Potassium Transporter KUP7 Is Involved in K+ Acquisition and Translocation in Arabidopsis Root under K+-Limited Conditions  Min Han, Wei Wu, Wei-Hua Wu, Yi Wang  Molecular Plant  Volume 9, Issue 3, Pages 437-446 (March 2016) DOI: 10.1016/j.molp.2016.01.012 Copyright © 2016 The Authors Terms and Conditions

Figure 1 kup7 Mutant Is Sensitive to Low-K+ Stress. (A) Structure of KUP7 gene. The black boxes indicate exons and the lines represent introns. The T-DNA insertion site in kup7 mutant is shown by a triangle. (B) RT–PCR analysis of KUP7 expression in kup7 mutant and wild-type plants (Col). The primers used in the RT–PCR experiment are shown in (A) using arrows (F, forward; R, reverse). (C–E) Chlorosis symptom (C and D) and chlorophyll content (E) of wild-type plants (Col) and kup7 mutant after being grown on MS or LK medium for 10 days. The data in (E) are shown as means ± SE (n = 3). The Student t-test (*p < 0.05) was used to analyze the statistical significance. (F) Phenotype test of wild-type plants (Col) and kup7 mutant after being grown on medium containing different K+ concentrations for 10 days. Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 2 Complementation Lines Rescue the Low-K+ Sensitive Phenotype of kup7 Mutant. (A) Real-time PCR analysis of KUP7 expression in wild-type plants (Col), kup7 mutant, and complementation lines (COM1 and COM2). (B–E) Chlorosis symptom (B and C), chlorophyll content (D), and K+ content (E) of wild-type plants (Col), kup7 mutant, and complementation lines (COM1 and COM2) after being grown on MS or LK medium for 10 days. Data in (D) and (E) are shown as means ± SE (n = 3). The Student t-test (*p < 0.05) was used to analyze the statistical significance. Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 3 KUP7 Mediates K+ Transport in Yeast. (A) KUP7 and AKT1 complement the K+ uptake-deficient yeast mutant R5421 on AP medium containing different K+ concentrations. Yeast strain R757 was used as positive control. (B) K+ transport activity of KUP7 in yeast is inhibited by external NH4+. The liquid AP medium contained 1 mM K+ and different NH4+ (0 and 10 mM). The data points are shown as means ± SE (n = 3). Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 4 KUP7 Is Localized at the Plasma Membrane. The KUP7-GFP transgenic Arabidopsis plants were used for the detection of KUP7 localization. The plants transformed with GFP empty vector was used as control. Arabidopsis seeds were germinated on 1/2 MS medium. Then the root hairs of 5-day-old seedlings were used for the GFP fluorescence observation. The plasma membrane (PM) and tonoplast (TP) are indicated by arrowheads. Red arrows were drawn to calculate the fluorescence intensities. The fluorescence intensities along with the red arrows were shown below the pictures. Top panels, bright-field images; middle panels, GFP images; bottom panels, fluorescence intensities of the arrow-covered regions. Scale bars, 10 μm. Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 5 KUP7 Is Ubiquitously Expressed in Arabidopsis. Expression pattern of KUP7 determined in ProKUP7-1:GUS transgenic Arabidopsis plants. (A) GUS staining of 5-day-old seedling. (B and C) GUS staining of mature root (B) and primary root tip (C) of 7-day-old seedling. Scale bars, 50 μm. (D–G) Expression pattern of KUP7 in leaf (D), stem (E), flower (F), and silique (G). Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 6 K+ Uptake in kup7 Mutant Is Impaired under K+-Deficient Conditions. (A) Total K+ amount of various plants after grown on MS or LK medium for 10 days. Data are shown as means ± SE (n = 3). The Student t-test (*p < 0.05) was used to analyze the statistical significance. (B) K+ uptake ability comparison of various plants using K+-depletion assay. Data are shown as means ± SE (n = 4). The Student t-test (*p < 0.05) was used to analyze the statistical significance. Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions

Figure 7 kup7 Mutant Is Defective in K+ Translocation from Root to Shoot under K+-Deficient Conditions. (A) K+ concentration in xylem sap from various plants grown in nutrient solution containing different K+ concentrations (5 mM and 100 μM). Data are shown as means ± SE (n = 3). The Student t-test (*p < 0.05) was used to analyze the statistical significance. (B) K+ concentration in xylem sap is dependent on external K+ concentrations in nutrient solution. Data are shown as means ± SE (n = 3). The Student t-test (*p < 0.05) was used to analyze the statistical significance. Molecular Plant 2016 9, 437-446DOI: (10.1016/j.molp.2016.01.012) Copyright © 2016 The Authors Terms and Conditions