Plant perception of Herbivore- and Damage-Associated Molecular Patterns and its role in defense against insects

Abstract

Plants can interact with herbivores through complex signaling pathways involving the perception of herbivore-associated molecular patterns (HAMPs) and damage-associated molecular patterns (DAMPs) by pattern recognition receptors (PRRs). Upon recognition, the plant is able to induce an immunity response. Important early responses include calcium signaling, reactive oxygen species (ROS) production, and the activation of mitogen-activated protein kinase (MAPK) cascades. These signaling compounds are important for the induction of plant defense hormones/metabolites and expression of immunity genes, resulting in resistance against insect herbivores. This thesis investigates the mechanisms underlying plant defenses against herbivorous insects, focusing on the perception and response systems that activate these defenses. Several HAMP/DAMP – PRR pairs will be discussed, showing how perception of HAMP/DAMPs by their associated PRR can lead to induced immunity to herbivores. The thesis also explores the role of plant hormones, particularly jasmonic acid (JA) and salicylic acid (SA), in regulating defense mechanisms. JA is primarily involved in responses to chewing herbivores, while SA is associated with phloem-feeding insects. The interplay between these hormones and other signaling pathways, such as ethylene, adds a layer of complexity to the plant's defense strategies. Additionally, secondary metabolites, including terpenoids, flavonoids, and glucosinolates, are produced as part of the plant's defense, serving both as direct toxins to herbivores and as signals to attract natural enemies. Despite the advances in understanding plant-pathogen interactions, knowledge of plant responses to herbivory is less developed. Few PRR-HAMP and PRR-DAMP pairs have been characterized, indicating a gap in our comprehension of herbivore perception mechanisms. Further research is needed to understand these interactions on molecular level and improve plant resistance to herbivorous insects, ultimately contributing to enhanced agricultural practices and pest management strategies.