Arbuscular mycorrhiza and plant chromium tolerance

Arbuscular mycorrhizal (AM) fungi are ubiquitous soil fungi that form symbiotic associations with most terrestrial plants. The growth and functions of AM fungi depend on carbohydrates supplied by the plants, in return, the fungi assist the plants to acquire mineral nutrients (e.g., phosphorus) from soil. The AM symbiosis also improves plant survival in various unfavorable environments, such as metal (loid) contaminated soil. It has been well demonstrated that AM symbiosis improved plant adaptation to Cr contamination, which would have a great potential in phytoremediation and ecological restoration of Cr contaminated soils. In this paper, we have reviewed the role of AM fungi in alleviation of Cr phytotoxicity and associated factors influencing plant Cr tolerance. AM symbiosis improves plant Cr tolerance through its direct roles in Cr stabilization and transformation and indirect roles via AM symbiosis mediated nutrient acquisition and physiological regulation. Future research on physiological and molecular mechanisms underlying Cr behavior and detoxification in AM symbiosis, as well as potential use of AM fungi in ecological restoration and agriculture production in Cr contaminated soils were also proposed.