable for optimum plant growth. Apart from this, spores isolated from the heavy metals contaminated soil have shown enhanced resistance to presence of heavy metals than non-contaminated soil. Such acquired resistance or tolerance is not durable as it has not being developed as a result of genetic changes but due to phenotypic plasticity of spores. Such resistance may be lost if these spores are being grown on non-heavy-metals-contaminated soil. For efficient phytoremediation, the potential of plant transporters in response to AM fungi should be exploited. It would be ideal to see if these membrane transporters genes could be expressed by AM fungal promoters for enhanced metals remediation and restoring the damaged ecosystem.