ARS | Publication request: Bidirectional Transfer of Carbon and Nitrogen Between Fungus and Host in the Arbuscular Mycorrhizal Symbiosis

Submitted to: Meeting Abstract
Publication Acceptance Date: May 10, 2004
Publication Date: August 16, 2004
Citation: Pfeffer, P.E., Douds, D.D., Schwartz, D.P., Govindarajulu, M., Bucking, W., Shachar-Hill, Y. 2004. Bidirectional Transfer Of Carbon And Nitrogen Between Fungus And Host In The Arbuscular Mycorrhizal Symbiosis. Meeting Abstract.

Technical Abstract: It is unclear whether the transfers of carbon (from plant to fungus) and nitrogen (from fungus to plant) in arbuscular mycorrhizas are unidirectional. We are using NMR, GC/MS and autoradiography to address this question by following the transfer of isotopically labeled metabolites in dual cultures of Ri T-DNA transformed carrot roots and Glomus intraradices. 13C1,3 glycerol and 13C2 acetate that can be taken up by the extraradical mycelium (ERM), were used to establish that carbon in the form of triglycerides moves back and forth between the ERM and the intraradical mycelium (IRM) but does not label host metabolites. Consequently, that carbon is not transferred to the host in nutritionally significant quantities. We also observed that carbon is moved from one root system to another via a common mycorrhizal network but that even when the recipient root system is carbon limited there is no significant transfer into host metabolic pools. This presentation will also report on the progress of autoradiographic experiments designed to localize transferred carbon within the recipient host root. 15N and 13C labeled substrates introduced to the ERM result in 15N labeled proteins in the mycorrhizal root indicating that amino acids are not transferred to the host. Little is known about the form of nitrogen transferred from the root to the ERM and whether it is obtained from the cortical cells or taken directly from the apoplast. Initial labeling experiments suggest that nitrogen is taken up by the fungus from the apoplast and not from intracellular host metabolic pools.