Metal nutrition and transport in the process of symbiotic nitrogen fixation

The symbiotic nitrogen fixation (SNF) facilitated by the interaction between legumes and rhizobia is a well-documented and eco-friendly alternative to chemical nitrogen fertilizers. Host plants obtain fixed nitrogen from rhizobia by providing carbon and mineral nutrients. These mineral nutrients, which are mostly in the form of metal ions, are implicated in various stages of SNF process. This review elucidates the functional roles that metal ions play in nodule formation and nitrogen fixation, and specifically addresses the transport mechanisms of metal ions and the associated transporters within root nodules. Future research directions and potential strategies to enhance the SNF efficiency are also discussed.