Arbuscular mycorrhizal fungi-based bioremediation of mercury: insights from zinc and cadmium transporter studies

Abstract

Phytoremediation, a sustainable approach for rehabilitating mercury (Hg)-contaminated soils, can be enhanced by arbuscular mycorrhizal (AM) fungi, which promote plant growth and metal uptake, including Hg, in contaminated soils. Hg, despite lacking a biological function in plants, can be absorbed and translocated using Zn and/or Cd transporters, as these elements belong to the same group in the periodic table (12/2B). In fact, the specific transporters of Hg in plant roots remain unknown. This study is therefore to provide fundamental insights into the prospect to remediate Hg-contaminated soils, with a focus on the role of AM fungi. The hypothesis posits that Hg uptake in plants may be facilitated by transporters responsible for Zn/Cd, affected by AM fungi. The Scopus database was used to collect studies between 2000 and 2022 with a focus on the ecological role of AM fungi in environments contaminated with Zn and Cd. Particular emphasis was laid on the molecular mechanisms involved in metal uptake and partitioning. The study revealed that AM fungi indeed regulated Zn and/or Cd transporters, influencing Zn and/or Cd uptake in plants. However, these effects vary significantly based on environmental factors, such as plant and AM fungi species and soil conditions (e.g., pH, phosphorus levels). Given the limited understanding of Hg remediation, insights gained from Zn and Cd transporter systems can guide future Hg research. In conclusion, this study underscores the importance of considering environmental factors and provides fundamental insights into the potential of Hg phytoremediation with the assistance of AM fungi.