The Arabidopsis vacuolar anion transporter, AtCLCc, is involved in the regulation of stomatal movements and contributes to salt tolerance

Abstract

SUMMARYIn plant cells, anion channels and transporters are essential for key functions such as nutrition, resistance to biotic or abiotic stresses, and ion homeostasis. In Arabidopsis, members of the chloride channel (CLC) family located in intracellular organelles have been shown to be required for nitrate homeostasis or pH adjustment, and previous results indicated that AtCLCc is involved in nitrate accumulation. We investigated new physiological functions of this CLC member in Arabidopsis. Here we report that AtCLCc is strongly expressed in guard cells and pollen and more weakly in roots. Use of an AtCLCc:GFP fusion revealed localization to the tonoplast. Disruption of the AtCLCc gene by a T-DNA insertion in four independent lines affected physiological responses that are directly related to the movement of chloride across the tonoplast membrane. Opening of clcc stomata was reduced in response to light, and ABA treatment failed to induce their closure, whereas application of KNO 3 but not KCl restored stomatal opening. clcc mutant plants were hypersensitive to NaCl treatment when grown on soil, and to NaCl and KCl in vitro, confirming the chloride dependence of the phenotype. These phenotypes were associated with modifications of chloride content in both guard cells and roots. These data demonstrate that AtCLCc is essential for stomatal movement and salt tolerance by regulating chloride homeostasis.

Systems Dynamic Modeling of a Guard Cell Cl− Channel Mutant Uncovers an Emergent Homeostatic Network Regulating Stomatal Transpiration

“…For example, the tpk1 mutant of Arabidopsis (Arabidopsis thaliana) removes a major pathway for K + flux across the tonoplast and suppresses stomatal closure, yet the mutant has no significant effect on cellular K + content (Gobert et al, 2007). Similarly, the Arabidopsis clcc mutant eliminates the H + -Cl 2 antiporter at the tonoplast; it affects Cl 2 uptake, reduces vacuolar Cl 2 content, and slows stomatal opening; however, counterintuitively, it also suppresses stomatal closure (Jossier et al, 2010). In work leading to this study, we observed that the slac1 anion channel mutant of Arabidopsis paradoxically profoundly alters the activities of the two predominant K + channels at the guard cell plasma membrane.…”

TheArabidopsisNitrate Transporter NRT2.4 Plays a Double Role in Roots and Shoots of Nitrogen-Starved Plants

“…In Arabidopsis thaliana, CLCa and CLCb, both proton-NO 3 -exchangers located in the tonoplast, mediate NO 3 -accumulation in vacuoles (De Angeli et al, 2006;von der Fecht-Bartenbach et al, 2010). Among the other five Arabidopsis CLC proteins, CLCc is involved in chloride transport (Jossier et al, 2010) and CLCd and CLCg possess a selectivity filter in favor of chloride transport (Zifarelli and Pusch, 2009). In Arabidopsis, NRT1 and NRT2 are families of proton-coupled transporters with 53 and seven members, respectively.…”

Transcript, protein and metabolite temporal dynamics in the CAM plant Agave

“…Essential to stomatal activity, the K + flux within guard cells must be counterbalanced by fluxes of anions, such as Cl − . Thus, it was particularly interesting that a member of the chloride channel family (CLC-c) (Aam081659) that is localized to the vacuole and highly expressed in guard cells in Arabidopsis 41 showed reciprocal expression behaviour in Agave compared with that in Arabidopsis. Collectively, the expression patterns we observed provide substantial evidence for the temporal reprogramming of particular genes essential to regulation of stomatal behaviour in an obligate CAM plant.…”