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Results: 5

1.
Fig. 1.

Fig. 1. From: A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.

Currents generated by AtHKT1;1 or OsHKT2;4 expressed in the Xenopus oocytes. (A) Time dependency and activation kinetics in the currents generated by OsHKT2;4. (Left) Typical whole-cell currents recorded by hyperpolarized pulses from the oocytes injected with water (“Control”) or oocytes expressing AtHKT1;1 (AtHKT1;1) or OsHKT2;4 (OsHKT2;4) perfused with the bath solution containing (in mM) 0.3 K–gluconate, 10 Na–gluconate, 6 MgCl2, 1.8 CaCl2, 185 mannitol, and 10 Mes–Tris. Dotted lines represent the zero current level. The current–voltage relationships were deduced from 15 cells under each condition and presented on the right. (B) (Left) Traces show the typical tail currents generated by the control oocytes or oocytes expressing AtHKT1;1 or OsHKT2;4 recorded with the deactivation protocol. (Right) The current–voltage relationships were deduced from 12 cells/condition.

Wen-Zhi Lan, et al. Proc Natl Acad Sci U S A. 2010 April 13;107(15):7089-7094.
2.
Fig. 2.

Fig. 2. From: A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.

Ca2+ determines the kinetics of OsHKT2;4 currents. (A) Ca2+ induced the time dependency and large magnitude in the current recorded by hyperpolarized pulses. The typical current traces were generated by the oocytes expressing OsHKT2;4 perfused with various ions (Left). The mean current data were deduced from the recordings of the control oocytes and the oocytes expressing OsHKT2;4 perfused by the buffer solution containing (in mM) 10 Na+ + 0.3 K+ + 6 Mg2+, 10 Na+ + 0.3 K+ + 6 Mg2+ + 1.8 Ca2+, or 1.8 Ca2+ (Right). (B) Unique tail currents induced by Ca2+. (Left) Traces show the typical tail currents generated by oocytes expressing OsHKT2;4 perfused with various ions. (Right) The mean tail currents were summarized from recordings of the oocytes expressing OsHKT2;4 perfused with the solution containing (in mM) 10 Na+, 0.3 K+, 6 Mg2+, and 1.8 Ca2+, 10 Na+ + 0.3 K+ + 6 Mg2+, or 10 Na+ + 0.3 K+ + 6 Mg2+ + 1.8 Ca2+. (C) The OsHKT2;4 current was sensitive to extracellular Ca2+ concentration. (Left) The typical current traces were recorded at −120 mV from the control oocyte and the oocyte expressing AtHKT1;1 or OsHKT2;4 perfused with a solution containing (in mM) 185 mannitol and 10 Mes–Tris (pH 7.4) with 0, 0.3, or 10 Ca2+. (Right) The current–voltage relationship was deduced from recordings of the oocytes expressing OsHKT2;4. Summarized current data are from 10 cells/condition.

Wen-Zhi Lan, et al. Proc Natl Acad Sci U S A. 2010 April 13;107(15):7089-7094.
3.
Fig. 5.

Fig. 5. From: A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.

Expression pattern and subcellular localization of OsHKT2;4 protein. (A) Expression of OsHKT2;4 analyzed using RT–PCR in various organs of the Nipponbare plant. Ubiquitin was used as a control. S, spikelet; L, leaf; LS, leaf sheath; IN, internode; N, node; BS, base of stem; R, root. (B) In OsHKT2;4 promoter–GUS transgenic plants, GUS was expressed in spikelets (a), leaves (d and f), leaf sheaths (f), nodes (j and k), internodes (k), primary roots (m) and lateral roots (g and l), cross-sections of leaves (b), main veins of leaves (c), leaf sheaths (e), nodes (i), base of stems (n), primary roots (h), and lateral roots (h). E, epidermis; M, mesophyll; X, xylem; P, phloem. (Scale bars: c, e, and h—20 μm; b, i, l, m, and n—50 μm.) (C) Immunogold localization of the OsHKT2;4 protein to the plasma membrane of root hair cells. b and c are enlarged sections of a. Arrows indicate gold particles. RH, root hair; Ep, epidermis; En, endodermis; C, cortex; CW, cell wall. (Scale bars: a, 10 μm; b and c, 1 μm.)

Wen-Zhi Lan, et al. Proc Natl Acad Sci U S A. 2010 April 13;107(15):7089-7094.
4.
Fig. 3.

Fig. 3. From: A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.

