Abstract
The long held but challenged view that plants do not synthesize sialic acids was re-evaluated using two different procedures to isolate putative sialic acid containing material from plant tissues and cells. The extracts were reacted with 1,2-diamino-4,5-methylene dioxybenzene and the fluorescently labelled 2-keto sugar acids analysed by reversed phase and normal phase HPLC and by HPLC–electrospray tandem mass spectrometry. No N-glycolylneuraminic acid was found in the protein fraction from Arabidopsis thaliana MM2d cells. However, we did detect 3-deoxy-d-manno-octulosonic acid and trace amounts (3–18 pmol/g fresh weight) of a compound indistinguishable from N-acetylneuraminic acid by its retention time and its mass spectral fragmentation pattern. Thus, plant cells and tissues contain five orders of magnitude less sialic acid than mammalian tissues such as porcine liver. Similar or lower amounts of N-acetylneuraminic acid were detected in tobacco cells, mung bean sprouts, apple and banana. Yet even yeast and buffer blanks, when subjected to the same isolation procedures, apparently contained the equivalent of 5 pmol of sialic acid per gram of material. Thus, we conclude that it is not possible to demonstrate unequivocally that plants synthesize sialic acids because the amounts of these sugars detected in plant cells and tissues are so small that they may originate from extraneous contaminants.
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Abbreviations
- DMB:
-
1,2-Diamino-4,5-methylene dioxybenzene
- KDO:
-
3-Deoxy-d-manno-octulosonic acid
- LC:
-
Liquid chromatography
- MS:
-
Mass spectrometry
- Neu5Ac:
-
N-Acetylneuraminic acid
- Neu5Gc:
-
N-Glycolylneuraminic acid
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Acknowledgments
This work was supported by grant LS 154 from the Vienna Science and Technology Fund (WWTF). We thank Ing. Thomas Dalik (Department of Chemistry, BOKU, Vienna) for performing the amino acid analyses. We cordially thank Don Jarvis (University of Wyoming, Laramie, WY, USA) for language editing the manuscript. We thank Bayer CropScience for the gift of MM2d cells, Gerhard Adam (Department of Plant Biotechnology, BOKU, Vienna) for the gift of tobacco NT1 cells and Jennifer Schoberer for help with cultivation of the cells.
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Zeleny, R., Kolarich, D., Strasser, R. et al. Sialic acid concentrations in plants are in the range of inadvertent contamination. Planta 224, 222–227 (2006). https://doi.org/10.1007/s00425-005-0206-8
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DOI: https://doi.org/10.1007/s00425-005-0206-8