Figure 5.

CAP1 Modulates Transportation of Ammonium from the Cytoplasm to the Vacuole.

(A) Changes in NH₄⁺ net fluxes of root hair vacuoles (inwards, negative; outwards, positive). Points are data collected every 6 s. Typical net flux traces are shown in the top panel. The NH₄⁺ net fluxes are averaged from MS (n = 17 for wild type, n = 15 for cap1) and MS-NH₄⁺ media (n = 7 for wild type, n = 9 for cap1) and plotted in the bottom panel. Error bars represent means ± se.

(B) Visualizing pHc in root hairs in stable transgenic wild-type and cap1-1 plants with phGFP using ratiometric pH-sensitive GFP. phGFP accumulates in the peripheral cytoplasm regions near the plasma membrane in cap1-1 seedling’s root hair cells grown on MS medium. pH levels were pseudo-color-coded according to the calibrated 410-nm/470-nm ratio image of the same root hair (Supplemental Figure 6). The different phases of root hair development for the wild type and cap1-1 are shown: a, the initial phase; b, transition phase; c, tip growth phase. Bars = 10 µm.

(C) Whole-cell voltage-activated currents in root hair protoplasts of the wild type and cap1-1 mutants. Typical time-dependent currents recorded in root hair cell protoplasts of the wild type (left) and cap1-1 (middle) and NH₄⁺ current-voltage relationships for the wild type (n = 4) and cap1-1 (n = 6) (I-V curve, right) are shown. I-V curves show means ± se.

(D) Effects of NH₄⁺ on whole-cell currents of wild-type and cap1-1 root hairs. The data of NH₄⁺ application to root hair cells by the addition of 150 mM NH₄⁺ to a pipette solution were recorded in the whole-cell patch-clamp configuration (wild type, n = 7; cap1-1, n = 4).