Transcription Factor Controls Ammonium Uptake by Inducing Ammonium Transporters in Rice Roots.

Nitrogen is one of the most important mineral elements for plant growth. We studied the functional roles of () in controlling ammonium uptake. The growth of null mutants of was retarded in a medium containing ammonium as the sole nitrogen source. In contrast, those mutants grew normally in a medium with nitrate as the sole nitrogen source. The gene expression was induced by ammonium but not by nitrate. Uptake of ammonium was lower in mutants than in the wild type, while that of nitrate was not affected by the mutation. This indicated that OsDOF18 is involved in regulating ammonium transport. Among the 10 ammonium transporter genes examined here, expression of , , , and was reduced in mutants, demonstrating that the ammonium transporter genes function downstream of . Genes for nitrogen assimilation were also affected in the mutants. These results provide evidence that mediates ammonium transport and nitrogen distribution, which then affects nitrogen use efficiency.