Simulated Herbivory: The Key to Disentangling Plant Defence Responses

Abstract

Plants are subjected to a multitude of stimuli during insect herbivory, resulting in a complex and cumulative defence response. Breaking down the components of herbivory into specific stimuli and identifying the mechanisms of defence associated with them has thus far been challenging. Advances in our understanding of responses to inconspicuous stimuli, such as those induced by microbial symbionts in herbivore secretions and mechanical stimulation caused by insects, have shed light on the intricacies of herbivory. Here we provide a synthesis of the interacting impacts of herbivory on plants and the consequential complexities associated with uncoupling defence responses. We propose that simulated herbivory should be used to complement true herbivory in order decipher the mechanisms of insect herbivoreinduced plant defence responses.

How do herbivorous insects respond to drought stress in trees?

“…Plant defences may vary depending on the insects attacking them. Plants may recognise which herbivore is inflicting damage on them based on insect salivary constituents and the pattern of imposed damage, and induce defences accordingly (Bonaventure, 2018;Waterman et al, 2019). This hypothesis has been tested using agricultural pests, such as the Colorado potato beetle (Leptinotarsa decemlineata), the corn earworm (Helicoverpa zea), and the western corn rootworm (Diabrotica virgifera virgifera).…”

Combining Evolutionary Inference and Metabolomics to Identify Plants With Medicinal Potential

“…Many of these elicitors are produced by insects, and range from enzymes and modified lipids to sulfur containing fatty acids (Bonaventure et al, 2011). These elicitors have the ability to stimulate biosynthetic pathways within a plant (Waterman et al, 2019). Further, the action of these elicitors tends to be associated with certain plant-insect associations.…”

Microbes in Helicoverpa armigera oral secretions contribute to increased senescence around plant wounds

“…Plants come under attack from a wide range of natural enemies, some of the most significant being insect herbivores (consuming over 20% of annual net primary productivity) (Agrawal, 2011). In order to differentiate various stressors, plants have evolved the ability to initiate targeted defence responses against herbivores following recognition of specific chemical signals (Waterman et al, 2019). For example, many Lepidopteran larvae release oral secretions (OS) containing components from their gut and salivary glands during feeding (Peiffer & Felton, 2009).…”

“…Further, microbial associations formed with insects play a pivotal role in plant-herbivore interactions (Douglas, 1998;Pieterse & Dicke, 2007). For example, microbes derived from the insect gut are present in OS and can modify plant defences against herbivory; however, the extent of microbial involvement in plant-herbivore dynamics has not been fully explored (Waterman et al, 2019). Senescence around sites of infection or wounding is an important mechanism by which plants prevent the spread of biotrophic pathogens, as it establishes a physical barrier between infected and healthy cell types and can activate various defence pathways (Glazebrook, 2005;Iakimova & Woltering, 2018).…”

“…The extent of senescence is often used to determine the severity of biotrophic pathogen infection; however, senescence is seldom considered in experiments involving insect herbivory, even though such a response can be activated by insect-associated signal pathways (Devadas & Raina, 2002;Häffner et al, 2015). In order to better understand how plants defend themselves against insects, it is important to understand exactly which insect-associated stimuli plants are responding to (Waterman et al, 2019). Additionally, wound closure of areas damaged by insects can also inhibit herbivory through the production of feeding deterrents such as callose, lignin and other phenolic compounds, which simultaneously provide a barrier against microbes (Cui et al, 2013;Iakimova & Woltering, 2018).…”