Molecular Interactions Between Plants and Insect Herbivores

Abstract

Diverse molecular processes regulate the interactions between plants and insect herbivores. Here, we review genes and proteins that are involved in plant–herbivore interactions and discuss how their discovery has structured the current standard model of plant–herbivore interactions. Plants perceive damage-associated and, possibly, herbivore-associated molecular patterns via receptors that activate early signaling components such as Ca2+, reactive oxygen species, and MAP kinases. Specific defense reprogramming proceeds via signaling networks that include phytohormones, secondary metabolites, and transcription factors. Local and systemic regulation of toxins, defense proteins, physical barriers, and tolerance traits protect plants against herbivores. Herbivores counteract plant defenses through biochemical defense deactivation, effector-mediated suppression of defense signaling, and chemically controlled behavioral changes. The molecular basis of plant–herbivore interactions is now well established for model systems. Expanding molecular approaches to unexplored dimensions of plant–insect interactions should be a future priority.

Foliar herbivory by caterpillars and aphids differentially affects phytohormonal signalling in roots and plant defence to a root herbivore

“…Responses of plants to D. radicum involve a strong activation of jasmonates. The JA pathway is well‐known for regulating defence against chewing herbivores, both in leaves and roots; in rice, mutants lacking a functional JA response were more susceptible to root herbivores (Erb & Reymond, ; Lu et al, ). Furthermore, both root herbivory and jasmonate treatment triggers maize roots to produce of a volatile compound that attracts entomopathogenic nematodes (Erb et al, ; Rasmann et al, ).…”

“…However, plants are by no means defenceless. When attacked by insects, plants respond in terms of gene expression, signal transduction via phytohormonal pathways, and eventually responses such as the biosynthesis of secondary metabolites (Erb & Reymond, ; Pieterse, Leon‐Reyes, Van der Ent, & Van Wees, ). In leaves, chewing herbivores commonly induce a defence response mediated by the jasmonic acid (JA) pathway, whereas phloem feeders usually induce the salicylic acid (SA) pathway (Pieterse, & Does D.V.d., Zamioudis C., Leon‐Reyes A., & Wees S.C.M.V., ).…”

Genes for ash tree resistance to an insect pest identified via comparative genomics

“…OG4469 is a probable orthologue of AtG-LecRK-1.6, a G-type lectin receptor kinase (LecRK) with ATP binding activity (Supplementary Note 4.3). G-type LecRKs can act as pattern recognition receptors (PRRs) in the perception of feeding insects 27 ; extracellular ATP is a damage-associated molecular pattern (DAMP) whose perception can trigger defence response related genes 27 . OG38407 appears orthologous to SNIPER4 ( Supplementary Fig.…”

“…with some having a role in plant defence 111,112 such as in response to the tobacco hawk moth (Manduca sexta) in Nicotiana attenuata 113 or to the brown planthopper (Nilaparvata lugens) in rice 114 . Extracellular ATP is associated with cell damage, and perception of ATP may play a role in defence response against insect herbivores via stimulation of the JA pathway 27 . AT5G24080 has also been named AtG-LecRK-I.6 by Teixeira et al 111 , who suggest it may be defective because its protein has an incomplete kinase domain and lacks some of the subdomains typically found in kinases.…”

“…AT4G27240 also encodes a zinc finger protein; both AT4G27240 and AT5G54630 are transcription factors 133 , but their functions are not fully characterised. AT5G54630 is expressed in response to brassinolide 134 , a brassinosteroid, which have a crucial role in regulating the growth-immunity trade-off 135 ; transcriptions factors act both up and downstream of phytohormone signalling to regulate defence responses 27 . One of the susceptible taxa included in our convergence analyses, F. ornus, may lack a functional copy of this gene ( Supplementary Table 6).…”