How metal-tolerant ecotypes of ectomycorrhizal fungi protect plants from heavy metal pollution.

Abstract

Introduction: Heavy metal pollution is a strong driver of above- and belowground communities and triggers evolutionary adaptation in organisms. This review provides an overview of our knowledge on the effects of toxic concentrations of metals on ectomycorrhizal populations and communities. Discussion: Selection and adaptations within particular ectomycorrhizal species that colonise host plants in harsh environments is discussed. Among these adaptations, we focus on the metal exclusion strategy that is discovered in metal-tolerant ecotypes of Suillus species that thrive on metalliferous soils. Metal efflux in metal-tolerant ecotypes prevents metal overloading of cytoplasm and vacuole. At the same time, this metal-specific efflux system in Suillus seems to reduce the transfer of large quantities of metals towards the plant-fungus interface, without hampering normal nutrient transfer to the host plant. Conclusion: The evolutionary adaptation in Suillus species contributes to the survival of host trees on metalliferous soils and might be exploited in phytostabilisation strategies for heavy-metal contaminated soils.