Most of the BXD excretion in the frass occurs in the form of glucosylated products. Our findings highlight the involvement of members of two major UGT families, UGT33 and UGT40, in the glycosylation of BXDs. Here, we identify UGTs involved in BXD detoxification by FAW larvae and examine how RNAi-mediated manipulation of the larval glucosylation capacity toward the major maize BXD, DIMBOA, affects larval growth. DIMBOA, the main BXD aglucone released by maize leaves, can be stereoselectively re-glucosylated by UDP-glycosyltransferases (UGTs) in the insect gut, rendering it non-toxic. BXDs stored as inert glucosides are converted into toxic aglucones by plant glucosidases upon herbivory. Spodoptera frugiperda, the fall armyworm (FAW), accepts a number of plants as hosts, and has particular success on plants of the Poaceae family such as maize, despite their benzoxazinoid (BXD) defenses. The relationship between plants and insects is continuously evolving, and many insects rely on biochemical strategies to mitigate the effects of toxic chemicals in their food plants, allowing them to feed on well-defended plants.

4Institute of Plant Sciences, University of Bern, Bern, Switzerland.

3Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS, United States.

2Department of Chemistry, Federal University of São Carlos, São Carlos, Brazil.

1Max Planck Institute for Chemical Ecology, Jena, Germany.

Heckel 1, Jonathan Gershenzon 1 and Daniel Giddings Vassão 1* Wouters 1,2, Katrin Luck 1, Elena Seibel 1, Seung-Joon Ahn 3, Christian Paetz 1, Maximilian Reinert 1, Heiko Vogel 1, Matthias Erb 4, David G.

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