Authors
Murray, J. D., Xiao, Q., Wang, J., Chen, Y., Li, F., Jiwu, W., Miller, A. J.
Abstract
Nitrate uptake in plants is mediated by Nitrate Transporter 2 (NRT2) and NRT1.1 proteins via proton symport. The apoplast of root epidermal cells serves as an intermediate compartment for plant nutrient uptake from the rhizosphere. We tested the effects of nitrate uptake on external media pH (pHmed) and apoplastic pH (pHapo) in nrt1.1 and nrt2.1 mutants of M. truncatula. Monitoring of pHmed showed that loss of NRT2.1 largely prevented nitrate induced alkalization of the media, while loss of NRT1.1A/B reduced media alkalization only during the initial stages of nitrate uptake. Use of the pH sensitive dye HPTS showed that pHapo of root cells decreased during nitrate uptake, and this affect was partly attenuated in the nitrate transporter mutants. To explain the discrepancies between the observed changes in pHmed and pHapo during nitrate uptake, we propose the following model. We suggest that the depletion of protons in the media that occurs during nitrate symport is offset by the buffering of protons in the cell wall and the activity of the H+-ATPase, allowing a lower pHapo to be maintained. Such a mechanism would enable efficient nitrate uptake across a range of external pH values.
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bioRxiv
The authors list and abstract were imported from bioRxiv on 04 Nov 2025.
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