Gut-specific cardenolide-resistant sodium pump primed an omnivore to feed on toxic oleander

Apocynaceae plants produce toxic cardenolides to defend against their herbivores. Cardenolides could inhibit the a subunit of Na+ forward slash K+-ATPase (ATP alpha), which plays critical roles in biological processes such as muscle contraction, neural function, and osmoregulation. Numerous herbivores that specialized on cardenolides-producing milkweeds carry parallel molecular changes in ATPa that confer resistance. We found that Pacific Ducetia (Ducetia japonica), an omnivorous katydid, could feed on cardenolides-rich oleander leaves. ATPa in D. japonica has under-gone parallel molecular changes just like milkweed specialists. These changes evolved at the common ancestors of the leaf katydids before the diversification of Apocynaceae and may prime species in this lineage to feed on cardenolides-rich food. In summary, we reported the first case of cardenolide resistance in katydid, with convergent molecular evolution in ATPa, also an unusual case of cardenolides resistance in nonspecialist species that evolved earlier than the currently known cardenolide-producing plants.

Automated summary

Apocynaceae plants produce toxic cardenolides that can be utilized and confer resistance by herbivores. Omnivorous katydid Pacific Ducetia can feed on cardenolides-rich oleander leaves, showing an unusual case of cardenolide resistance in nonspecialist species.