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BIONÆR-Bionæringsprogram

Plant - insect relationships: imaging CO2, pheromones, and plant odors in the olfactory pathway of an herbivorous insect

Alternative title: Insekt - plante relasjoner: avbildning av CO2, feromoner og plantedufter i herbivore insekters luktebaner

Awarded: NOK 5.0 mill.

Evolution of insect-plant relationships has been one of the central topics of science for more than 150 years. Charles Darwin pointed out the interplay between flowering plants (angiosperms) and plant-eating (herbivore) insects as early as 1859, in Origin of Species. In fact, when Darwin saw the long trail of an orchid from Madagascar, he predicted the existence of a pollinating night heron with a very long suction beak. Final evidence for the cow evolution that includes the orchid and the long-tongued moth, named Xanthopan morganii praedicta, did not appear until the 1990s. It is generally accepted that angiosperms, which originated 130 million years ago, required specialized pollinators. Even in our time, most flowering plants are pollinated by insects. Thus, in terms of interactions with blooming organisms, insects are the most important group of terrestrial animals. Agriculture, which is closely linked to angiosperms, is therefore fundamentally dependent on these small organisms. On the other hand, however, certain herbivorous insects represent a serious problem for agriculture just because of their impact as plant-feeders. Even though these pests make up only 1% of all insects, they are responsible for a significant loss of crops. For establishing a sustainable agriculture, it is necessary to minimize the extent of pests and at the same time preserve the insects' biological diversity. This requires, above all, increased knowledge about insects. We have just entered the third and final year of this research project where we study the olfactory system of the noctuid moth, Helicoverpa armigera. In our latest scientific article, published in the internationally renowned journal eLife, we present how female-produced olfactory signals, associated with attraction and rejection, respectively, are encoded in the higher brain centers of the male (https://elifesciences.org/articles/65683). Here, the two categories of scent signals, each associated with a specific behavior, are represented in separate areas. These findings provide new insight into male-specific olfactory pathways associated with reproductive behavior in one of the most serious pests globally. In two previous articles from the ongoing project, we mapped the specific route for CO2 input, which in turn is significantly integrated with the olfactory pathway devoted to nutritional intake. In addition to increasing the general knowledge of insect neurobiology, this type of data on chemosensory systems is important to replace the use of traditional pesticides with control mechanisms based on biologically relevant signals.

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In this joint proposal including research groups at the Chinese Academy of Agricultural Sciences, Beijing; Henan Agricultural University, Zhengzhou; and Chemosensory laboratory, Norwegian University of Science and Technology (NTNU), we will extend our already well established cooperation on the olfactory system of a plant feeding insect representing one of the worldwide pests. The fruitfulness of this cooperation has been demonstrated by numerous international publications. The expert competence in the distinct groups complements each other in an optimal manner as the Chinese groups focus on the peripheral arrangement of the insect's chemosensory system and the Norwegian group on the central pathways. For establishing a sustainable agriculture, the human society has to balance between the two factors of preserving biodiversity of pollinating insects and at the same time minimizing the extent of pests. Therefore, the knowledge about insects in general and pest species specifically is utterly important. In this assignment, we aim to explore chemosensory signal processing including CO2, plant odors, and pheromones in the noctuid moth, Helicoverpa armigera. As larvae, these organisms damage reproductive organs of important crops. Adult insects measure CO2 emission from plants in search for optimal hosts. This ability is based on a specific gaseous-sensing organ located on the tip of two mouthpart structures. The project presented here, includes three work packages (WPs), each of which corresponds to distinct levels of the chemosensory pathway: 1) WP1 to detection and processing at the peripheral level, 2) WP2 to coding principles in the primary olfactory center (the antennal lobes), and 3) WP3 to modulation of odor-evoked behavior. In addition to the scientific outcome in the form of publications and presentations, this project will contribute to regulate populations of insect pests in an environmentally sound way.

Publications from Cristin

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BIONÆR-Bionæringsprogram