An antagonist treatment in combination with tracer experiments revealed isocitrate pathway dominant to oxalate biosynthesis in Rumex obtusifolius L.
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Oxalate accumulates in leaves of certain plants such as Rumex species (Polygonaceae). Oxalate plays important roles in defense to predator, detoxification of metallic ions, and in hydrogen peroxide formation upon wounding/senescence. However, biosynthetic pathways of soluble oxalate are largely unknown. In the present study we analysed Rumex obtusifolius L. treated with itaconate (an antagonist to isocitrate). Comprehensive metabolome analysis using capillary electrophoresis-mass spectrometry showed that oxalate content of “new leaves” was notably down-regulated by itaconate, as opposed to the accumulation of citrate. The 13CO2 feeding experiment revealed that oxalate accumulation in new leaves was affected by citrate translocation from stems. The results suggested that excess oxalate in new leaves of R. obtusifolius was synthesized primarily via the isocitrate pathway utilizing citrate delivered from stems.
KeywordsRumex obtusifolius L. Capillary electrophoresis–mass spectrometry Oxalate Citrate Itaconate Isocitrate lyase
This research was supported by a grant from the Program for Promotion of Basic and Applied Researches for Innovations in Bio-oriented Industry (BRAIN), Japan, and a grand from MEXT, Japan. We thank Dr. Ko Noguchi (The University of Tokyo), Dr. Masatoshi Yamaguchi (Saitama University) and Dr. Kentaro Takahara (The University of Tokyo) for helpful advice.
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