Metabolization and sequestration of plant specialized metabolites in insect herbivores: Current and emerging approaches

Abstract

Herbivorous insects encounter diverse plant specialized metabolites (PSMs) in their diet, that have deterrent, anti-nutritional, or toxic properties. Understanding how they cope with PSMs is crucial to understand their biology, population dynamics, and evolution. This review summarizes current and emerging cutting-edge methods that can be used to characterize the metabolic fate of PSMs, from ingestion to excretion or sequestration. It further emphasizes a workflow that enables not only to study PSM metabolism at different scales, but also to tackle and validate the genetic and biochemical mechanisms involved in PSM resistance by herbivores. This review thus aims at facilitating research on PSM-mediated plant-herbivore interactions.

Characterisation and localisation of plant metabolites involved in pharmacophagy in the turnip sawfly

“…The washed bodies contained the substantial amounts of both compounds, highlighting that the compounds are incorporated into the body tissue. Nevertheless, findings of both focal compounds in surface washes support the idea that the adults distribute the two focal compounds via cleaning behaviour on their body or even may excrete them via potential glands as known for other species [ 34 ]. For example, adults of the pine sawfly, Diprion similis (Hymenoptera: Diprionidae), excrete pheromones from abdominal glands, followed by cleaning behavior and probably dispersion of these compounds over the body [ 35 ].…”

The detoxification role of P450 genes implicated in adaptation of Helicoverpa armigera to walnut phytochemistry

“…In addition to detoxi cation enzymes, digestive enzymes also play a role in the adaptation of herbivorous insects to novel plants by degrading toxic metabolites (Simon et al 2015;Jeckel et al 2022). In our study, feeding H. armigera larvae with any of the three walnut fruit treatments, at both time points, changed the expression levels of digestive enzymes (Fig.…”

“…In recent years, with rapid development of next-generation sequencing technology, an increasing number of studies have employed RNA-seq to explore adaptive changes in insects in response to different host plants or xenobiotic phytochemicals (Heiko et al 2014;Jeckel et al 2022). For example, transcriptomic analysis was used to determine the mechanism of adaptation for the maize pest Diabrotica virgifera to different host plants.…”

The Chemical Ecology of Benzoxazinoids

“…[27] Counteradaptations to plant defenses include resistance and tolerance strategies. [190] While tolerance refers to adaptations that prevents from damage (e.g. target insensitivity), resistance refers to the active transport and/ or biotransformation of the plant defensive compound.…”

“…target insensitivity), resistance refers to the active transport and/ or biotransformation of the plant defensive compound. [190] To date, resistance strategies to benzoxazinoids were mostly investigated and include the isomerization of (2R)DIMBOA-Glc to (2S)-DIMBOA-Glc by Spodoptera frugiperda, [191] MBOA N-glycosylation by S. frugiperda and Diabrotica virgifera, [4,192] and detoxification through cytochrome P450 and glutathione S-transferase. [188] The root herbivore, D. virgifera, further sequesters HDMBOA-Glc and MBOA-Glc in its hemolymph and uses them for its own protection from entomopathogenic nematodes.…”