Fig. 4.

Transgenic OsASN1 OX lines showed enhanced tolerance to N limitation at the seedling stage. (A) Phenotypes of OX1, OX2 and WT plants grown. Plants were grown in N-sufficient (10 mM ${\text{NH}}_4^{+}$) or N-limited (0.1 mM ${\text{NH}}_4^{+}$) media for 8 d. Scale bars = 2.5 cm. Measurement of the height (B) and fresh weight (C) of WT and OX seedlings. (D) N concentrations in shoots and roots of WT and OX plants. (E, F) N uptake analysis of WT and OX1 seedlings grown in Yoshida solution. Seven-day-old seedlings were treated with ¹⁵N-labeled NH4Cl, and ¹⁵N contents of roots (E) and shoots (F) were measured at the indicated time points after treatment. Expression analysis of OsAMT1;1 (G), OsAMT1;2 (H), OsAMT1;3 (I), OsGS1;1 (J), OsNADH-GOGAT1 (K) and OsASN2 (L) in WT and OX1 plants using qRT-PCR. Data represent mean ± SE of five biological replicates. Significant differences between WT and OX plants were determined using Student’s t-test and are indicated with an asterisk (*P < 0.05). S, shoots of plants grown in N-sufficient medium; NS, shoots of plants grown in N-limited medium; R, roots of plants grown in N-sufficient medium; NR, roots of plants grown in N-limited medium.