A new study reveals the critical role of zinc in regulating nitrogen fixation in legumes through a sensor called FUN. This discovery could help improve crop efficiency and reduce the use of synthetic fertilizers by adapting to environmental and soil conditions.
Researchers have discovered that zinc significantly affects the process of nitrogen fixation in legumes, a discovery that could transform legume-based agriculture.
Climate change, drought, increased temperature and other stressors challenge agricultural sustainability. Researchers have now made an unexpected discovery: zinc plays a key role in plants’ response to abiotic stress. This groundbreaking discovery not only sheds light on the complex mechanisms of plant growth, but also promises to revolutionize crop resilience, especially in legume-based agriculture.
Lotus japonicus. Credit: Helene Eriksen
Discovering the role of zinc in nitrogen fixation
Scientists have discovered a vital role of zinc in the nitrogen fixation process of legumes. This discovery, coupled with insights into the transcriptional regulator known as Fixation Under Nitrate (FUN), has the potential to transform legume agriculture by increasing crop efficiency and reducing reliance on synthetic fertilizers. By delving into the mechanisms through which zinc and FUN control nitrogen fixation, researchers aim to increase nitrogen availability, improve crop yields and promote more environmentally friendly agricultural methods.
Legumes form a symbiotic relationship with rhizobia bacteria, which fix atmospheric nitrogen in the root nodules. However, these nodes are sensitive to various environmental stresses such as changes in temperature, drought, flooding, soil salinity and high levels of soil nitrogen.
Advances in Plant Micronutrient Sensing
Researchers from Aarhus University, in collaboration with the Polytechnic University of Madrid and the European Synchrotron Radiation Agency in France, have discovered that legumes use zinc as a secondary signal to integrate environmental factors and regulate the efficiency of nitrogen fixation. In the study published in Natureresearchers discovered that FUN is a new type of zinc sensor, which decodes zinc signals in nodules and regulates nitrogen fixation.
“It is truly remarkable to discover the role of zinc as a secondary signal in plants. It is a vital micronutrient and has never before been considered a signal. After screening over 150,000 plants, we finally identified the FUN zinc sensor, shedding light on this fascinating aspect of plant biology,” explains assistant professor Jieshun Lin, first author of the study.
Jieshun Lin showing root nodes on a Lotus japonicus. Credit: Helene Eriksen
Discovery of FUN protein functionality
In this study the researcher identifies that FUN is an important transcription factor that controls nodulation when soil nitrogen concentrations are high: “FUN is regulated by a distinct mechanism that directly monitors cellular zinc levels, and we show that FUN is inactivated by zinc in large filament structures and are released in the active form when zinc levels are low,” explains Professor Kasper Røjkjær Andersen.
From an agricultural perspective, continuous nitrogen fixation can be a beneficial trait that increases nitrogen availability, both for legumes and for co-cultured or future crops that rely on nitrogen remaining in the soil after legume growth. This helps to lay the foundation for future research that provides us with new ways to manage our agricultural systems and reduce the use of nitrogen fertilizers and reduce its impact on the environment.
Increasing agricultural efficiency and sustainability
The implications of this research are significant. By understanding how zinc and FUN regulate nitrogen fixation, researchers are developing strategies to optimize this process in legume crops. This can lead to increased nitrogen availability, improved plant yields and reduced need for synthetic fertilizers, which have environmental and economic costs.
Researchers are now investigating the mechanisms of how zinc signals are generated and decoded by FUN. They look forward to applying these new discoveries to legume crops such as beans, soybeans and green peas.
The research team gathered at the laboratory premises at Aarhus University. Credit: Helene Eriksen
Reference: “Zinc mediates control of nitrogen fixation via transcription factor filamentation” by Jieshun Lin, Peter K. Bjørk, Marie V. Kolte, Emil Poulsen, Emil Dedic, Taner Drace, Stig U. Andersen, Marcin Nadzieja, Huijun Liu , Hiram Castillo-Michel, Viviana Escudero, Manuel González-Guerrero, Thomas Boesen, Jan Skov Pedersen, Jens Stougaard, Kasper R. Andersen, and Dugald Reid, 26 June 2024, Nature.
DOI: 10.1038/s41586-024-07607-6
This work was supported by the Enabling Nutrient Symbioses in Agriculture (ENSA) project, funded by Bill & Melinda Gates Agricultural Innovations (INV- 57461), the Bill & Melinda Gates Foundation and the Foreign, Commonwealth and Development Office (INV-55767). ), the Carlsberg Foundation grant (CF21-0139) and the European Research Council (ERC) under the European Union research and innovation program Horizon 2020 (grant agreement no. 834221).
Jieshun Lin, Peter K. Bjørk, Jens Stougaard, Kasper R. Andersen and Dugald Reid are inventors on a filed patent that captures these discoveries.