Fungal nutrient allocation in common mycorrhizal networks is regulated by the carbon source strength of individual host plants.
Common mycorrhizal networks (CMNs) of arbuscular mycorrhizal (AM) fungi in the soil simultaneously provide multiple host plants with nutrients, but the mechanisms by which the nutrient transport to individual host plants within one CMN is controlled are unknown. Using radioactive and stable isotopes, we followed the transport of phosphorus (P) and nitrogen (N) in the CMNs of two fungal species to plants that differed in their carbon (C) source strength, and correlated the transport to the expression of mycorrhiza-inducible plant P (MtPt4) and ammonium (1723.m00046) transporters in mycorrhizal roots. AM fungi discriminated between host plants that shared a CMN and preferentially allocated nutrients to high-quality (nonshaded) hosts. However, the fungus also supplied low-quality (shaded) hosts with nutrients and maintained a high colonization rate in these plants. Fungal P transport was correlated to the expression of MtPt4. The expression of the putative ammonium transporter 1723.m00046 was dependent on the fungal nutrient supply and was induced when the CMN had access to N. Biological market theory has emerged as a tool with which the strategic investment of competing partners in trading networks can be studied. Our work demonstrates how fungal partners are able to retain bargaining power, despite being obligately dependent on their hosts.
Biology and Microbiology Department, South Dakota State University, Brookings, SD, 57007, USA.
Carl R
CR
Fellbaum
Biology and Microbiology Department, South Dakota State University, Brookings, SD, 57007, USA.
Jerry A
JA
Mensah
Biology and Microbiology Department, South Dakota State University, Brookings, SD, 57007, USA.
Adam J
AJ
Cloos
USDA, Agriculture Research Service, Eastern Regional Research Center, Wyndmoor, PA, 19038-8598, USA.
Gary E
GE
Strahan
USDA, Agriculture Research Service, Eastern Regional Research Center, Wyndmoor, PA, 19038-8598, USA.
Philip E
PE
Pfeffer
Institute of Ecological Science, Vrije Universiteit, De Boelelaan 1085, 1081 HV, Amsterdam, the Netherlands.
E Toby
ET
Kiers
Biology and Microbiology Department, South Dakota State University, Brookings, SD, 57007, USA.
Heike
H
Bücking
D002244:Carbon / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D046913:Medicago truncatula / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D038821:Mycorrhizae / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism* / Q000382:microbiology*; D013559:Symbiosis
D027682:Cation Transport Proteins; D010710:Phosphates; D010940:Plant Proteins; C088952:ammonium transporters, plant; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
Medicago; arbuscular mycorrhizal (AM) symbiosis; cooperation; decision making; mutualism; nitrogen transport; phosphate transport; photosynthetic activity