Hormones control various metabolic traits comprising fat deposition or starvation resistance. Here we show that two invertebrate neurohormones, octopamine (OA) and tyramine (TA) as well as their associated receptors, had a major impact on these metabolic traits. Animals devoid of the monoamine OA develop a severe obesity phenotype. Using flies defective in the expression of receptors for OA and TA, we aimed to decipher the contributions of single receptors for these metabolic phenotypes. Whereas those animals impaired in octß1r, octß2r and tar1 share the obesity phenotype of OA-deficient (tβh-deficient) animals, the octß1r, octß2r deficient flies showed reduced insulin release, which is opposed to the situation found in tβh-deficient animals. On the other hand, OAMB deficient flies were leaner than controls, implying that the regulation of this phenotype is more complex than anticipated. Other phenotypes seen in tβh-deficient animals, such as the reduced ability to perform complex movements tasks can mainly be attributed to the octß2r. Tissue-specific RNAi experiments revealed a very complex interorgan communication leading to the different metabolic phenotypes observed in OA or OA and TA-deficient flies.

Monoterpenes are molecules with insecticide properties whose mechanism of action is however not completely elucidated. Furthermore, they seem to be able to modulate the monoaminergic system and several behavioural aspects in insects. In particular, tyramine (TA) and octopamine (OA) and their associated receptors orchestrate physiological processes such as feeding, locomotion and metabolism. Here we show that monoterpenes not only act as biopesticides in Drosophila species but can cause complex behavioural alterations that require a functional type 1 tyramine receptors (TAR1s). Variations in metabolic traits as well as locomotory activity were evaluated in both Drosophila suzukii and Drosophila melanogaster after treatment with three monoterpenes. A TAR1 defective D. melanogaster strain (TAR1PL00408) was used to better understand the relationships between the receptor and monoterpenes-related behavioural changes. Immunohistochemistry analysis revealed that, in the D. melanogaster brain, TAR1 appeared to be mainly expressed in the pars intercerebralis, lateral horn, olfactory and optic lobes and suboesophageal ganglion lobes.In comparison to the D. melanogaster wild type, the TAR1PL00408 flies showed a phenotype characterized by higher triglyceride levels and food intake as well as lower locomotory activity. The monoterpenes, tested at sublethal concentrations, were able to induce a downregulation of the TAR1 coding gene in both Drosophila species. Furthermore, monoterpenes also altered the behaviour in D. suzukii and D. melanogaster wild types 24 h after a continuous monoterpene exposure. Interestingly, they were ineffective in modifying the physiological performances of TAR1 defective flies. In conclusion, it appears that monoterpenes not only act as biopesticides for Drosophila but they can also interfere with its behaviour and metabolism in a TAR1-dependent fashion.

5Monoterpenes are molecules with insecticide properties whose mechanism of action is however not 3 6 completely elucidated. Furthermore, they seem to be able to modulate the monoaminergic system 3 7and several behavioural aspects in insects. In particular, tyramine (TA) and octopamine (OA) and 3 8 their associated receptors orchestrate physiological processes such as feeding, locomotion and 3 9 metabolism. Here we show that monoterpenes not only act as biopesticides in Drosophila species 4 0 but can cause complex behavioural alterations that require a functional type 1 tyramine receptors 4 1 (TAR1s). Variations in metabolic traits as well as locomotory activity were evaluated in both 4 2 Drosophila suzukii and Drosophila melanogaster after treatment with three monoterpenes. A 4 3 TAR1 -/-D. melanogaster strain was used to better understand the relationships between the receptor 4 4 and monoterpenes-related behavioural changes. Immunohistochemistry analysis revealed that, in 4 5the D. melanogaster brain, TAR1 appeared to be expressed in areas controlling metabolism. In 4 6comparison to the D. melanogaster wild type, the TAR -/flies showed a phenotype characterized by 4 7 higher triglyceride levels and food intake as well as lower locomotory activity. The monoterpenes, 4 8 tested at sublethal concentrations, were able to induce a downregulation of the TAR1 coding gene 4 9 6 9