• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of pnasPNASInfo for AuthorsSubscriptionsAboutThis Article
Proc Natl Acad Sci U S A. Jul 23, 1996; 93(15): 8139–8144.

Preferential expression of an ammonium transporter and of two putative nitrate transporters in root hairs of tomato.


Root hairs as specialized epidermal cells represent part of the outermost interface between a plant and its soil environment. They make up to 70% of the root surface and, therefore, are likely to contribute significantly to nutrient uptake. To study uptake systems for mineral nitrogen, three genes homologous to Arabidopsis nitrate and ammonium transporters (AtNrt1 and AtAmt1) were isolated from a root hair-specific tomato cDNA library. Accumulation of LeNrt1-1, LeNrt1-2, and LeAmt1 transcripts was root-specific, with no detectable transcripts in stems or leaves. Expression was root cell type-specific and regulated by nitrogen availability. LeNrt1-2 mRNA accumulation was restricted to root hairs that had been exposed to nitrate. In contrast, LeNrt1-1 transcripts were detected in root hairs as well as other root tissues under all nitrogen treatments applied. Analogous to LeNrt1-1, the gene LeAmt1 was expressed under all nitrogen conditions tested, and root hair-specific mRNA accumulation was highest following exposure to ammonium. Expression of LeAMT1 in an ammonium uptake-deficient yeast strain restored growth on low ammonium medium, confirming its involvement in ammonium transport. Root hair specificity and characteristics of substrate regulation suggest an important role of the three genes in uptake of mineral nitrogen.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (2.1M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Bloom AJ, Sukrapanna SS, Warner RL. Root respiration associated with ammonium and nitrate absorption and assimilation by barley. Plant Physiol. 1992 Aug;99(4):1294–1301. [PMC free article] [PubMed]
  • Aslam M, Travis RL, Huffaker RC. Comparative kinetics and reciprocal inhibition of nitrate and nitrite uptake in roots of uninduced and induced barley (Hordeum vulgare L.) seedlings. Plant Physiol. 1992;99:1124–1133. [PMC free article] [PubMed]
  • Siddiqi MY, Glass AD, Ruth TJ, Rufty TW. Studies of the Uptake of Nitrate in Barley: I. Kinetics of NO(3) Influx. Plant Physiol. 1990 Aug;93(4):1426–1432. [PMC free article] [PubMed]
  • Wang MY, Siddiqi MY, Ruth TJ, Glass ADM. Ammonium Uptake by Rice Roots (II. Kinetics of 13NH4+ Influx across the Plasmalemma). Plant Physiol. 1993 Dec;103(4):1259–1267. [PMC free article] [PubMed]
  • Raper CD, Jr, Vessey JK, Henry LT, Chaillou S. Cyclic variations in nitrogen uptake rate of soybean plants: effects of pH and mixed nitrogen sources. Plant Physiol Biochem. 1991;29(3):205–212. [PubMed]
  • Vessey JK, York EK, Henry LT, Raper CD., Jr Uniformity of environmental conditions and plant growth in a hydroponic culture system for use in a growth room with aerial CO2 control. Biotronics. 1988;17:79–94. [PubMed]
  • Bloom AJ, Chapin FS. Differences in steady-state net ammonium and nitrate influx by cold- and warm-adapted barley varieties. Plant Physiol. 1981 Nov;68(5):1064–1067. [PMC free article] [PubMed]
  • Imsande J, Touraine B. N Demand and the Regulation of Nitrate Uptake. Plant Physiol. 1994 May;105(1):3–7. [PMC free article] [PubMed]
