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PLANTS INTERACTING WITH OTHER ORGANISMS

Metabolic Profiles of Lolium perenne Are Differentially Affected by Nitrogen Supply, Carbohydrate Content, and Fungal Endophyte Infection^1,[W],[OA]

AgResearch, Palmerston North 4442, New Zealand (S.R., A.J.P., K.F., H.X.); and Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1 (J.A.N.)

Lolium perenne cultivars differing in their capacity to accumulate water soluble carbohydrates (WSCs) were infected with three strains of fungal Neotyphodium lolii endophytes or left uninfected. The endophyte strains differed in their alkaloid profiles. Plants were grown at two different levels of nitrogen (N) supply in a controlled environment. Metabolic profiles of blades were analyzed using a variety of analytical methods. A total of 66 response variables were subjected to a principle components analysis and factor rotation. The first three rotated factors (46% of the total variance) were subsequently analyzed by analysis of variance. At high N supply nitrogenous compounds, organic acids and lipids were increased; WSCs, chlorogenic acid (CGA), and fibers were decreased. The high-sugar cultivar ‘AberDove’ had reduced levels of nitrate, most minor amino acids, sulfur, and fibers compared to the control cultivar ‘Fennema’, whereas WSCs, CGA, and methionine were increased. In plants infected with endophytes, nitrate, several amino acids, and, magnesium were decreased; WSCs, lipids, some organic acids, and CGA were increased. Regrowth of blades was stimulated at high N, and there was a significant endophyte x cultivar interaction on regrowth. Mannitol, a fungal specific sugar alcohol, was significantly correlated with fungal biomass. Our findings suggest that effects of endophytes on metabolic profiles of L. perenne can be considerable, depending on host plant characteristics and nutrient supply, and we propose that a shift in carbon/N ratios and in secondary metabolite production as seen in our study is likely to have impacts on herbivore responses.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Susanne Rasmussen (susanne.rasmussen{at}agresearch.co.nz).

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.107.111898

^* Corresponding author; e-mail susanne.rasmussen{at}agresearch.co.nz.

Received October 28, 2007; accepted January 17, 2008; published January 24, 2008.