Regulation of a putative high‐affinity nitrate transporter (Nrt2;1At) in roots ofArabidopsis thaliana

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Abstract
Summary: Putative high‐affinity nitrate (NO3–) transporter genes, designatedNrt2;1AtandNrt2;2At, were isolated fromArabidopsis thalianaby RT–PCR using degenerate primers. The genes shared 86% and 89% identity at the amino acid and nucleotide levels, respectively, while their proteins shared 30–73% identities with other eukaryotic highaffinity NO3–transporters. Both genes were induced by NO3–, butNrt2;1Atgene expression was not apparent in 2‐ and 5‐day‐old plants. By 10 days, and thereafter,Nrt2;1Atgene expression in roots was substantially higher than for theNrt2;2Atgene. RootNrt2;1Atexpression levels were strongly correlated with inducible high‐affinity13NO3–influx into intact roots under several treatment conditions. The use of inhibitors of N assimilation indicated that downregulation ofNrt2;1Atexpression was mediated by NH4+, gln and other amino acids.