title: Nitrate uptake along the maize primary root: an integrated physiological and molecular approach.
abstract: The spatial variability of the nitrate (NO₃-) uptake along the maize primary root axis was investigated at physiological and molecular levels. Net NO₃- uptake rate (NNUR) and its kinetic parameters, together with the gene expression of a high-affinity NO₃- transporter (NRT2.1), were evaluated. The activity and the expression of plasma membrane H⁺ -ATPase (PM H⁺ -ATPase), key enzyme in plant nutrition, were also analysed. The NNUR showed a heterogeneous spatial pattern along the root, where the regions closer to the root tip early exhibited higher capacity to absorb NO₃- than the basal regions, because of a higher maximum NNUR and faster induction of the inducible high-affinity transport system (iHATS), the presence of the high-affinity transport system (HATS) also at external NO₃- concentrations >100 µm and an improved NO₃- transport because of lower K(m) values. ZmNRT2.1 transcript abundances were not spatially correlated with NNUR, suggesting that post-translational effects or NAR2 protein co-expression could be involved. By contrast, PM H⁺ -ATPase displayed a similar spatial-temporal pattern as that of nitrate uptake, resulting in higher activity in the root tip than in the basal regions. Increased activities of the enzyme after nitrate supply resulted in enhanced expression of MAH3 and MAH4, PM H⁺ -ATPase subfamily II genes, while MAH1 was not expressed.
authors.affiliation: Dipartimento di Biotecnologie per il Monitoraggio Agroalimentare ed Ambientale, Università degli Studi Mediterranea di Reggio Calabria, Salita Melissari, Reggio Calabria, Italy.
authors.forename: Agostino
authors.initials: A
authors.lastname: Sorgonà
authors.forename: Antonio
authors.initials: A
authors.lastname: Lupini
authors.forename: Francesco
authors.initials: F
authors.lastname: Mercati
authors.forename: Luigi
authors.initials: L
authors.lastname: Di Dio
authors.forename: Francesco
authors.initials: F
authors.lastname: Sunseri
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Abenavoli
mesh_terms: D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D009566:Nitrates / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D027321:Anion Transport Proteins; D009566:Nitrates; D010940:Plant Proteins; D020033:Protein Isoforms; D006180:Proton-Translocating ATPases