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Updated: Aug 25, 2026

Production of Arbuscular Mycorrhizal (AM) Fungal Inoculum and Phenotypic Evaluation of Rice and AM Symbiosis Under Saline Conditions
Published on: March 14, 2025
Different nitrogen sources modulate activity but not expression of glutamine synthetase in arbuscular mycorrhizal
Magdalene Breuninger1, Carmen G Trujillo, Esther Serrano
1Physiological Ecology of Plants Department, University of Tübingen, Auf der Morgenstelle 1, Tübingen 72076, Germany.
Abstract:
Glutamine synthetase (GS) is a central enzyme of nitrogen metabolism that allows assimilation of nitrogen and biosynthesis of glutamine. We isolated the cDNA encoding GS from two arbuscular mycorrhizal fungi, Glomus mosseae (GmGln1) and Glomus intraradices (GiGln1). The deduced protein orthologues have a high degree of similarity (92%) with each other as well as with GSs from other fungi. GmGln1 was constitutively expressed during all stages of the fungal life cycle, i.e., spore germination, intraradical and extraradical mycelium. Feeding experiments with different nitrogen sources did not induce any change in the mRNA level of both genes independent of the symbiotic status of the fungus. However, GS activity of extraradical hypahe in G. intraradices was considerably modulated in response to different nitrogen sources. Thus, in a N re-supplementation time-course experiment, GS activity responded quickly to addition of nitrate, ammonium or glutamine. Re-feeding with ammonium produced a general increase in GS activity when compared with hyphae grown in nitrate as a sole N source.
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