Chloride as multifunctional beneficial ion: biological functions and regulation

Chloride (Cl-) has been generally considered a toxic anion rather than a plant nutrient. However we have recently shown that, in addition to an essential micronutrient, Cl- is a beneficial macronutrient (Franco-Navarro et al, 2016). Under non-saline conditions (1-5 mM), Cl- specifically stimulates higher leaf cell size and leads to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. Chloride plays specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl- regulates water relations at the whole plant level through reduction of plant transpiration. This is a consequence of a lower stomatal conductance, which results in lower water loss and greater photosynthetic and integrated water-use efficiency (Franco-Navarro et al, 2016). We are currently studying the interaction of Cl- homeostasis with: i) plant development; ii) water deficit tolerance; iii) carbon and nitrate (NO3-) assimilation. These points will be addressed at the physiological level, and data concerning the molecular regulation of Cl- nutrition and Cl-/NO3- interaction (Cubero-Font et al., 2016) will be presented. - Franco-Navarro et al. (2016) Chloride regulates leaf cell size and water relations in tobacco plants. Journal of Experimental Botany 67 (3): 873-891. - Cubero-Font et al. (2016) Silent S-Type Anion Channel Subunit SLAH1 Gates SLAH3 Open for Chloride Root-to-Shoot Translocation. Current Biology 26 (16): 2213-2220.MINECO-FEDER grants AGL2009-08339/AGR and AGL2015-71386-R.Peer Reviewe