Regulation of Root Nitrate Uptake at the NRT2.1 Protein Level in Arabidopsis thaliana

• Published in: The Journal of biological chemistry 2007-08, Vol.282 (32), p.23541-23552
• Main Authors: Wirth, Judith, Chopin, Franck, Santoni, Véronique, Viennois, Gaeölle, Tillard, Pascal, Krapp, Anne, Lejay, Laurence, Daniel-Vedele, Françoise, Gojon, Alain
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Anion Transport Proteins - metabolism; Anion Transport Proteins - physiology; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Arabidopsis Proteins - physiology; Cell Membrane - metabolism; Gene Expression Regulation, Plant; Green Fluorescent Proteins - chemistry; Green Fluorescent Proteins - metabolism; Life Sciences; Microscopy, Confocal; Models, Biological; Molecular Sequence Data; Molecular Weight; Nitrates - metabolism; Plant Roots - metabolism; Plants, Genetically Modified; Protein Structure, Tertiary; Vegetal Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M700901200

In Arabidopsis the NRT2.1 gene encodes a main component of the root high-affinity nitrate uptake system (HATS). Its regulation has been thoroughly studied showing a strong correlation between NRT2.1 expression and HATS activity. Despite its central role in plant nutrition, nothing is known concerning localization and regulation of NRT2.1 at the protein level. By combining a green fluorescent protein fusion strategy and an immunological approach, we show that NRT2.1 is mainly localized in the plasma membrane of root cortical and epidermal cells, and that several forms of the protein seems to co-exist in cell membranes (the monomer and at least one higher molecular weight complex). The monomer is the most abundant form of NRT2.1, and seems to be the one involved in NO3− transport. It strictly requires the NAR2.1 protein to be expressed and addressed at the plasma membrane. No rapid changes in NRT2.1 abundance were observed in response to light, sucrose, or nitrogen treatments that strongly affect both NRT2.1 mRNA level and HATS activity. This suggests the occurrence of post-translational regulatory mechanisms. One such mechanism could correspond to the cleavage of NRT2.1 C terminus, which results in the presence of both intact and truncated proteins in the plasma membrane.