ARS | Publication request: The Form of Nitrogen Stored and Transported to the RI T-Dna Carrot Root by the Extradical Hyphae of Am Fungi

Submitted to: Meeting Abstract
Publication Acceptance Date: August 2, 2004
Publication Date: August 24, 2004
Citation: Jin, H., Pfeffer, P.E., Shachar-Hill, Y., Douds, D.D., Piotrowski, E.G., Lammers, P.J. 2004. The Form Of Nitrogen Stored And Transported To The RI T-Dna Carrot Root By The Extradical Hyphae Of Am Fungi. Meeting Abstract #581.

Technical Abstract: We studied the form of nitrogen stored and transported by the fungal partner in the arbuscular mycorrhizal (AM) symbosis. The AM fungus Glomus intraradices was cultured in association with transformed roots of Daucus carota L. in petri dishes with two compartments. [15N]-NH4Cl, [guanido-15N]arginine, [15N413C6]arginine were added to the fungal compartment. Free amino acids of the extraradical mycelium and mycorrhizal root compartment tissue were analyzed with GC-MS after 1,3 or 6 wks of exposure. After exposure to [15N]-NH4 the main free amino acid in the extraradical mycelium was arginine, which had 99% enrichment in 15N. The concentration of arginine was about 200 nmol g-1 d.wt of hypha, and represented more than 90% of the total nitrogen in free amino acids. [guanido-15N] or [15N413C6] labeled arginine added to the fungal compartment, was observed intact in the free amino acids of the colonized root tissue. This indicated that arginine can be taken up directly by extraradical hyphae and transported to the colonized roots. Thus arginine is one form of nitrogen stored and transported to the root host by the extraradical hypha of AM fungi. Moreover, the arginine transported to the mycorrhizal compartment was broken down into ornithine and urea, consistent with our previous hypothesis that the urea cycle might be active in nitrogen transport in the AM symbiosis.