title: The interplay between P uptake pathways in mycorrhizal peas: a combined physiological and gene-silencing approach.
abstract: Arbuscular mycorrhizal fungi (AMF) have a key role in plant phosphate (Pi) uptake by their efficient capture of soil phosphorus (P) that is transferred to the plant via Pi transporters in the root cortical cells. The activity of this mycorrhizal Pi uptake pathway is often associated with downregulation of Pi transporter genes in the direct Pi uptake pathway. As the total Pi taken up by the plant is determined by the combined activity of mycorrhizal and direct pathways, it is important to understand the interplay between these, in particular the actual activity of the pathways. To study this interplay we modulated the delivery of Pi via the mycorrhizal pathway in Pisum sativum by two means: (1) Partial downregulation by virus-induced gene silencing of PsPT4, a putative Pi transporter gene in the mycorrhizal pathway. This resulted in decreased fungal development in roots and soil and led to reduced plant Pi uptake. (2) Changing the percentage of AMF-colonized root length by using non-, half-mycorrhizal or full-mycorrhizal split-root systems. The combination of split roots, use of ³²P and ³³P isotopes and partial silencing of PsPT4 enabled us to show that the expression of PsPT1, a putative Pi transporter gene in the direct pathway, was negatively correlated with increasing mycorrhizal uptake capacity of the plant, both locally and systemically. However, transcript changes in PsPT1 were not translated into corresponding, systemic changes in actual direct Pi uptake. Our results suggest that AMF have a limited long-distance impact on the direct pathway.
authors: Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
authors: Mette
authors: M
authors: Grønlund
authors: Merete
authors: M
authors: Albrechtsen
authors: I Elisabeth
authors: IE
authors: Johansen
authors: Edith C
authors: EC
authors: Hammer
authors: Tom H
authors: TH
authors: Nielsen
authors: Iver
authors: I
authors: Jakobsen
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport / Q000502:physiology; D020868:Gene Silencing; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D038821:Mycorrhizae / Q000502:physiology; D018532:Pisum sativum / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D028061:Phosphate Transport Proteins / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D012987:Soil / Q000737:chemistry; D013559:Symbiosis / Q000235:genetics / Q000502:physiology
chemical_list: D028061:Phosphate Transport Proteins; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D010940:Plant Proteins; D012987:Soil; D010758:Phosphorus