  • Henriksen GH, Raman DR, Walker LP, Spanswick RM. Measurement of Net Fluxes of Ammonium and Nitrate at the Surface of Barley Roots Using Ion-Selective Microelectrodes : II. Patterns of Uptake Along the Root Axis and Evaluation of the Microelectrode Flux Estimation Technique. Plant Physiol. 1992 Jun;99(2):734–747. [PMC free article] [PubMed]
  • Lazof DB, Rufty TW, Redinbaugh MG. Localization of Nitrate Absorption and Translocation within Morphological Regions of the Corn Root. Plant Physiol. 1992 Nov;100(3):1251–1258. [PMC free article] [PubMed]
  • Crawford NM. Nitrate: nutrient and signal for plant growth. Plant Cell. 1995 Jul;7(7):859–868. [PMC free article] [PubMed]
  • Tsay YF, Schroeder JI, Feldmann KA, Crawford NM. The herbicide sensitivity gene CHL1 of Arabidopsis encodes a nitrate-inducible nitrate transporter. Cell. 1993 Mar 12;72(5):705–713. [PubMed]
  • Marini AM, Vissers S, Urrestarazu A, André B. Cloning and expression of the MEP1 gene encoding an ammonium transporter in Saccharomyces cerevisiae. EMBO J. 1994 Aug 1;13(15):3456–3463. [PMC free article] [PubMed]
  • Ninnemann O, Jauniaux JC, Frommer WB. Identification of a high affinity NH4+ transporter from plants. EMBO J. 1994 Aug 1;13(15):3464–3471. [PMC free article] [PubMed]
  • Steiner HY, Song W, Zhang L, Naider F, Becker JM, Stacey G. An Arabidopsis peptide transporter is a member of a new class of membrane transport proteins. Plant Cell. 1994 Sep;6(9):1289–1299. [PMC free article] [PubMed]
  • Rentsch D, Laloi M, Rouhara I, Schmelzer E, Delrot S, Frommer WB. NTR1 encodes a high affinity oligopeptide transporter in Arabidopsis. FEBS Lett. 1995 Aug 21;370(3):264–268. [PubMed]
  • Padgett PE, Leonard RT. Contamination of Ammonium-Based Nutrient Solutions by Nitrifying Organisms and the Conversion of Ammonium to Nitrate. Plant Physiol. 1993 Jan;101(1):141–146. [PMC free article] [PubMed]
  • Zobel RW, Del Tredici P, Torrey JG. Method for growing plants aeroponically. Plant Physiol. 1976 Mar;57(3):344–346. [PMC free article] [PubMed]
  • Goyal SS, Huffaker RC. The uptake of NO3-, NO2-, and NH4+ by intact wheat (Triticum aestivum) seedlings. I. Induction and kinetics of transport systems. Plant Physiol. 1986;82:1051–1056. [PMC free article] [PubMed]
  • Siddiqi MY, Glass AD, Ruth TJ, Fernando M. Studies of the Regulation of Nitrate Influx by Barley Seedlings Using NO(3). Plant Physiol. 1989 Jul;90(3):806–813. [PMC free article] [PubMed]
  • Kosola KR, Bloom AJ. Methylammonium as a Transport Analog for Ammonium in Tomato (Lycopersicon esculentum L.). Plant Physiol. 1994 May;105(1):435–442. [PMC free article] [PubMed]
  • Franco AR, Cárdenas J, Fernández E. Two different carriers transport both ammonium and methylammonium in Chlamydomonas reinhardtii. J Biol Chem. 1988 Oct 5;263(28):14039–14043. [PubMed]
  • Dubois E, Grenson M. Methylamine/ammonia uptake systems in saocharomyces cerevisiae: multiplicity and regulation. Mol Gen Genet. 1979 Aug;175(1):67–76. [PubMed]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


  • Compound
    PubChem Compound links
  • MedGen
    Related information in MedGen
  • Nucleotide
    Published Nucleotide sequences
  • Pathways + GO
    Pathways + GO
    Pathways, annotations and biological systems (BioSystems) that cite the current article.
  • Protein
    Published protein sequences
  • PubMed
    PubMed citations for these articles
  • Substance
    PubChem Substance links
  • Taxonomy
    Related taxonomy entry
  • Taxonomy Tree
    Taxonomy Tree

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...