Zinc modulat nitrogen fixation in legumes [PB Kale, Molecular Biology and Biotechnology, Mahatma Phule Krishi Vidyapeeth Rahuri]

 "How Zinc Helps Legumes Adapt to Their Environment"

PB Kale, Molecular Biology and Biotechnology, Mahatma Phule Krishi Vidyapeeth Rahuri

Schematic diagram of the screen that resulted in the identification of FUN. Mutants producing functionally pink nodules were watered with 10 mM KNO3. Most nodules on wild-type plants became green and senescent, whereas fun mutant plants maintained pink nodules even under high concentrations of nitrate.

 - Plants adapt to changing environmental conditions by adjusting their metabolism and gene expression to maintain fitness.

- In legumes, nitrogen homeostasis is achieved by balancing nitrogen from soil and nitrogen fixation by symbiotic bacteria in root nodules.

- Zinc, an essential plant micronutrient, acts as an intracellular second messenger, linking environmental changes to metabolic activity in root nodules.

- A transcriptional regulator named FIXATION UNDER NITRATE (FUN) acts as a sensor controlled by zinc.

- Zinc controls the transition of FUN between an inactive filamentous structure and an active transcriptional regulator.

- Lower zinc concentrations in the nodule, which occur in response to higher soil nitrate levels, activate FUN by dissociating the filament.

- Activated FUN targets multiple pathways to initiate the breakdown of the nodule.

- The zinc-dependent mechanism provides a concentration readout to adapt nodule function to environmental nitrogen conditions.

- These findings highlight the role of metal ions in integrating environmental signals with plant development.

- Implications include optimizing the delivery of fixed nitrogen in legume crops.

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Reference:

Lin, J., Bjørk, P.K., Kolte, M.V. et al. Zinc mediates control of nitrogen fixation via transcription factor filamentation. *Nature* (2024). [https://doi.org/10.1038/s41586-024-07607-6]