The National Agriculture and Food Research Organization (NARO) has developed the "Rhizosphere Frame System" for live-imaging of the plant-microbe interactions between plant roots and symbiotic microorganisms in the soil. By this, NARO was able to continuously observe the process of establishing symbiotic relationship between rhizobia and legume roots in soil for the first time in the world. By using this system, the plant-microbe interactions will be further elucidated, and it is expected that this will lead to the development and promotion of efficient technologies for using rhizobia in agriculture, to reduce chemical fertilizer usage and greenhouse gas emissions. It is expected that this system can also be applied to other studies of plant-soil microbial interactions.
Overview
Rhizobium is one of the important soil microorganisms for agriculture. It lives in the roots of legumes such as soybean, establishes symbiotic relationships, fixes nitrogen in the atmosphere, supplies nitrogen nutrients to host plants, and plays an important role in the generation and elimination of nitrous oxide (N2O), a greenhouse gas. It is thought that understanding and utilizing the mechanism of the plant-microbe interactions between legumes and rhizobia (root nodule symbiosis) is important for the realization of sustainable agriculture, such as reducing the use of chemical fertilizers and greenhouse gases emitted from agricultural lands. However, because the roots are hidden in the soil, it is difficult to observe the plant-microbe interactions between the roots and soil microorganisms such as rhizobia. This has been an obstacle for the elucidation of the mechanism of interactions between roots and microorganisms.
Hence, NARO developed the Rhizosphere Frame System by combining a plant cultivation device "Rhizosphere Frame (RhizoFrame)" that allows the observation of roots without digging them up from the soil, with rhizobia that express fluorescent proteins. This makes it possible for the non-destructive observation of the plant-microbe interactions between plant roots and rhizobia using a fluorescence microscope. NARO was able to observe the process of establishing the symbiotic relationship between roots and rhizobia in soil using this system, for the first time in the world.
In the future, using this system, we will proceed with the research that continuously captures the symbiotic plant-microbe interactions while maintaining the positional information of soil, roots, and rhizobia. By this it is expected to deepen our understanding of root nodule symbiosis and promote the development of technologies for the efficient use of root nodule symbiosis in agriculture. This system is also expected to be applied to other studies of plant-soil microbial interactions, such as the analysis of infection processes of pathogens that infect crops.
This research results were published in the Journal of Plant Research (July 4, 2023).
Publication
Rhizosphere Frame System Enables Nondestructive Live-Imaging of Legume-Rhizobium Interactions in the Soil
Hanna Nishida, Yoshikazu Shimoda, Khin Thuzar Win, Haruko Imaizumi-Anraku Journal of Plant Research (2023) 136(5):769-780 doi: 10.1007/s10265-023-01476-2
