Fig. 4.

Overexpression of ROXY9 causes the upregulation of the expression of NRT2.1 while overexpression of ROXY15 leads to the downregulation of the expression of NRT2.1. a Expression levels of NRT2.1 in two independent transgenic seedlings overexpressing ROXY9 or ROXY15 (ox) relative to those in the wild type Col-0 seedlings (set to a value of 1). Seven-day-old seedlings grown on complete nutrient medium were used and the expression data were obtained by qRT-PCR. An ACTIN7 was used as a reference gene. Different letters above the bars indicate values that are statistically different (n = 3 biological replicates, P < 0.05; t test). b Expression levels of NRT2.1 in the wild type Col-0 seedlings under nitrate-deficient conditions. Expression levels of NRT2.1 in Col-0 seedlings under nitrate-deficient conditions relative to those in Col-0 seedlings under nitrate-sufficient conditions (set to a value of 1). Six-day-old seedlings were grown on complete nutrient media and transferred to media with either 4 mM nitrate (+N) or no nitrate (-N), and further grown for 6, 12, and 24 h. Then, all seedlings were harvested at the end of the light period (zeitgeber time 16). An ACTIN7 was used as a reference gene. Different letters above the bars indicate values that are statistically different (n = 3 biological replicates, P < 0.05; t test)