Azadirachtin impact on mate choice, female sexual receptivity and male activity in Drosophila melanogaster (Diptera: Drosophilidae)

Azadirachtin exposure inhibit ovary development of Spodoptera litura (Lepidoptera: Noctuidae) by altering lipids metabolism event and inhibiting insulin signaling pathways

Lipids are main energy source for insects reproduction, which are becoming emerging target for pest management. Azadirachtin (AZA) is a multi-targeted and promising botanical insecticide, but its reproduction toxicity mechanism related to lipids metabolism is poorly understood. Here, we applied lipidomic and transcriptomic to provide a comprehensive resource for describing the effect of AZA on lipids remodeling in ovary of Spodoptera litura. The results showed that AZA exposure obviously altered the contents of 130 lipids subclasses (76 upregulated and 54 downregulated). In detail, AZA exposure changed the length and saturation degrees of fatty acyl chain of most glycerolipid, phospholipid and sphingolipid as well as the expression of genes related to biosynthesis of unsaturated fatty acids and fatty acids elongation. Besides, following the abnormal lipids metabolism, western blot analysis suggested that AZA induce insulin resistance-like phenotypes by inhibiting insulin receptor substrates (IRS) /PI3K/AKT pathway, which might be responsible for the ovary abnormalities of S. litura. Collectively, our study provided insights into the lipids metabolism event in S. litura underlying AZA exposure, these key metabolites and genes identified in this study would also provide important reference for pest control in future.

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules and Activities: Part Ⅰ (Aphanamixis-Chukrasia)

Plant-originated triterpenes are important insecticidal molecules. The research on insecticidal activity of molecules from Meliaceae plants has always received attention due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discuss 102 triterpenoid molecules with insecticidal activity of plants of eight genera (Aglaia, Aphanamixis, Azadirachta, Cabralea, Carapa, Cedrela, Chisocheton, and Chukrasia) in Meliaceae. In total, 19 insecticidal plant species are presented. Among these species, Azadirachta indica A. Juss is the most well-known insecticidal plant and azadirachtin is the active molecule most widely recognized and highly effective botanical insecticide. However, it is noteworthy that six species from Cedrela were reported to show insecticidal activity and deserve future study. In this paper, a total of 102 insecticidal molecules are summarized, including 96 nortriterpenes, 4 tetracyclic triterpenes, and 2 pentacyclic triterpenes. Results showed antifeedant activity, growth inhibition activity, poisonous activity, or other activities. Among them, 43 molecules from 15 plant species showed antifeedant activity against 16 insect species, 49 molecules from 14 plant species exhibited poisonous activity on 10 insect species, and 19 molecules from 11 plant species possessed growth regulatory activity on 12 insect species. Among these molecules, azadirachtins were found to be the most successful botanical insecticides. Still, other molecules possessed more than one type of obvious activity, including 7-deacetylgedunin, salannin, gedunin, azadirone, salannol, azadiradione, and methyl angolensate. Most of these molecules are only in the primary stage of study activity; their mechanism of action and structure–activity relationship warrant further study.

Effect of bio-insecticide residues and the presence of predatory cues on mating in a biocontrol spider

Insecticide formulations can cause mortality in natural enemies or have sublethal effects on them, which include alterations in their behaviour and development. Here, we investigated the effect of a bioinsecticide (azadirachtin) and predator cues on mating in a biocontrol spider, Philodromus cespitum. Firstly, adult males were exposed to cues from ants (as predators) or conspecific juveniles (as controls) and those from virgin adult females combined with insecticide residues and we then recorded their selection of the respective surfaces. In an insecticide-free environment, males spent significantly more time on the surface with cues from juveniles and virgin females than on the surface with cues from ants and virgin females. In the environment with ant cues, males did not spend significantly more time on the surface treated with water or insecticide residues. Secondly, adult male and female spiders were exposed to cues from predators and conspecifics and fresh insecticide residuals and we recorded mating behaviour. The presence of ant cues nor the presence of insecticide residues had a significant effect on the mating behaviour. However, the frequency of females biting males was significantly lower on the surface with insecticide residues and ant cues and highest on the surface with ant cues and water treatment. The size of mating plugs (applied to female genitals by males during mating) was not different between ant cues and control, but the plugs were significantly larger on the surface with insecticide residues. We conclude that azadirachtin affected only slightly the perception of predation risk and consequently mating behaviour in P. cespitum. Similarly, presence of ant cues had little effect on mating.

Pre-imaginal exposure to Oberon® disrupts fatty acid composition, cuticular hydrocarbon profile and sexual behavior in Drosophila melanogaster adults

Oberon® is a commercial formulation of spiromesifen, a pesticide inhibitor of lipid biosynthesis via acetyl CoA carboxylase, widely used in agricultural crop protection. However, its mode of action requires further analysis. We currently examined the effect of this product on Drosophila melanogaster as a non-target and model organism. Different concentrations of spiromesifen were administered by ingestion (and contact) during pre-imaginal development, and we evaluated its delayed action on adults. Our results suggest that spiromesifen induced insecticidal activity on D. melanogaster. Moreover, spiromesifen treatment significantly increased the duration of larval and pupal development at all tested concentrations while it shortened longevity in exposed males as compared to control males. Also, pre-imaginal exposure to spiromesifen quantitatively affected fatty acids supporting its primary mode of action on lipid synthesis. In addition, this product was found to modify cuticular hydrocarbon profiles in exposed female and male flies as well as their sexual behavior and reproductive capacity.

[Azadirachtin, a natural pesticide with multiple effects]

There are many studies devoted to the negative impact of conventional pesticides that effectively control pests, but cause widespread environmental pollution. As a result, interest is growing in pesticides of a natural origin with a lower environmental impact. Among them, azadirachtin, sold under various formulations (neem oil, Neem-Azal, Bioneem, etc.), is still the most widely recommended molecule in agricultural ecosystems. Azadirachtin has also been used in traditional medicine for centuries, and studies published over the past few years have tended to support its therapeutic use. Yet the argument that azadirachtin is harmless to the environment has been offset by its notable collateral and controversial effects on non-target organisms. The present paper summarizes the work already done in this field.

Azadirachtin acting as a hazardous compound to induce multiple detrimental effects in Drosophila melanogaster

Azadirachtin, a tetranortriterpenoid botanical insecticide, has varied sub-lethal effects against many insect pests, including antifeedant, repellent, and growth regulatory. Despite extensive studies of the mechanisms that underline these physiological effects, little attention has been given to multiple toxic effects of azadirachtin under a coherent concentration, and there is no definitive overarching consensus on its toxicity. Here, we investigated multiple sub-lethal effects induced by 4 mg L^-1 of azadirachtin, which did not elicit antifeedant behavior in Drosophila melanogaster, on metrics of longevity, development, compound eyes and reproduction. Exposure to <20 mg L^-1 azadirachtin did not induce mortality, and 4 mg L^-1 of azadirachtin could shorten lifespan, expression of detoxification genes and activities of related detoxification enzymes were higher. The lower activity of chitinase and higher content of chitin in fruit fly exposed to 4 mg L^-1 azadirachtin could be important in developmental inhibition effects, and ovarian abnormalities and lower fecundity could have resulted from azadirachtin-mediated influences on juvenile hormone and ecdysone that disrupted the endocrine system. Caspase-3, head involution defective and reaper-dependent apoptosis genes may have been responsible for compound eye abnormalities in flies exposed to azadirachtin. Our findings provide important insights to the potential mechanisms of sub-lethal effects of azadirachtin.