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First published online December 23, 2004; 10.1104/pp.104.051839 Plant Physiology 137:190-198 (2005) © 2005 American Society of Plant Biologists Possible Roles for Mannitol and Mannitol Dehydrogenase in the Biotrophic Plant Pathogen Uromyces fabae1Phytopathologie, Fachbereich Biologie, Universität Konstanz, 78457 Konstanz, Germany (R.T.V., T.L., K.M.); Phytopathologie, Fachbereich Biologie, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany (M.H.); Biochemie der Pflanzen, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen, 37077 Gottingen, Germany (G.L.); and Phytopathologie, Wissenschaftszentrum Weihenstephan der Technischen Universität München, 85350 Freising-Weihenstephan, Germany (I.H.)
Levels of the C6-polyol mannitol were observed to rise dramatically in the biotrophic interaction of the rust fungus Uromyces fabae and its host plant Vicia faba. Mannitol was found in millimolar concentrations in extracts and apoplastic fluids of infected leaves and also in extracts of spores. We suggest that this polyol might have at least a dual function: first, as a carbohydrate storage compound, and second, as a scavenger of reactive oxygen species. Mannitol accumulation is accompanied by high expression of a mannitol dehydrogenase (MAD1) in haustoria. While MAD1 transcripts were detected in haustoria only, immunolocalization studies show that the gene product is also present in spores. Kinetic and thermodynamic analyses of the MAD1p catalyzed reactions indicate that the enzyme might be responsible for the production of mannitol in haustoria and for the utilization of mannitol in spores. Since V. faba is normally unable to synthesize or utilize polyols, the multipurpose usage of mannitol seems an ideal strategy for the fungal pathogen.
1 This work was supported by the Deutsche Forschungsgemeinschaft (grant no. Me 523/241 to K.M. and R.T.V.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.051839. * Corresponding author; e-mail ralf.voegele{at}uni-konstanz.de; fax 497531883035. Received August 18, 2004; returned for revision October 11, 2004; accepted October 18, 2004. This article has been cited by other articles:
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