Article

Le rôle des odeurs dans la communication entre les plantes et les insectes

The role of volatile organic compounds in plant-insect communication

¹ Sorbonne Université, Institut d’Écologie et des Sciences de l’Environnement de Paris, 4 place Jussieu, 75005 Paris, France
² Institut Universitaire de France, Paris, France

^* Auteur correspondant : nicolas.montagne@sorbonne-universite.fr

Reçu : 19 Novembre 2024

Résumé

Les insectes et les plantes à fleurs sont les organismes pluricellulaires les plus abondants et diversifiés sur Terre. Leur évolution est largement interdépendante depuis la fin du Crétacé, où l’explosion de la diversité des plantes a stimulé la diversification des insectes pollinisateurs et herbivores. Les plantes à fleurs sont notamment connues pour émettre dans l’atmosphère un très grand nombre de composés organiques volatils, qui leur permettent d’attirer les insectes pollinisateurs, repousser les insectes herbivores ou attirer les prédateurs ou parasites de ces herbivores. Ces composés servent également de signaux chimiques pour les insectes, les aidant à trouver de la nourriture ou des sites de ponte. La communication chimique a ainsi joué un rôle majeur dans l’histoire évolutive de ces organismes, et la compréhension des mécanismes de cette communication et de leur évolution est l’objet de nombreuses recherches. Des études sont par exemple menées sur la détection des volatils de plantes par le système olfactif des insectes herbivores, et notamment sur l’évolution des récepteurs olfactifs. Ces travaux offrent également des perspectives pour le développement des stratégies de bio-contrôle des ravageurs.

Abstract

Insects and flowering plants are the most abundant and diverse multicellular organisms on Earth, accounting for 75% of known species. Their evolution has been largely interdependent since the so-called Angiosperm Terrestrial Revolution (100–50 Mya), when the explosion of plant diversity stimulated the evolution of pollinating and herbivorous insects. Plant-insect interactions rely heavily on chemical communication via volatile organic compounds (VOCs). These molecules are synthesised by the secondary metabolism of plants through various pathways and include terpenes, benzenoids and aliphatic compounds. As of today, more than 1,700 of these VOCs have notably been identified in flowers. Plants use these molecules to attract pollinators or repel herbivorous insects. VOCs also act as chemical signals for insects, helping them to find food or egg-laying sites. Chemical communication has thus played an important role in the evolutionary history of insects and flowering plants. Tritrophic interactions are a fascinating example of VOC-driven communication. When plants are attacked by herbivores, they emit herbivore-induced volatiles, such as green leaf volatiles and specific terpenes. These signals attract predators or parasitoids of the herbivores, acting as a chemical distress call. For example, parasitoid wasps can identify plants that have been attacked by their host herbivores, even in the absence of the herbivores themselves, thanks to the plant’s odour profile. But herbivore-induced volatiles also affect the herbivores themselves. Female moths, for example, use these olfactory cues to avoid laying eggs on plants that have already been attacked. Insects detect VOCs using highly sensitive odorant receptors on their antennae. Herbivorous insects, such as the model moth species S. littoralis, have receptors specific for floral VOCs and herbivore-induced volatiles. Current research aims to understand how the evolution of these receptors has contributed to the adaptation of insects to plant volatiles. In moths, receptors for benzenoids appear to be more ancient and conserved, whereas receptors for terpenes and aliphatic molecules show more recent diversification in response to plant evolution. Research into plant-insect communication also opens up avenues for sustainable agriculture, as VOCs can be used to attract natural pest predators or deter herbivores, reducing the need for chemical pesticides.