Poster

Jonathan Henson ^1,2, Malathy Palayam ³, Todd Naumann ¹, Nicholas Rhoades ^1,2, Susan McCormick ¹, Martha Vaughan ¹, Nitzan Shabek ³, and Guixia Hao ¹
1. Mycotoxin Prevention and Applied Microbiology Research Unit, NCAUR, USDA-ARS, Peoria, IL, 61604
2. Oak Ridge Institute for Science and Education. N. University St., Peoria, IL 61604
3. Department of Plant Biology, College of Biological Sciences, University of California - Davis, Davis, CA 95616
Corresponding Author: Guixia Hao; guixia.hao@usda.gov

Henson, Jonathan

jonathan.henson@usda.gov

Fusarium graminearum causes Fusarium head blight (FHB) in wheat and barley and produces trichothecene mycotoxins, including deoxynivalenol (DON) and its acetylated derivatives 3‑acetyldeoxynivalenol (3‑ADON) and 15‑acetyldeoxynivalenol (15‑ADON). Although DON is the most common toxin detected in contaminated grain, F. graminearum strains commonly produce either 3‑ADON or 15‑ADON in liquid culture. In this study, we demonstrated that Arabidopsis seedlings and wheat florets can convert 3‑ADON or 15‑ADON to DON. Through biochemical analyses, we identified Arabidopsis carboxylesterases (AtCXEs) capable of deacetylating 3-ADON, including AtCXE20, which exhibited substantial activity. Gene expression analysis further revealed that multiple AtCXEs are induced by 3‑ADON exposure, suggesting that additional AtCXEs may be involved in acetylated-DON conversion. Comparative genomic analysis identified wheat CXE (TaCXE) orthologs corresponding to Arabidopsis and Brachypodium distachyon CXEs. Among these, TaCXE15 was shown to deacetylate 3-ADON in a yeast expression system. Building on our previously determined crystal structures of AtCXE15 and AtCXE20, we are integrating structural modeling, molecular docking, and biochemical analyses to investigate the molecular determinants of 3-ADON recognition and hydrolysis. Additional structural studies, including co-crystallization and crystal soaking experiments, are being pursued to identify residues critical for substrate recognition and catalysis. High-priority wheat TaCXE candidates will subsequently be targeted using prime‑editing in wheat. Together, these studies aim to define the molecular mechanisms underlying CXE-mediated conversion of acetylated DON derivatives and evaluate whether specific wheat CXEs function as host susceptibility factors that could be targeted to reduce DON accumulation and FHB severity. This material is based upon work supported by the U.S. Department of Agriculture. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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