Unlocking the genetic basis of monarch butterflies' use of medicinal plants

Abstract

A comparison between the two milkweed species revealed a total of five immune genes that were down-regulated in larvae reared on the high-cardenolide species (Figure 1). The authors acknowledged that this was not a large number of immune genes that were downregulated (four in gut tissue, one in the rest of the body). However, if the products of these immune genes are resource-expensive, then individuals with less investment in immunity can rely instead on sequestered cardenolides, which should be favoured by selection. From the data here, this selection would only have occurred when individuals were feeding on the high-cardenolide host plant because the down-regulation does not occur on the low-cardenolide host plant. This evidence also suggests that down-regulation is

The Effect of Phenoloxidase Activity on Survival Is Host Plant Dependent in Virus-Infected Caterpillars

“…Recent evidence from monarch caterpillars ( Danaus plexippus ) suggests that host plant chemistry can play a critical role in surviving an infection of the protozoan parasite Ophryocystis elektroscirrha (OE). Monarch caterpillars reared on host plant species with high cardenolide concentrations downregulated a handful of immune genes, but were more likely to survive an infection, suggesting a key role of plant chemistry in protection and mediation of the host–pathogen interaction ( Smilanich and Nuss 2019 , Tan et al 2019 ). Thus, the role of the immune system in protection against pathogens may be heavily influenced by host plant identity.…”

Elevated atmospheric concentrations of CO2 increase endogenous immune function in a specialist herbivore

“…Subsequent studies that survey the transcriptomic responses of monarchs to infection under simulated future environmental conditions will improve our understanding of the environmental contingency of these parasitic behaviours. Additionally, these transcriptomic studies may shed light on the complex relationship between detoxification and immunity (Smilanich & Nuss, 2019) that may add further depth to the phytochemical contingency of herbivorous host immunity in a changing world.…”

“…Among the detoxification genes upregulated by the medicinal milkweed were a glutathione S‐transferase (DPOGS210488) and a carboxyl esterase (DPOGS204275). The downregulation of immune genes in response to feeding on a medicinal milkweed species regardless of infection status suggests that coevolution among monarchs, milkweed, and O. elektroscirrha has reduced monarch reliance on endogenous immunity, and perhaps, favoured cardenolides as an exogenous functional replacement for endogenous immune activity (Smilanich & Nuss, 2019).…”

Connecting plant species and natural products from the Canadian prairie ecological zone to biomedical knowledge

“…There are several examples of co-evolution between diverse organisms in the prairie ecological zone that are astonishing in their specificity and reside under a theme of connectivity in biology. The monarch butterfly (Danaus plexippus) feeds on the toxic prairie plant, milkweed (Asclepias incarnata L. (Apocynaceae)) which protects the butterfly against parasites, such as Ophryocystis elektroscirrha (Smilanich and Nuss, 2019). An example of a vertebrate (avian) and Asteraceae species relationship in the prairie setting is shown with the sage grouse (Centrocersus urophasianus) and the silver sagebrush (Artemisia cana Pursh.)…”