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BIONÆR-Bionæringsprogram

Chemosensory pathways underlying oviposition behavior in the pest insect, Helicoverpa armigera - peripheral and central mechanisms

Alternative title: Kjemosensoriske baner knyttet til eggleggingsadferd i skadeinsektet, Helicoverpa armigera - perifere og sentrale mekanismer

Awarded: NOK 10.8 mill.

Project Number:

324379

Application Type:

Project Period:

2021 - 2025

Funding received from:

Partner countries:

Pest insects feeding on cultivated crops have been a substantial challenge for man from ancient times. The devastating locust swarms attacking agriculture in the Nile Valley, as described in the books of Moses (ca. 1405 bp), is one of the first written references to this problem. The major aim of the project presented here is to contribute to world food safety by exploring basic principles associated with odor-regulated egg-laying behavior in one of the globally most harmful pest insects - the noctuid moth, Helicoverpa armigera (cotton bullworm). So far, the ongoing project has contributed essentially to increasing the knowledge about chemosensory pathways linked to a type of female-specific reproductive behavior in the relevant species, H. armigera. As described in a new publication in the internationally renowned journal, Current Biology, we have – in collaboration with our Chinese partners - identified an odor receptor on the female's antennae, HarmOR56, which affects egg-laying behavior in pregnant individuals. Thus, the data shed light on the previously well-described biological phenomenon of pregnant females avoiding plants/areas that are already covered with eggs. Activation of the newly identified receptor, which detects so-called oviposition deterrents (ODs) in the form of three methyl esters released from the surface of the species' eggs, inhibits egg laying behavior. The study explains, for the first time, how a female-specific olfactory receptor recognizes chemical signals from conspecific eggs. Notably, while olfactory pathways linked to reproduction have been thoroughly described in H. armigera males, nothing has been reported on a female-specific system linked to reproduction - until now. Experimental methods used in the described publication include CRISPR/Cas9 gene editing, extracellular recordings, and behavioral studies. In the remaining part of the project period, we will describe how the information from the specific ODs is coded in the central olfactory pathways. Via intracellular recordings/stainings and calcium imaging measurements, we will identify anatomical and physiological characteristics of a female-specific brain network linked to reproduction. Parts of this work have already been presented at various scientific conferences.

For establishing sustainable agriculture and safe food production, the human society must change pest control strategies by reducing utilization of chemical pesticides and replacing them with environment-friendly alternatives. Despite introduction of biological strategies already several decades ago, including utilization of the insects' own odor signals, such as sex-pheromones, the effectiveness of these methods needs to be improved. It is therefore urgent to upgrade the knowledge about the olfactory pathways and the relevant signaling mechanisms. In this assignment, we aim to explore a system yet poorly described – i.e., the chemosensory circuit underlying regulation of female-specific egg laying behavior in the global pest insect, Helicoverpa armigera. The new knowledge may pave the way for innovation of novel pest control methods approaching the harmful larvae directly. This proposal is linked to an ongoing research project on food safety, classified within the Sino-Norwegian program of the Research Council of Norway (RCN). Three recent high-ranked articles from our research unit on the ongoing project, entitled “Plant – insect relationships: imaging CO2, pheromones, and plant odors in the olfactory pathway of an herbivorous insect”, proves the academic ability of the Chemosensory lab and the suitability of the basic research approach. By continuing the well-established cooperation with our Chinese partners and including a national collaborator having extensive experience from applied research projects on the relevant topic, we have an ideal base for the new plan. The project will include behavioral tests of the local pest species, Pieris brassicae, as well. Regarding expert knowledge, the distinct groups complement each other perfectly as the Norwegian units are competent to explore the central pathways and the odor evoked behaviors, respectively, while the Chinese can uncover details of the peripheral signaling pathway.

Publications from Cristin

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Funding scheme:

BIONÆR-Bionæringsprogram