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Applied and Environmental Microbiology, June 2006, p. 4115-4120, Vol. 72, No. 6
0099-2240/06/$08.00+0     doi:10.1128/AEM.02154-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Effect of P Availability on Temporal Dynamics of Carbon Allocation and Glomus intraradices High-Affinity P Transporter Gene Induction in Arbuscular Mycorrhiza

Pål Axel Olsson,* Maria C. Hansson, and Stephen H. Burleigh

Department of Ecology, Ecology Building, Lund University, SE-223 62 Lund, Sweden

Received 12 September 2005/ Accepted 22 March 2006

Arbuscular mycorrhizal (AM) fungi depend on a C supply from the plant host and simultaneously provide phosphorus to the colonized plant. We therefore evaluated the influence of external P on C allocation in monoxenic Daucus carota-Glomus intraradices cultures in an AM symbiosis. Fungal hyphae proliferated from a solid minimal medium containing colonized roots into a C-free liquid minimal medium with high or low P availability. Roots and hyphae were harvested periodically, and the flow of C from roots to fungus was measured by isotope labeling. We also measured induction of a G. intraradices high-affinity P transporter to estimate fungal P demand. The prevailing hypothesis is that high P availability reduces mycorrhizal fungal growth, but we found that C flow to the fungus was initially highest at the high P level. Only at later harvests, after 100 days of in vitro culture, were C flow and fungal growth limited at high P availability. Thus, AM fungi can benefit initially from P-enriched environments in terms of plant C allocation. As expected, the P transporter induction was significantly greater at low P availability and greatest in very young mycelia. We found no direct link between C flow to the fungus and the P transporter transcription level, which indicates that a good C supply is not essential for induction of the high-affinity P transporter. We describe a mechanism by which P regulates symbiotic C allocation, and we discuss how this mechanism may have evolved in a competitive environment.

* Corresponding author. Mailing address: Department of Ecology, Ecology Building, Lund University, SE 223 62 Lund, Sweden. Phone: 46-46-222-9614. Fax: 46-46-222-4158. E-mail: Pal_Axel.Olsson{at}ekol.lu.se.

Applied and Environmental Microbiology, June 2006, p. 4115-4120, Vol. 72, No. 6
0099-2240/06/$08.00+0     doi:10.1128/AEM.02154-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Olsson, P. A., Hammer, E. C., Wallander, H., Pallon, J. (2008). Phosphorus Availability Influences Elemental Uptake in the Mycorrhizal Fungus Glomus intraradices, as Revealed by Particle-Induced X-Ray Emission Analysis. Appl. Environ. Microbiol. 74: 4144-4148 [Abstract] [Full Text]  


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