Fig. 5.

35S::MIR169a plants are more sensitive to nitrogen (N)-deficiency stress. (a) Overexpression of MIR169a in transgenic Arabidopsis. Small RNA northern blot analysis of miR169a levels in the wild type (WT) and representative transgenic lines was carried out. miR171 is shown as a loading control. (b) N-deficient phenotype of 35S::MIiR169a transgenic plants under hydroponic conditions. Plants were grown hydroponically in a nutrient solution containing 0.5 mM Ca(NO₃)₂ for 5 wk and then transferred to N-free medium for 3 d. Representative pictures are shown. (c) Anthocyanin content in leaves of Col and 35S::miR169a transgenic plants (Col, open bars; #10, stippled bars; #11, hatched bars) with or without N-starvation treatment for 5 d. Error bars represent SE for four independent experiments. *, P < 0.05 (t-test); significant difference from WT. FW, fresh weight. (d) Effects of N deficiency on the growth of transgenic seedlings on agar medium containing 3 mM N (1 mM NH₄NO₃ and 1 mM KNO₃) or 0.3 mM N (0.1 mM NH₄NO₃ and 0.1 mM KNO₃). Seeds were germinated and grown for 10 d. Representative pictures are shown. (e) Chlorophyll content in Col and 35S::miR169a transgenic seedlings (WT, open bars; #10, stippled bars; #11, hatched bars). Error bars represent SE for four independent experiments. *, P < 0.05 (t-test); significant difference from the WT.