Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae).

eLife 2020 Apr 07

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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 novel cardenolides as defenses. Here we test macroevolutionary hypotheses on co-expression, co-regulation, and diversification of these potentially redundant defenses across this genus. We sequenced and assembled the genome of E. cheiranthoides and foliar transcriptomes of 47 additional Erysimum species to construct a phylogeny from 9868 orthologous genes, revealing several geographic clades but also high levels of gene discordance. Concentrations, inducibility, and diversity of the two defenses varied independently among species, with no evidence for trade-offs. Closely related, geographically co-occurring species shared similar cardenolide traits, but not glucosinolate traits, likely as a result of specific selective pressures acting on each defense. Ancestral and novel chemical defenses in Erysimum thus appear to provide complementary rather than redundant functions. © 2020, Züst et al.

Citation

Tobias Züst, Susan R Strickler, Adrian F Powell, Makenzie E Mabry, Hong An, Mahdieh Mirzaei, Thomas York, Cynthia K Holland, Pavan Kumar, Matthias Erb, Georg Petschenka, José-María Gómez, Francisco Perfectti, Caroline Müller, J Chris Pires, Lukas A Mueller, Georg Jander. Independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae). eLife. 2020 Apr 07;9