Nitrogen affects cluster root formation and expression of putative peptide transporters

• Published in: Journal of experimental botany 2009-07, Vol.60 (9), p.2665-2676
• Main Authors: Paungfoo-Lonhienne, Chanyarat, Schenk, Peer M, Lonhienne, Thierry G.A, Brackin, Richard, Meier, Stefan, Rentsch, Doris, Schmidt, Susanne
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell membranes; Cluster root; Complementary DNA; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; heathland; Heathlands; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Molecular Sequence Data; Multigene Family; Nitrogen; Nitrogen - metabolism; organic nitrogen; peptide transporters; Peptides - metabolism; Plant nutrition; Plant Proteins - genetics; Plant Proteins - metabolism; Plant roots; Plant Roots - enzymology; Plant Roots - genetics; Plant Roots - growth & development; Plants; Proteaceae; Proteaceae - enzymology; Proteaceae - genetics; Proteaceae - growth & development; Protein Transport; Protoplasts; RESEARCH PAPER; Research Papers; roots; Seedlings; Yeasts
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erp111

Non-mycorrhizal Hakea actites (Proteaceae) grows in heathland where organic nitrogen (ON) dominates the soil nitrogen (N) pool. Hakea actites uses ON for growth, but the role of cluster roots in ON acquisition is unknown. The aim of the present study was to ascertain how N form and concentration affect cluster root formation and expression of peptide transporters. Hydroponically grown plants produced most biomass with low molecular weight ON>inorganic N>high molecular weight ON, while cluster roots were formed in the order no-N>ON>inorganic N. Intact dipeptide was transported into roots and metabolized, suggesting a role for the peptide transporter (PTR) for uptake and transport of peptides. HaPTR4, a member of subgroup II of the NRT1/PTR transporter family, which contains most characterized di- and tripeptide transporters in plants, facilitated transport of di- and tripeptides when expressed in yeast. No transport activity was demonstrated for HaPTR5 and HaPTR12, most similar to less well characterized transporters in subgroup III. The results provide further evidence that subgroup II of the NRT1/PTR family contains functional di- and tripeptide transporters. Green fluorescent protein fusion proteins of HaPTR4 and HaPTR12 localized to tonoplast, and plasma- and endomembranes, respectively, while HaPTR5 localized to vesicles of unknown identity. Grown in heathland or hydroponic culture with limiting N supply or starved of nutrients, HaPTR genes had the highest expression in cluster roots and non-cluster roots, and leaf expression increased upon re-supply of ON. It is concluded that formation of cluster roots and expression of PTR are regulated in response to N supply.