Margot Schulz1*, Sandra Kant1, Tom Colby2,3, Anne Harzen2, Jürgen Schmidt2, Dieter Sicker4 and Parisa Pourmoayyed1
1 IMBIO Institut für Biotechnologie der Pflanzen, Universität Bonn, Karlrobert Kreiten Str. 13, 53115 Bonn, Germany
2 Max-Planck-Institut für Züchtungsforschung, Carl von Linné Weg 10, 50829 Köln, Germany.
4 Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
3 present address: Max Planck Institute for Biology of Aging, Joseph-Stelzmann Str. 9b, 50931 Köln, Germany.
* Correspondence to: Margot Schulz. Email:
Purification of the benzoxazolinone (BOA)-glucosylating activity from maize roots by chromatographic methods and LC/MS/MS peptide analysis after 2d electrophoresis identified glucosyltransferase BX9 as the enzyme responsible for BOA-6-O-glucosylation. Immunoprecipitation and experiments with transgenic Arabidopsis thaliana lines corroborate the function of BX9 in detoxification of the intermediate BOA-6-OH. The BOA-6-O-glucosylation pathway is a “ready to go “mechanism, important to detoxify benzoxazolinone (BOA), before the detoxification pathway leading to glucoside carbamate synthesis is stablished. Oxidative modifications of BX9 after exposure to BOA seem to trigger the enzyme for acceptance of BOA-6-OH as a substrate. Consequently, reducing sulphur compounds inactivated BOA-6-OH glucosylation. BX9 has a higher affinity to BOA-6-OH than to DIMBOA when assayed at pH 8.0. For the substrate BOA-6-OH, Km-values were determined to be 120.7 μM, the Km value for UDPG were 360μM. The intermediate BOA-6-OH is a linker between BOA and MBOA detoxification, when MBOA is demethylated. Glucoside carbamate, a major BOA detoxification product later in the process, is a potent inhibitor of BOA-6-O-glucosylation (Ki 84μM). BOA detoxification pathways are competitive to the formation of benzoxazolinone derived phenoxazinone, a highly toxic compound for many organisms including plants. Benzoxazolinone detoxification is therefore of great importance for the survival of plant seedlings.
Keywords: Allelopathy, benzoxazolinone detoxification, BOA-6-O-glucoside, glucosyltransferase BX9, Zea mays
RECEIVED: November 18, 2015
ACCEPTED December 16, 2015