Fig. 6.

High nitrate availability promotes the accumulation of DELLA proteins and the induction of the downstream targets GNC and CGA1/GNL, triggering the up-regulation of SMZ and SNZ transcript levels. Representative confocal images showing roots of 7-d-old Arabidopsis RGA::GFP-RGA seedlings grown on agar plates in N-free nutrient medium supplemented with either 1 mM or 3 mM KNO₃ (A). Quantification of the relative number of nuclei with specific GFP intensities (n=6) (B). Relative RNA levels for GNC and CGA1/GNL (C). Plants were grown on agar plates in N-free nutrient medium supplemented with either 1 mM (light gray) or 3 mM (dark gray) KNO₃. At the days indicated, plants were harvested and RNA was extracted and used as a template for qRT-PCR. (D) Relative levels of SMZ and SNZ. Plants were grown on Petri plates containing solid N-free nutrient medium supplemented with 3 mM KNO₃. On day 9, plants were harvested, their RNA was extracted and subsequently used for qRT-PCR. The ADAPTOR PROTEIN-4 MU-ADAPTIN gene (At4g24550) was used as a housekeeping gene. GNCox, GNC overexpressor plants; GNLox, CGA/GNL overexpressor plants; gnc-gnl, gnc-cga/gnl double-mutant plants. Data are means and SE for three independent biological replicates of 15 plants. Asterisks highlight significant differences as determined by Student’s t-test (P≤0.05). Different letters highlight significant differences as determined by Tukey’s Multiple Comparison test (P ≤0.05).