Chemical Ecology of Plant-herbivore Interactions

Plants produce a puzzling diversity of defensive chemicals in their struggle to deter herbivorous enemies. Complex chemical mixtures may present defensive advantages over single compounds, for example via multi-target toxicity or compound-compound facilitation. Chemical diversification is therefore considered a strategy to escape coevolved herbivores. At the same time, such diversification must be costly to the plant, in terms of both raw building blocks and maintenance costs for increasingly complex synthesizing machinery.

We aim to elucidate the selective forces that drive chemical diversification. We use a newly established model plant system and employ a combination of experimental ecology and different techniques including metabolomics, transcriptomics, and phylogenetic comparisons. In a two-pronged approach, we focus on the defensive benefits of diverse chemical mixtures via altered feeding behavior and success of generalist and specialist herbivores, as well as on the cost of diversification in terms of negative impact on plant growth and reproduction. Ultimately, we will thus be able to link variation in genes and metabolites to success in a variable and changing environment.

• Herbivore-induced plant volatiles mediate defense regulation in maize leaves but not in maize roots
  van Doan, Cong; Zust, Tobias; Maurer, Corina; Zhang, Xi; Machado, Ricardo A. R.; et al.
  Plant Cell And Environment 10.1111/pce.14052  Early Access: APR 2021
• The plant metabolome guides fitness-relevant foraging decisions of a specialist herbivore
  Machado, Ricardo A. R.; Theepan, Vanitha; Robert, Christelle A. M.; Zust, Tobias; Hu, Lingfei; Su, Qi; Schimmel, Bernardus C. J.; Erb, Matthias
  PLOS BIOLOGY 19(2) Article Number: e3001114, DOI: 10.1371/journal.pbio.3001114   FEB 2021
• Less Is More: a Mutation in the Chemical Defense Pathway of Erysimum cheiranthoides (Brassicaceae) Reduces Total Cardenolide Abundance but Increases Resistance to Insect Herbivores
  Mirzaei, Mahdieh; Zuest, Tobias; Younkin, Gordon C.; Hastings, Amy P.; Alani, Martin L.; Agrawal, Anurag A; Jander, G
  Journal Of Chemical Ecology 10.1007/s10886-020-01225-y DEC 2020
• Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae)
  Zuest, Tobias; Strickler, Susan R.; Powell, Adrian F.; Mabry, Makenzie E.; An, Hong; et al.
  Elife  DOI: 10.7554/eLife.51712  APR 7 2020
• Heritable variation in root secondary metabolites is associated with recent climate
  Bont, Zoe; Zust, Tobias; Arce, Carla C. M.; Huber, Meret; Erb, Matthias
  Journal Of Ecology,  DOI: 10.1111/1365-2745.13441  JUN 2020
• Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae)
  ELIFE 9, DOI: 10.7554/eLife.51712 Published: APR 7 2020
  Zuest, Tobias; Strickler, Susan R; Powell, Adrian F., et al.
• Toxicity of Milkweed Leaves and Latex: Chromatographic Quantification Versus Biological Activity of Cardenolides in 16 Asclepias Species
  Zuest, Tobias; Petschenka, Georg; Hastings, Amy P.; Agrawal, Anurag A.
  JOURNAL OF CHEMICAL ECOLOGY, 45 (1):50-60; 10.1007/s10886-018-1040-3 JAN 2019
• Convergent evolution of a metabolic switch between aphid and caterpillar resistance in cereals
  Li, B; Forster, C; Robert, CAM; Zust, T; Hu, L; Machado, RAR; Berset, JD; Handrick, V; Knauer, T; Hensel, G; Chen, W; Kumlehn, J; Yang, P; Keller, B; Gershenzon, J; Jander, G; Kollner, TG; Erb, M
  SCIENCE ADVANCES, 4 (12):10.1126/sciadv.aat6797 DEC 2018
• Erysimum cheiranthoides, an ecological research system with potential as a genetic and genomic model for studying cardiac glycoside biosynthesis
  Zust, T; Mirzaei, M; Jander, G
  PHYTOCHEMISTRY REVIEWS 17(6): 1239-1251, DOI: 10.1007/s11101-018-9562-4, DEC 2018
• Climate Change and Insect Pests: Resistance Is Not Futile?
  SN Johnson, T Züst
  Trends in plant science 23 (5), 367-369, 2018
• What doesn't kill you makes you stronger: the burdens and benefits of toxin sequestration in a milkweed aphid
  T Züst, S Mou, AA Agrawal
  Functional Ecology 10.1111/1365-2435.1314 2018
• Erysimum cheiranthoides, an ecological research system with potential as a genetic and genomic model for studying cardiac glycoside biosynthesis
  T Züst, M Mirzaei, G Jander
  Phytochemistry reviews, 1-13, https://doi.org/10.1007/s11101-018-9562-4 2018
• Population transcriptomic characterization of the genetic and expression variation of a candidate progenitor of Miscanthus energy crops 
  Juan Yan, Zhihong Song, Qin Xu, Lifang Kang, Caiyun Zhu, Shilai Xing, Wei Liu, Josef Greimler, Tobias Züst, Jianqiang Li, Tao Sang
  MOLECULAR ECOLOGY, 26 (21): 5911-5922; https://doi.org/10.1111/mec.14338 NOV 2017
• Trade-offs between plant growth and defense against insect herbivory: an emerging mechanistic synthesis
  T Züst, AA Agrawal
  Annual Review of Plant Biology 68, 513-534, https://doi.org/10.1146/annurev-arplant-042916-040856 2017
• Plant chemical defense indirectly mediates aphid performance via interactions with tending ants 
  Zuest, Tobias; Agrawal, Anurag A. 
  ECOLOGY, 98 (3): 601-607; https://doi.org/10.1002/ecy.1707 MAR 2017
• …

• Evolution of cardiac glycosides in Erysimum spp.
• Molecular mechanisms of phytochemical diversification
• Inducible defenses and growth costs
• Herbivore tolerance to basal and novel defenses
• Sequestration of plant toxins and higher-trophic interactions

• Natural variation in the resistance of dandelion (Taraxacum officinale) to aphids
• Physiological mechanisms of toxicity
• Community ecology