Relative Selectivity of Plant Cardenolides for Na+/K+-ATPases From the Monarch Butterfly and Non-resistant Insects
Petschenka G, Fei CS, Araya JJ and others. Frontiers in plant science, September 2018.
Read the paper Free to read · doi:10.3389/fpls.2018.01424
What this paper is about
Coevolutionary theory predicts a plant should aim its toxins at particular herbivores. The authors applied 17 different cardiac glycosides to the monarch's sodium-potassium pump and to the pumps of two insects that have no resistance.
The compounds were not equally potent across the three, so the structure of a cardenolide determines which animal it hurts most.
Summarised here from the abstract below. Not the authors’ words.
Abstract
A major prediction of coevolutionary theory is that plants may target particular herbivores with secondary compounds that are selectively defensive. The highly specialized monarch butterfly (Danaus plexippus) copes well with cardiac glycosides (inhibitors of animal Na+/K+-ATPases) from its milkweed host plants, but selective inhibition of its Na+/K+-ATPase by different compounds has not been previously tested. We applied 17 cardiac glycosides to the D. plexippus-Na+/K+-ATPase and to the more susceptible Na+/K+-ATPases of two non-adapted insects (Euploea core and Schistocerca gregaria). Structural features (e.g., sugar residues) predicted in vitro inhibitory activity and comparison of insect Na+/K+-ATPases revealed that the monarch has evolved a highly resistant enzyme overall. Nonetheless, we found evidence for relative selectivity of individual cardiac glycosides reaching from 4- to 94-fold differences of inhibition between non-adapted Na+/K+-ATPase and D. plexippus-Na+/K+-ATPase. This toxin receptor specificity suggests a mechanism how plants could target herbivores selectively and thus provides a strong basis for pairwise coevolutionary interactions between plants and herbivorous insects.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
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author = {{Milkweed USA}},
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