Insect Herbivory Simulation and Insect Bioassays to Study Plant Stress Memory Response

Plant stress memory response is an emerging field in plant-insect interaction. Recent reports indicate phytohormone jasmonic acid (JA) triggers long-term effects on the defense phenotype, transcriptome, and DNA methylome of Arabidopsis. Long-term JA-mediated induced resistance required MYC2/3/4 transcription factors and epigenetic regulatory components that prepare plants for future insect herbivore threats. Three weeks after transient JA signaling, 5-week-old plants retained induced resistance against herbivory but showed increased susceptibility to pathogens. This mechanism is linked with long-term priming and/or upregulation of JA-dependent defense genes but repression of ethylene- and salicylic acid-dependent genes. Still more research is required to fully understand plant stress memory response in plant-insect interaction. Here, a detailed and reproducible protocol for simulated herbivory and sample collection for transcriptomic and metabolomic studies is described to investigate involved defense signaling pathways. Furthermore, the insect bioassay protocol is described to study insect performance on various plant genotypes. Both protocols are robust and could be useful to study plant stress memory response in plant defense mechanisms through simulated herbivory and direct insect performance and feeding behavior by insect bioassays.