How do plants kill butterfly eggs?

When induced by microbes, HR functions to stop growth of biotrophic pathogens (that is pathogens that need living tissue to survive). When triggered by insect eggs, necrosis leads to desiccation and dropping off of the eggs, killing the eggs and thus protecting the plant to feeding by butterfly larvae (caterpillars). Pathogen-induced HR is known to lead to resistance not only to the causing pathogen, but also makes other parts of the plant more resistant to future infections (called systemic acquired resistance). Insect egg-induced HR makes plants also become more attractive to egg parasitoids that kill the eggs.

The resemblance of insect egg-induced HR and the defense response to pathogens in plants suggest a role of microbes on or below the eggs. Pieris eggs were also shown to lead to systemic acquired resistance in the model plant Arabidopsis, and the response in this species is accompanied by a similar defense response as to pathogens, including expression of defense genes, generation of reactive oxygen species (ROS) and callose deposition, but without a visible necrosis. The molecular mechanisms of egg-induced HR in Brassica nigra are not yet characterized. The aim of this project is to compare HR in B. nigra induced by Pieris eggs with that to microbes and understand if the mechanisms behind it are general defense responses, or are specific to the elicitor. Can oviposition by P. brassicae also enhance resistance to pathogens in B. nigra?

You will work with insect herbivores and pathogens on Brassica nigra. You will perform plant phenotyping, measure gene expression, perform ROS assays, perform pathogenicity assays and test mortality of insect eggs and caterpillars.