OsHKT2;4 expression facilitates Ca2+ accumulation in Xenopus oocytes. (A) The hyperpolarized pulses produced the same current in the OsHKT2;4-injected oocytes perfused by different Ca2+ salts (Left). But the tail current recorded under voltage steps of 55 to −95 mV following a prepulse at −120 mV was dependent on the anions in the Ca2+ salts (Right). The oocytes were perfused with a solution containing (in mM) 185 mannitol and 10 Mes–Tris with 10 CaCl2, CaI2, Ca (gluconate)2, or Ca(NO3)2. (B) The current–voltage relationship was deduced from currents recorded by hyperpolarized pulses (Left) or by deactivation protocol (Right), respectively. The oocytes were perfused with a solution containing (in mM) 185 mannitol and 10 Mes–Tris with 5 EGTA–Na4, 1.8 CaCl2, or 1.8 CaCl2 + 5 EGTA. (C) OsHKT2;4-injected oocytes uptake more Ca2+ than control oocytes. (Left) The time course of 45Ca2+ accumulation in oocytes bathed in 1.8 mM CaCl2. (Right) The concentration-dependent 45Ca2+ accumulation in the oocytes incubated for 10 min in a solution containing 0, 0.3, 1.8, 5, 10, or 20 mM CaCl2. (D) The typical traces of the currents recorded by hyperpolarized pulses (i) or the tail currents (ii) in OsHKT2;4-injected oocytes perfused with the solution containing (in mM) 10 CaCl2 or 10 CaCl2 + 0.1 NPPB. (iii) The current–voltage relationship was deduced from the tail current recorded from OsHKT2;4-injected oocytes perfused with the same solution containing various inhibitors, including 0.1 mM of DIDS, NFA, NPPB, or tamoxifen. Summarized Ca2+ uptake was deduced from results of 50 oocytes/condition repeated in three separate experiments, and the current data are from 10 cells/condition.

Wen-Zhi Lan, et al. Proc Natl Acad Sci U S A. 2010 April 13;107(15):7089-7094.
5.
Fig. 4.

Fig. 4. From: A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel.

OsHKT2;4 functions as a nonselective cation channel with multiple pathways. (A) OsHKT2;4 expressed in the oocytes was permeable to a broad range of cations. (i) The currents at −150 mV recorded from the control oocytes or the oocytes expressing AtHKT1;1 or OsHKT2;4 perfused with a solution containing 185 mM mannitol, 10 mM Mes–Tris (“Buffer”), or the same “Buffer” with 10 mM NH4+, Li+, Na+, K+, or Cs+. (ii) The mean current at −150 mV recorded from the control oocytes or the oocytes expressing OsHKT2;4 perfused with the same “Buffer” containing 10 mM Ca2+, Mg2+, Zn2+, Mn2+, Cu2+, Fe2+, or Cd2+. (iii) The mean currents at −150 mV recorded from the oocytes expressing OsHKT2;4 perfused with the “Buffer” or Buffer plus 1 mM La3+, Gd3+, or Al3+. (B) The activity of OsHKT2;4 was inhibited by the channel blockers. (i) The mean current at −150 mV recorded from the oocytes expressing OsHKT2;4 perfused with a “Buffer” containing (in mM) 10 K+ + 1 La3+, 10 K+ + 1 Gd3+, 10 K+ + 1 Ba2+, 10 Na+, 10 Na+ + 1 La3+, 10 K+ + 1 Ba2+, 10 Mg2+, 10 Mg2+ + 1 Ba2+, or 10 Mg2+ + 1 La3+. (ii) The mean current at −150 mV recorded with control oocytes or oocytes expressing OsHKT2;4 perfused with a “Buffer” containing either 1.8 or 10 mM Ca2+ in the presence or absence of 1 mM indicated blocker. (iii) 45Ca2+ accumulation in control oocytes expressing OsHKT2;4, incubated in a “Buffer” with (in mM) 10 Ca2+, 10 Ca2+ + 1 La3+ or 10 Ca2++ 1 Gd3+ for 10 min. The relative 45Ca2+ content in the oocytes was calculated as the ratio of 45Ca2+ accumulation in the OsHKT2;4-injected oocytes over control oocytes in the presence of 10 mM Ca2+. (C) OsHKT2;4 activity recorded from excised inside-out patches of the oocytes. (Left) Representative currents in an excised inside-out patch recorded at membrane potentials of 110, 130, or 150 mV. The horizontal line represents the zero current level. (Right) Current–voltage relationship of currents from excised inside-out patches. Summarized Ca2+ uptake was deduced from results of 50 oocytes/condition repeated in three separate experiments, and the current recording data are from 10 cells/condition.

Wen-Zhi Lan, et al. Proc Natl Acad Sci U S A. 2010 April 13;107(15):7089-7094.

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