Figure 4.

Nitrate uptake in X. laevis oocytes expressing MtNIP/LATD or mutant Mtnip/latd mRNAs. Oocytes were microinjected with MtNIP/LATD mRNA, mutant mRNA, or water as a negative control, incubated for 3 d, and then placed for the indicated times in medium containing 5 mm or 250 μm nitrate, at pH 5.5, and assayed for nitrate uptake. A, Treatment with 5 mm nitrate. B, Treatment with 250 μm nitrate. C, Treatment with 5 mm nitrate. Oocytes expressing wild-type (WT) MtNIP/LATD (black bars), Mtnip-1 (dark gray bars), Mtnip-3 (horizontally striped bars), Mtlatd (hatched bars), or water as a negative control (gray bars) are shown. Data are shown for one biological replicate ± sd (n = 3–5 batches of 4–6 oocytes per batch). Asterisks mark nitrate uptake that is significantly different from the negative control, using Student’s t test at P < 0.05. Similar results were obtained in more than three repetitions of the experiment.