Figure 4.

Auxin promotes the expression of N metabolism-related genes, and ${\text{NO}}_3^{-}$ uptake is mediated by OsARFs. (A) ¹⁵${\text{NO}}_3^{-}$ uptake rate in the roots of two-week-old plants under mock and external IAA treatment (1 μM). P-values were generated from two-sided Student’s t tests. Data are mean ± sem (n = 3). (B, C) mRNA abundance of OsARF6 and OsARF17 in roots under IAA treatment relative to the control (set to 1). P-values were generated from two-sided Student’s t tests. Data are mean ± sem (n = 3). (D) mRNA abundance in roots and shoots under IAA treatment relative to the control (set to 1). ^** indicates the least significant difference at 0.01 probability level, generated from Student’s t tests. Data are mean ± sem (n = 3). (E, F) Extent of OsARF6 and OsARF17-mediated ChIP-qPCR enrichment (relative to Input) of TGTCTC-containing promoter fragments from OsNRT1.1B (fragment 1; shown in Figure 3, I and J). P-values were generated from two-sided Student’s t-tests. Data are mean ± sem (n = 3). (G) ¹⁵${\text{NO}}_3^{-}$ uptake rate in the roots of ZH11, osarf6, and osarf17 plants under mock and external IAA treatment (1 μM). Different letters denote significant differences (P < 0.05) from Duncan’s multiple range test. Data are mean ± sem (n = 3). (H) ¹⁵${\text{NO}}_3^{-}$ uptake rate in the roots of OsARF6 and OsARF17 overexpression lines in the ZH11 pAct:DNR1-Flag-1 background. Different letters denote significant differences (P < 0.05) from Duncan’s multiple range test. Data are mean ± sem (n = 6).