Cellular basis of the legume-rhizobium symbiosis.

Abstract

The legume-rhizobium symbiosis represents the most important system for terrestrial biological nitrogen fixation. During the legume-rhizobium symbiosis, efficient nitrogen fixation depends on successful rhizobia infection and complete endosymbiosis, which are achieved by complicated cellular events involving cell wall remodeling, cytoskeletal reorganizations, and extensive membrane expansion and trafficking. In this review, we depict dynamic remodeling of the plant-unique cell Wall-Membrane system-Cytoskeleton continuum during symbiotic nitrogen fixation, especially in rhizobia uptake, infection thread formation and elongation, rhizobia droplet release, cytoplasmic bridge formation, and rhizobia endosymbiosis for efficient nitrogen fixation. We finally discuss the advanced techniques for deeply exploring the cellular basis of root nodule symbiosis, and provide insights into the unsolved mysteries of robust symbiotic nitrogen fixation.