Researchers from Aarhus University (Denmark), Polytechnic University of
Madrid (Spain), and the European Synchrotron Radiation Facility in France
have discovered that zinc plays a crucial role in the nitrogen fixation
process of legumes. The study also found that the transcriptional regulator
Fixation Under Nitrate (FUN) is a novel type of zinc sensor, which decodes
zinc signals in nodules and regulates nitrogen fixation.



Legume crops engage in symbiotic interaction with rhizobia that fixes
atmospheric nitrogen in root nodules. These nodules, however, are sensitive
to environmental factors such as temperature, drought, flooding, soil
salinity, and high soil nitrogen concentration. The researchers identified
that FUN controls nodule breakdown when soil nitrogen concentrations are
high. FUN is regulated by a peculiar mechanism that monitors the cellular
zinc levels directly. It is also inactivated by zinc into large filament
structures and liberated into the active form when zinc levels are low.



"It's truly remarkable to discover zinc's role as a secondary signal in
plants. It is a vital micronutrient, and it has never been considered as a
signal before. After screening over 150,000 plants, we finally identified
the zinc sensor FUN, shedding light on this fascinating aspect of plant
biology," Assistant Professor Jieshun Lin, the study's first author,
explains. The researchers are now investigating how zinc signals are
generated and decoded by FUN, and looking forward to applying their
discoveries to legume crops such as faba bean, soybeans, and cowpea.



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