Plant Perception and Short-Term Responses to Phytophagous Insects and Mites

Abstract

Plant⁻pest relationships involve complex processes encompassing a network of molecules, signals, and regulators for overcoming defenses they develop against each other. Phytophagous arthropods identify plants mainly as a source of food. In turn, plants develop a variety of strategies to avoid damage and survive. The success of plant defenses depends on rapid and specific recognition of the phytophagous threat. Subsequently, plants trigger a cascade of short-term responses that eventually result in the production of a wide range of compounds with defense properties. This review deals with the main features involved in the interaction between plants and phytophagous insects and acari, focusing on early responses from the plant side. A general landscape of the diverse strategies employed by plants within the first hours after pest perception to block the capability of phytophagous insects to develop mechanisms of resistance is presented, with the potential of providing alternatives for pest control.

Keywords: acari; early signaling; effectors; elicitors; insect; phytophagous arthropods; plant defenses; plant receptors.

Figure 1

Early and late plant events in plant–phytophagous pest interactions. Insects and acari with different mouth structures and several feeding modes select host plants. Specific plant receptors (pattern recognition receptor, PRRs) recognize elicitors/effectors (damage-associated molecular patterns, DAMPs, and herbivore-associated molecular patterns, HAMPs) derived from either the plant or the phytophagous pest side (insects and acari) and activate downstream short-term and long-term defense responses. ROS, reactive oxygen species; RNS, reactive nitrogen species.

Figure 2

Elicitor (E)/effector (Eff) molecules from plant and phytophagous pest sides trigger, amplify, or suppress specific plant defense responses against pests. Phytophagous insect and acari species and orders are indicated.

Figure 3

Early plant events in plant–phytophagous pest interactions. Specific plant receptors (PRRs) recognize elicitors/effectors (HAMPs) derived from either the plant or the phytophagous pest side (insects and acari) that induce alterations in the membrane potential (Vm) and cytosolic Ca²⁺ influxes from the apoplast and organelles. Subsequently, Ca²⁺-sensing proteins are activated and reactive oxygen species (ROS) and reactive nitrogen species (RNS) burst is triggered. Then cytosolic Ca²⁺ concentration is restored via Ca²⁺-ATPases, and finally, in a second step, specific hormone-mediated defenses against pests are produced.