Evolution of benzoxazinone biosynthesis

ALFONS GIERL
Lehrstuhl für Genetik
Technische Universität München
Am Hochanger 8
D-85350 Freising
Gierl@wzw.tum.de
http://www.wzw.tu-muenchen.de/genetik/

Benzoxazinones are a unique class of plant secondary metabolites abundant in Gramineae, including the major agricultural crops, maize, wheat and rye. Sporadically benzoxazinones are found in dicots, specifically in the families Acanthaceae, Ranunculaceae, Scrophulariaceae and Lamiaceae. For maize and wheat the pathway has been elucidated. However, no genes for the biosynthesis in dicots have been isolated. Hence, no data to discriminate between the two possibilities for the evolution of the pathway in monocots and dicots, - monophyletic origin or convergent evolution - are available. To address this question we investigated the benzoxazinoid producing plants Aphelandra squarrosa (Acanthaceae), Consolida orientalis (Ranunculaceae) and Lamium galeobdolon (Lamiaceae).

Indole is known to be the first pathway specific metabolite in Gramineae. Our results indicate that indole is also precursor for benzoxazinone biosynthesis of the three dicot plants. The candidate genes for this branchpoint reaction were isolated and characterized. Beside the biochemical determination of the function the genes we want to proof the involvement of the genes by knock down via RNAi.

Subsequent modifying reactions are analysed and the involved genes will be isolated. Preliminary results indicate that P450 enzymes are part of the benzoxazinone pathway in dicots.

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