Regulation of chloride transport by regulatory components of nitrate homeostasis

Chloride (Cl−is an essential micronutrient that has traditionally been considered harmful to agriculture. Both Cl− and nitrate (NO3−), an essential nitrogen source, are the most abundant inorganic anions in plants. While it is currently believed that plants prioritize the uptake of NO3 over that of Cl−, it is now evident that plants use a large amount of metabolic energy to accumulate Cl− at macronutrient levels, allowing more efficient uses of nitrogen, carbon and water in plants (Colmenero Flores et al, 2019; Cakmak et al, 2023). Presently, plasma membrane proteins involved in root Cl- uptake are still unknown in Arabidopsis thaliana. Only the NO3 − transceptor (transporter + receptor) AtNPF6.3 has been shown to mediate Cl− uptake when NO3- is very scarce or absent from the rhizosphere (Wen et al, 2018; Xiao et al, 2021). We hypothesize that reciprocal regulation of NO3 vs Cl− homeostasis in plants is more complex than currently believed. We aim to study how the availability of NO3 affects Cl− uptake, and whether the transporters and regulatory components involved in nitrate NO3- transport are also involved in Cl−uptake. In addition, we want to accurately quantify what percentage of the Cl− taken up by the plant depends on AtNPF6.3. Chloride uptake has been quantified in mutant lines of Arabidopsis thaliana with lack of function for different transporters and regulatory components of NO3− uptake mechanisms. Applying different concentrations of NO3 in the irrigation solutions, and Cl− at levels required to fulfil micro‐ or macro nutrient requirements. Our results showed that high‐affinity NO3- transporters did not participate in Cl− transport, while the double‐affinity AtNPF6.3 transporter mediated Cl− transport only under conditions of low NO3- availability. In addition, mutant lines with reduced NO3- content showed an increase in Cl− accumulation. We propose that this responds to a compensatory mechanism that allows a more efficient use of NO3- when this relevant nitrogen source limits plant growth. On the other hand, our results point to the occurrence of an intracellular NO3− sensor that negatively regulates Cl− uptake when there is an adequate availability of NO3− in the rhizosphere. Finally, it should be noted that Cl− uptake mediated by AtNPF6.3 only represents 20% of the total Cl− accumulated in A. thalina, indicating that the most important Cl- uptake mechanisms are yet to be identified in plants References Colmenero‐Flores et al, 2019 Cakmak et al, 2023 Wen et al, 2018 Xiao et al, 2021

Bibliographic Details

Main Authors:	Romero-Jiménez, David, Peinado-Torrubia, Procopio, Durán Gutiérrez, Francisco J., Rosales Villegas, Miguel Á., Colmenero Flores, José M.
Other Authors:	Ministerio de Ciencia e Innovación (España)
Format:	comunicación de congreso biblioteca
Language:	English
Published:	Sociedade Portuguesa de Biologia de Plantas 2023
Online Access:	http://hdl.handle.net/10261/357760
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