Figure 5.

 NRT2.4 Can Transport NO₃^–.

(A) Root ¹⁵NO₃^– influx in the nrt2.1-1 mutant and in ProRolD:NRT2.4 (RolD:2.4) and ProRolD:NRT2.1 (RolD:2.1) overexpressors in the mutant background. Plants were grown on 0.2 mM NO₃^– solution for 43 d. Root ¹⁵NO₃^– influx was measured in complete nutrient solution containing 0.2 mM ¹⁵NO₃^–. The values are means ± sd of five biological replicates. Asterisks indicate statistically significant differences between overexpressors and nrt2.1-1 mutant (P < 0.001). FW, fresh weight.

(B) Uptake of ¹⁵NO₃^– into Xenopus oocytes injected with either water or mRNA mixtures as indicated. Oocytes were incubated for 16 h in ND96 solution at pH 6.5 enriched with 0.5 mM Na ¹⁵NO₃^–. The percentage¹⁵N enrichment values are means ± sd for five oocytes and calculated as described previously (Tong et al., 2005). The asterisk indicates statistically significant differences between mRNA and water-injected oocytes (P < 0.05).