title: Forms of nitrogen uptake, translocation, and transfer via arbuscular mycorrhizal fungi: a review.
abstract: Arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the roots of more than 80% of land plants. Experiments on the relationship between the host plant and AM in soil or in sterile root-organ culture have provided clear evidence that the extraradical mycelia of AM fungi uptake various forms of nitrogen (N) and transport the assimilated N to the roots of the host plant. However, the uptake mechanisms of various forms of N and its translocation and transfer from the fungus to the host are virtually unknown. Therefore, there is a dearth of integrated models describing the movement of N through the AM fungal hyphae. Recent studies examined Ri T-DNA-transformed carrot roots colonized with AM fungi in (15)N tracer experiments. In these experiments, the activities of key enzymes were determined, and expressions of genes related to N assimilation and translocation pathways were quantified. This review summarizes and discusses the results of recent research on the forms of N uptake, transport, degradation, and transfer to the roots of the host plant and the underlying mechanisms, as well as research on the forms of N and carbon used by germinating spores and their effects on amino acid metabolism. Finally, a pathway model summarizing the entire mechanism of N metabolism in AM fungi is outlined.
authors: College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004, China. hrjin@zjnu.cn
authors: Hairu
authors: H
authors: Jin
authors: Jie
authors: J
authors: Liu
authors: Jing
authors: J
authors: Liu
authors: Xiaowei
authors: X
authors: Huang
mesh_terms: D001120:Arginine / Q000378:metabolism; D001692:Biological Transport; D054884:Host-Pathogen Interactions; D008954:Models, Biological; D025282:Mycelium / Q000378:metabolism* / Q000502:physiology; D038821:Mycorrhizae / Q000378:metabolism* / Q000502:physiology; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013559:Symbiosis
chemical_list: D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D001120:Arginine; D009584:Nitrogen