Figure 3.

Tonoplast localization of Ma1β GFP chimera in Nicotiana benthamiana and functional characterization of transporter activity of Ma1β in Xenopus laevis oocytes. A) Ma1β‐GFP and Ma1α‐GFP in isolated vacuoles obtained after lysis of N. benthamiana protoplasts transiently transformed with the GFP fusion constructs. Bars = 20 µm. B) Examples of currents elicited in response to holding potentials ranging from +40 to −180 mV (in 20 mV steps) recorded in control, Ma1β or Ma1α‐expressing cells (25 ng cRNA per cell), either non‐loaded or loaded with malate by microinjecting cells with 50 nL of 100 mm Na‐Malate (increasing cytosolic malate²⁻ concentration by 4.5 mm) 2–3 h prior to the electrophysiological recordings. The red dotted line indicates the zero‐current level. C) Current–voltage (I/V) relationships constructed from steady‐state current recordings with non‐loaded cells such as those shown in (B). Data are mean ± SE. The number of cells recorded: Control (n = 11), Ma1β (n = 16), and Ma1α (n = 8). D) I/V relationships constructed from steady‐state current recordings with malate‐loaded cells such as those shown in (B). Data are mean ± SE. The number of cells recorded: Control (n = 10), Ma1β (n = 13), and Ma1α (n = 8).