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Researchers in France have discovered that zinc plays a crucial role in the health of legume crops. This is a breakthrough as it
could significantly enhance crop yields and improve the resilience of crops to climate change.
The study by researchers at Denmark’s Aarhus University, in collaboration with the Polytechnic University of Madrid, was published in the Nature journal.
It found that zinc in plants aids in nitrogen fixation, a process where atmospheric nitrogen is converted into ammonia, an essential nutrient for plants.
Legume crops form a symbiotic relationship with rhizobia, a bacteria that fixes atmospheric nitrogen in root nodules.
However, these nodules are sensitive to environmental factors such as temperature, drought, flooding, soil salinity, and high soil nitrogen levels.
Another vital finding of this study is the identification of a crucial transcription factor that controls nodule breakdown when soil nitrogen levels are high.
The researchers discovered that legumes also use zinc as a secondary signal to integrate environmental factors and regulate nitrogen fixation efficiency. The mechanism works due to a transcriptional regulator called Fixation Under Nitrate (FUN).
“It’s truly remarkable to discover zinc’s role as a secondary signal in plants. As a vital micronutrient, its signalling function was previously unknown. After screening over 150,000 plants, we identified the zinc sensor FUN, revealing this fascinating aspect of plant biology,” Jieshun Lin, study’s first author was quoted.
“FUN is regulated by a unique mechanism that monitors cellular zinc levels,” explained Kasper Røjkjær Andersen.
FUN is inactivated by zinc through the formation of large filament structures, which are dismantled to release active FUN when zinc levels are low.
The continued fixation of nitrogen could be seen as a beneficial trait that increases nitrogen availability, both for the legume and for crops that rely on the nitrogen left in the soil after legumes are grown.
Way forward
By understanding how nitrogen fixation is regulated by zinc and FUN, strategies are being developed by researchers to optimise this process in legume crops. This could result in increased nitrogen delivery, improved crop yields, and a reduced need for synthetic fertilisers, which carry environmental and economic costs.
The mechanisms by which zinc signals are generated and decoded by FUN are now being investigated by researchers. These new discoveries can be applied to legume crops such as fava beans, soybeans, and cowpeas.