Figure 11.

Decreased Nitrate Concentration in nrt1.5 Xylem Sap.

(A) Schematic representation of two allelic T-DNA insertion lines nrt1.5-3 (SAIL_72_F04) and nrt1.5-4 (SALK_063393) were PCR screened and sequenced as described (Krysan et al., 1999) to identify homozygous mutants.

(B) RT-PCR did not detect intact NRT1.5 mRNA in nrt1.5-3 (left) and nrt1.5-4 (right) mutant plants.

(C) The homozygous mutants and wild-type Columbia-0 were grown hydroponically for 4 weeks, subjected to nitrate starvation for 7 d, and then transferred to medium with 2.2, 5, or 10 mM nitrate for 12 h. Xylem sap was collected for 6 h, and nitrate concentrations were determined as described in Methods. Values are mean ± sd, n = 5, and the asterisk indicates significant differences between wild-type Columbia-0 and the two mutant lines at P < 0.01.