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Chloride (Cl<sup>-</sup>) has traditionally been considered a micronutrient largely excluded by plants due to its ubiquity and abundance in nature, its antagonism with nitrate (NO<sub>3</sub><sup>-</sup>), and its toxicity when accumulated at high concentrations. In recent years, there has been a paradigm shift in this regard since Cl<sup>-</sup> has gone from being considered a harmful ion, accidentally absorbed through NO<sub>3</sub><sup>-</sup> transporters, to being considered a beneficial macronutrient whose transport is finely regulated by plants. As a beneficial macronutrient, Cl<sup>-</sup> determines increased fresh and dry biomass, greater leaf expansion, increased elongation of leaf and root cells, improved water relations, higher mesophyll diffusion to CO<sub>2</sub>, and better water- and nitrogen-use efficiency. While optimal growth of plants requires the synchronic supply of both Cl<sup>-</sup> and NO<sub>3</sub><sup>-</sup> molecules, the NO<sub>3</sub><sup>-</sup>/Cl<sup>-</sup> plant selectivity varies between species and varieties, and in the same plant it can be modified by environmental cues such as water deficit or salinity. Recently, new genes encoding transporters mediating Cl<sup>-</sup> influx (<i>ZmNPF6.4</i> and <i>ZmNPF6.6</i>), Cl<sup>-</sup> efflux (<i>AtSLAH3</i> and <i>AtSLAH1</i>), and Cl<sup>-</sup> compartmentalization (<i>AtDTX33</i>, <i>AtDTX35</i>, <i>AtALMT4,</i> and <i>GsCLC2</i>) have been identified and characterized. These transporters have proven to be highly relevant for nutrition, long-distance transport and compartmentalization of Cl<sup>-</sup>, as well as for cell turgor regulation and stress tolerance in plants.
Published in: International Journal of Molecular Sciences
Volume 20, Issue 19, pp. 4686-4686
DOI: 10.3390/ijms20194686