RESEARCH ARTICLE Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae) Tobias Zu¨ st1*, Susan R Strickler2, Adrian F Powell2, Makenzie E Mabry3, Hong An3, Mahdieh Mirzaei2, Thomas York2, Cynthia K Holland2†, Pavan Kumar2‡, Matthias Erb1, Georg Petschenka4, Jose´ -Marı´aGo´ mez5, Francisco Perfectti6, Caroline Mu¨ ller7, J Chris Pires3, Lukas A Mueller2, Georg Jander2 1Institute of Plant Sciences, University of Bern, Bern, Switzerland; 2Boyce Thompson Institute, Ithaca, United States; 3Division of Biological Sciences, University of Missouri, Columbia, United States; 4Institut fu¨ r Insektenbiotechnologie, Justus- Liebig-Universita¨ t Giessen, Giessen, Germany; 5Department of Functional and Evolutionary Ecology, Estacio´n Experimental de Zonas A´ ridas (EEZA-CSIC), Almerı´a, Spain; 6Research Unit Modeling Nature, Department of Genetics, University of Granada, Granada, Spain; 7Department of Chemical Ecology, Bielefeld University, Bielefeld, Germany Abstract Phytochemical diversity is thought to result from coevolutionary cycles as specialization in herbivores imposes diversifying selection on plant chemical defenses. Plants in the speciose genus Erysimum (Brassicaceae) produce both ancestral glucosinolates and evolutionarily *For correspondence: novel cardenolides as defenses. Here we test macroevolutionary hypotheses on co-expression, co-
[email protected] regulation, and diversification of these potentially redundant defenses across this genus. We Present address: †Thompson sequenced and assembled the genome of E. cheiranthoides and foliar transcriptomes of 47 Biology Lab, Williams College, additional Erysimum species to construct a phylogeny from 9868 orthologous genes, revealing Williamstown, United States; several geographic clades but also high levels of gene discordance. Concentrations, inducibility, ‡Corteva Agriscience, Des and diversity of the two defenses varied independently among species, with no evidence for trade- Moines, United States | downloaded: 5.10.2021 offs.