Figure 4.
NRT1.8 Transports Nitrate.
(A) Representative inward currents elicited by 10 mM NO3− at pH 5.5 and a holding potential of −40 mV were recorded for control (top) and NRT1.8 cRNA injected oocytes (bottom).
(B) Quantification of the currents recorded; *P < 0.001, n = 11 for both injected and uninjected oocytes from four separate batches.
(C) High- and low-affinity nitrate uptake activity at pH 5.5. Oocytes were incubated for 3 h with 250 μM or 10 mM nitrate. The amount of nitrate removed from the medium (high-affinity activity) or retained in the oocytes (low-affinity activity) was analyzed by HPLC as described by Huang et al. (1999). *P <0.01, n = 5 samples for both high- and low-affinity uptake assays. Each sample consisted of four oocytes.
(D) NO3− concentration in xylem sap; *P < 0.01, n = 6 separate samples for both Ws and the nrt1.8-1 mutant; each sample pooled sap from approximately nine independent plants. Error bars denote sd in (B) to (D).