Xue S , Yao X , Luo W , Jha D , Tester M , Horie T , Schroeder JI .

P42 ES010337 NIEHS NIH HHS

	Figure 1. Fluorescence labeling of root stelar cells in enhancer trap (E2586) plants.A) RT-PCR analysis of expression level of AtHKT1;1 gene in E2586 (a) and athkt1;1-4 X E2586 (b) plants. B) GFP-marked stele in root (a–c, f–h) and root stelar cell protoplasts (d, e, i and j). E2586 (a–e) and athkt1;1-4 X E2586 (f–j). (a, d, f, i): bright field; (b, e, g, j): fluorescence images; (c): merged graphs (a) and (b); (h): merged graphs (f) and (g).
	Figure 2. HKT1;1-mediated Na+ currents in E2586 wild-type (WT) and lack thereof in athkt1;1-4 GFP-labeled root stelar cell protoplasts.A) Typical whole-cell currents activated by rapid voltage ramps (5 mV ms−1, +99 to −141 mV) with the bath solution containing 0 (grey trace) or 50 mM NaCl (black trace) in wild-type E2586 root stelar cell protoplasts. B) Average current-voltage relationships recorded as in (A) from five wild-type E2586 protoplasts. Filled circles and open circles represent 0 mM and 50 mM NaCl in the bath respectively. The data are mean ± SE. The average current of −59 pA activated at a voltage of −140 mV corresponds to a current density of −35 mA m−2 with an average protoplast diameter of 23 µm. C) Typical whole-cell recordings using the same voltage ramps as in (A) with the bath solution containing 0 (grey trace) or 50 mM NaCl (black trace) in athkt1;1-4 loss-of-function mutant root stelar cell protoplasts. D) Average current-voltage relationships recorded as in (C) from five athkt1;1-4 mutant protoplasts. Filled circles and open circles represent 0 mM and 50 mM NaCl in the bath respectively. The data are mean ± SE. The bath solution contained 0/50 mM NaCl, 2 mM CaCl2, 5 mM MES, pH 5.7 adjusted with Tris. The pipette solution contained 50 mM NaCl, 1.3 mM CaCl2, 3 mM EGTA, 5 mM HEPES, pH 7.2 adjusted with Tris. The osmolalities of bath and pipette solutions were adjusted to 290–300 mmol·Kg−1 with D-mannitol. Liquid junction potential (LJP) was +0.3 mV for 50 mM [Na+]o and −12 mV for 0 mM [Na+]o (calculated by Clampex 10) and was corrected in (A–D).
	Figure 3. AtHKT1;1 mediates Na+ currents.A) Whole-cell current recorded with 50 mM NaCl in both the bath and pipette solutions in wild-type root stelar cells. B) Average current-voltage relationships recorded as in (A) from five protoplasts. Liquid junction potential (LJP) in (A and B) was +0.3 mV (calculated by Clampex 10) and was corrected in (A) and (B). C) Whole-cell current recorded with 5 mM NaCl in the pipette solution and 50 mM NaCl in the bath solution. D) Average current-voltage relationships recorded as in (C) from five protoplasts. LJP in (C and D) was +8 mV (calculated by Clampex 10) and was corrected in (C) and (D). ENa+: Na+ equilibrium potential. ECl−: Cl− equilibrium potential. The data in (B and D) are mean ± SE. The average currents of −19 and −35 pA activated at a voltage of −80 mV correspond to current densities of −11 and −21 mA m−2 with an average protoplast diameter of 23 µm. The bath solution in (A) to (D) contained 50 mM NaCl, 2 mM CaCl2, 5 mM MES, pH 5.7 adjusted with Tris. The pipette solution in (A) and (B) contained 50 mM NaCl, 1.3 mM CaCl2, 3 mM EGTA, 5 mM HEPES, pH 7.2 adjusted with Tris. The pipette solution in (C) and (D) contained 5 mM NaCl, 1.3 mM CaCl2, 3 mM EGTA, 5 mM HEPES, pH 7.2 adjusted with Tris. The osmolalities of bath and pipette solutions were adjusted to 290–300 mmol·Kg−1 with D-mannitol.
	Figure 4. Removal of extracellular Na+ in AtHKT1;1 expressing Xenopus oocytes reduces AtHKT1;1-mediated outward currents.Recordings were carried out 1 to 2 days after AtHKT1;1 cRNA injection (source: Columbia ecotype). Oocytes were clamped in perfusion solutions containing either 0 mM NaCl or 50 mM NaCl. Applied membrane potentials ranged from +110 to −150 mV. Mean steady-state currents (±SEM) recorded in oocytes injected with either 20 ng of Col-0 wild-type AtHKT1;1 (n = 8) cRNA, or with H2O (n = 13) as control.
	Figure 5. Potassium currents in wild-type (WT-E2586) and athkt1;1-4 root stelar cell protoplasts are indistinguishable.A) Whole-cell currents activated by voltage ramps (5 mVms−1, +99 to −141 mV) with 5 mM KCl in the pipette solution and 50 mM KCl in the bath solution in wild-type (black trace) and athkt1;1-4 mutant (red trace) root stelar cells. B) Average current-voltage relationships recorded as in (A) from five athkt1;1-4 mutant protoplasts (open circles), five WT (E2586) protoplasts (filled circles). Average currents of −53 and −56 pA activated at a voltage of −141 mV correspond to current densities of −32 and −34 mA m−2 with an average protoplast diameter of 23 µm. The bath solution contained 50 mM KCl, 2 mM CaCl2, 5 mM MES, pH 5.7 adjusted with Tris. The pipette solution contained 5 mM KCl, 1.3 mM CaCl2, 3 mM EGTA, 5 mM HEPES, pH 7.2 adjusted with Tris. The osmolalities of bath and pipette solutions were adjusted to 290–300 mmol·Kg−1 with D-mannitol. Liquid junction potential (LJP) in (A and B) was +0.7 mV (calculated by Clampex 10) and was corrected in (A) and (B).

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