Glycine metabolism by plant roots and its occurrence in Australian plant communities

• Published in: Functional Plant Biology
• Main Authors: Schmidt, S., Stewart, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cwlth Scientific and Industrial Res. Organization 1999
• Subjects: Plant Sciences; Amino Acids; Aminotransferase; Glycine Metabolism; Enzyme Inhibitors; Cluster Roots; Organic N; Soil N Sources; N-15-labelling; Serine Hydroxymethyltransferase; Antarctic Macquarie Island; N-15 Natural-abundance; Mycorrhizal Associations; Pisum-sativum; Amino-acids; Organic Nitrogen; Vascular Plants; Soil Properties; Arctic Plants; Serine; 270402 Plant Physiology; C1; 780105 Biological sciences; Arctic; Antarctic; Antarc*; Macquarie Island
• Online Access: https://espace.library.uq.edu.au/view/UQ:35578

Soluble organic nitrogen, including protein and amino acids, was found to be a ubiquitous form of soil N in diverse Australian environments. Fine roots of species representative of these environments were found to be active in the metabolism of glycine. The ability to incorporate [N-15]glycine was widespread among plant species from subantarctic to tropical communities. In species from subantarctic herbfield, subtropical coral cay, subtropical rainforest and wet heathland, [N-15]glycine incorporation ranged from 26 to 45% of (NH4+)-N-15 incorporation and was 2- to 3-fold greater than (NO3-)-N-15 incorporation. Most semiarid mulga and tropical savanna woodland species incorporated [N-15]glycine and (NO3-)-N-15 in similar amounts, 18-26% of (NH4+)-N-15 incorporation. We conclude that the potential to utilise amino acids as N sources is of widespread occurrence in plant communities and is not restricted to those from low temperature regimes or where N mineralisation is limited. Seedlings of Hakea (Proteaceae) were shown to metabolise glycine, with a rapid transfer of N-15 from glycine to serine and other amino compounds. The ability to take up and metabolise glycine was unaffected by the presence of equimolar concentrations of NO3- and NH4+. Isonicotinic acid hydrazide (INH) did not inhibit the transfer of N-15-label from glycine to serine indicating that serine hydroxymethyltransferase was not active in glycine catabolism. In contrast aminooxyacetate (AOA) strongly inhibited transfer of N-15 from glycine to serine and labelling of other amino compounds, suggesting that glycine is metabolised in roots and cluster roots of Hakea via an aminotransferase.