Suillus bovinus glutamine synthetase gene organization, transcription and enzyme activities in the Scots pine mycorrhizosphere developed on forest humus

• Published in: The New phytologist Vol. 164; no. 2; pp. 389 - 399
• Main Authors: Juuti, Jarmo T., Jokela, Sanna, Paulin, Lars, Timonen, Sari, Sen, Robin
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science 01.11.2004; Blackwell Science Ltd; Blackwell
• Subjects: amino acid sequences; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Complementary DNA; DNA; DNA libraries; ectomycorrhiza; enzyme activity; Enzymes; extramatrical mycelium; forest soils; forest trees; Fundamental and applied biological sciences. Psychology; fungal proteins; Gels; glutamate-ammonia ligase; glutamine synthetase (GS); Introns; Messenger RNA; molecular sequence data; Mycelium; mycorrhizal fungi; mycorrhizosphere; nitrogen uptake; nucleotide sequences; Parasitism and symbiosis; phylogeny; Pine trees; Pinus sylvestris; Plant physiology and development; Plants and fungi; Quaternary ammonium compounds; RNA; sequence analysis; soil organic matter; Suillus bovinus; Symbiosis; transcription; transcription (genetics); transcription initiation site; transcription initiation sites; extramatrical mycelium; transcription; Basidiomycetes; Pinus sylvestris; Fungi; glutamine synthetase (GS); Enzymatic activity; Ligases; enzyme activity; Softwood forest tree; Gymnospermae; Ectomycorrhiza; Glutamate-ammonia ligase; transcription initiation site; Thallophyta; Symbiosis; Carbon-nitrogen ligases; Enzyme; Nitrogen; Metabolism; Gene expression; Symbiont; Nitrogen cycle; Mycorrhiza; nitrogen uptake; phylogeny; Coniferales; Spermatophyta; Mycelium; ectomycorrhiza
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2004.01166.x

• Glutamine synthetase (GS) expression and activity is of central importance for cellular ammonium assimilation and recycling. Thus, a full characterization of this enzyme at the molecular level is of critical importance for a better understanding of nitrogen (N) assimilation in the mycorrhizal symbiosis. • Genomic and cDNA libraries of Suillus bovinus were constructed to isolate the GS gene, glnA, and corresponding cDNAs. The transcription initiation site was identified and transcription and enzyme activities were characterized in pure culture mycelium and mycorrhiza, and extramatrical mycelium samples harvested from Scots pine-Suillus bovinus microcosms grown on forest humus. • Pure culture mycelium, mycorrhiza and extramatrical mycelium all exhibited equivalent levels of GS transcription, translation and enzyme activities. However, levels of transcription and enzyme activity did not correlate as a large majority of detectable transcripts showed specific 5′-end truncation. • Our data suggest that GS is constitutively expressed and not directly affected by environmental conditions of the symbiotic N uptake. Any changes in the intracellular ammonium level are most likely handled by regulatory flexibility of GS at enzyme level.