[Un article de The Conversation écrit par Fiorucci Sébastien – Maître de conférences en chimie informatique et théorique, Université Côte d’Azur & Emmanuelle Jacquin-Joly – Directrice de recherche en écologie chimique des insectes, Inrae]
Welcome to the jungle of odors where plants are not as innocent as they seem! When some plants are attacked by a predator, they can appeal to olfactory help. This is the case of corn which, when attacked by the caterpillars of the fall legionnaire, a butterfly causing major damage all over the world, will produce attractive odors for a caterpillar predator: the wasp Insularis cheronus. This small insect then lends a hand to plants by destroying the invaders. For example, alpha-clip, wooded odor used in perfumery, is a clearing key compound of this olfactory war.
Plants are real olfactory defense pros! In addition to calling for help the natural enemies of herbivores, they have other tricks in their bag. Some emit repellent smells to keep harmful insects away, like defense odors who say: “Do not approach, I'm toxic!” “Others produce compounds that attract pollinators, such as odors of seduction who say:” Come here! I have nectar for you. “Plants can even communicate with their neighbors to warn them of an imminent danger, like an olfactory phone that says:” Be careful, insects arrive, prepare your defenses! ” »»
Plants are real strategists of olfactory war, and it smells good for research. Concretely, how do scientists work to exploit these invisible messages to develop new methods of culture protection?
Plant olfactory powers
Like many living things, plants produce volatile organic compounds (VOC). VOCs are molecules that evaporate easily and are released in the air, playing a key role in the communication and defense of plants. When these VOCs can be perceived by insects, other animals or even other plants, and influence their behaviors and interactions, we then speak of semio-chemical compounds. And among these semio-chemical compounds, you may know a category called pheromones, widely used by insects. It is a type of compound acting as a messenger between individuals of the same species, allowing for example the recognition of a sexual partner, acting as an aggregation, alarm, or even social cohesion. Plant signals are called “Kairomones” or “Allomones”, depending on the product profit: the former are useful to the information receiver, the latter to the transmitter. Understanding these chemical interactions can help us develop new insect management strategies, more targeted and more respectful of the environment than conventional synthetic insecticide methods.
Olfactory signals to protect crops
And it is here that research in chemical ecology comes into play. It is science that studies the chemical interactions between living organisms and their environment.
Scientists in this area study these interactions to understand how plants use VOCs to influence their environment. By analyzing the odors issued by plants, they can identify the key molecules which act on the behavior of insects. Researchers thus develop methods to reproduce and amplify the chemical signals of plants, aimed at deceiving harmful insects.
The olfactory traps based on attractive odors that you may have in your garden, or the repellents you use to push mosquitoes, wasps, hornets are precisely inspired by research in chemical ecology. You may have already tried to get rid of food mites in your kitchen using glue plates flavored with the sexual pheromone of this little butterfly whose larvae are invited in our flours, rice, pasta or dried fruits.
The search for effective smells is not, however, an easy task, given the immensity of the chemical signals issued by plants. An complementary approach that we develop, called inverse chemical ecology, allows a shortcut. This new approach focuses on the insect detection system, and in particular on their “olfactory sensors”, also called olfactory receivers, which are on their sensory organs.
By understanding how these receptors work, we can precisely identify what they are capable of detecting in the vast universe of plant VOCs, and odors in general. Let us take for example the cotton night which, as its name does not indicate, actually attacks a wide variety of cultures mainly in the south of the Mediterranean basin and in Africa, and today represents an invasive threat in France. The study of one of its olfactory receivers has enabled us to identify new unsuspected attractive.
This fine understanding makes it possible to develop new molecules capable of targeting the natural functioning of key olfactory receptors in a targeted way and to widen the spectrum of effective semi-chemicals, without disturbing neighboring insects. The inverse chemical ecology thus makes it possible to accelerate the development of methods of protection of targeted cultures and more respectful of the environment, while reducing the unintentional impacts on other species.
Our research projects exploit this knowledge for applied purposes in agriculture. The Ardeco project, for example, aims to develop a national infrastructure distributed in chemical ecology to anticipate the withdrawal of phytosanitary substances and promote alternative techniques for culture protection. In addition, the Invoria project, seeks to unravel the mysteries of insect olfactory receivers using an innovative approach combining artificial intelligence and broadband experiment. The expected repercussions are important for the protection of cultures, but also for human and animal health, pollination and bioconching.
By exploiting the power of odors, scientists participate in the development of promising alternatives to chemical pesticides, thus contributing to more sustainable agriculture and the preservation of biodiversity.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
