Figure 1: Nitrate uptake and reduction in plants with altered NO signalling.

(a) Expression of the NRT marker genes NRT1.1 and NRT2.1 in the roots of WT, nox1 and gsnor1 plants was determined by quantitative reverse transcriptase-PCR (qRT–PCR) and normalized to expression of ACT2. Error bars represent s.d. (n=3). (b) Effect of GSNO on nitrate-induced expression of NRT genes in roots. WT seedlings grown in half-strength MS medium (9.4 mM KNO3 and 10.3 mM NH4NO3) were incubated for 3 h in water with 1 mM nitrate (KNO3), in the absence or presence of GSNO or DEA/NO. NRT expression was determined by qRT–PCR and normalized to expression of ACT2. Error bars represent s.d. (n=3). (c) NR activity and (d) nitrate (NO3−) content determined in leaf extracts of WT plants and genotypes with enhanced (nox1 and gsnor1) or impaired (nia1 nia2 and 35S::FLAG-GSNOR1) (S)NO homeostasis, after 6 hours of light. Data points represent means±s.d. of three independent experiments. Asterisks indicate statistical differences from the WT (Student’s t-test, P<0.05).