Acquisition and assimilation of nitrogen as peptide-bound and D-enantiomers of amino acids by wheat

Paul W. Hill, Richard S. Quilliam, Thomas H. DeLuca, John Farrar, Mark Farrell, Paula Roberts, Kevin K. Newsham, David W. Hopkins, Richard D. Bardgett, David L. Jones

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    Abstract

    Nitrogen is a key regulator of primary productivity in many terrestrial ecosystems. Historically, only inorganic N (NH4+ and NO3-) and L-amino acids have been considered to be important to the N nutrition of terrestrial plants. However, amino acids are also present in soil as small peptides and in D-enantiomeric form. We compared the uptake and assimilation of N as free amino acid and short homopeptide in both L- and D-enantiomeric forms. Sterile roots of wheat (Triticum aestivum L.) plants were exposed to solutions containing either 14C-labelled L-alanine, D-alanine, L-trialanine or D-trialanine at a concentration likely to be found in soil solution (10 µM). Over 5 h, plants took up L-alanine, D-alanine and L-trialanine at rates of 0.9±0.3, 0.3±0.06 and 0.3±0.04 µmol g-1 root DW h-1, respectively. The rate of N uptake as L-trialanine was the same as that as L-alanine. Plants lost ca.60% of amino acid C taken up in respiration, regardless of the enantiomeric form, but more (ca.80%) of the L-trialanine C than amino acid C was respired. When supplied in solutions of mixed N form, N uptake as D-alanine was ca.5-fold faster than as NO3-, but slower than as L-alanine, L-trialanine and NH4+. Plants showed a limited capacity to take up D-trialanine (0.04±0.03 µmol g-1 root DW h-1), but did not appear to be able to metabolise it. We conclude that wheat is able to utilise L-peptide and D-amino acid N at rates comparable to those of N forms of acknowledged importance, namely L-amino acids and inorganic N. This is true even when solutes are supplied at realistic soil concentrations and when other forms of N are available. We suggest that it may be necessary to reconsider which forms of soil N are important in the terrestrial N cycle. © 2011 Hill et al.

    Original languageEnglish
    Article numbere19220
    JournalPLoS ONE
    Volume6
    Issue number4
    DOIs
    Publication statusPublished - Apr 2011

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    Hill, P. W., Quilliam, R. S., DeLuca, T. H., Farrar, J., Farrell, M., Roberts, P., Newsham, K. K., Hopkins, D. W., Bardgett, R. D., & Jones, D. L. (2011). Acquisition and assimilation of nitrogen as peptide-bound and D-enantiomers of amino acids by wheat. PLoS ONE, 6(4), [e19220]. https://doi.org/10.1371/journal.pone.0019220