Journal of Chemical Ecology最新文献

Propolis, a sticky resinous material gathered by bees from various plant sources such as tree buds, sap flows, and other botanical exudates, is renowned for its remarkable biological properties, extensively used in the treatment of several illnesses and for its positive impact on human health. Propolis has been linked to a variety of health advantages, including antiviral, antibacterial, antioxidant, antifungal, anticancer, and anti-inflammatory effects. These benefits are attributed to its rich content of flavonoids, aromatic acids, and phenolic compounds. This study examined the composition of stingless bee propolis using sophisticated analytical techniques, GC-HRMS and LC-HRMS analysis. The analysis unveiled that the primary chemical classes present in the propolis were acids, fatty acids, steroids, alcohols, amines, amino acids, flavonoids, terpenoids, chalcones, aldehydes, ketones, benzene, coumarin, pterocarpan, ether, and ester. Components commonly identified across all locations included:syringic acid, and ellagic acid (acids), punicic acid, 9,10-dihydroxystearic acid, and phloionolic acid (steroids and fatty acids), thevetiaflavone, luteolin, and quercetin (flavonoids), octadecanamine and oleamide (amines), ursolic acid and oleanolic acid (terpenoids), 5-[(z)-pentadec-8-enyl] benzene-1,3-diol (alcohols), dihydrocordoin and orotinichalcone (chalcones). The predominant components identified in the propolis of location 1 and location 3 was 20S, 24S-dihydroxy dammer-25-en-3-one, whereas it was glycyrrhizic acid in location 2 and location 4.

Attracting a mate at the right time is critical for many species that reproduce sexually. In insects, short-range communication between potential mates is often mediated by cuticular hydrocarbons (CHCs), which cover most of the insect cuticle. Although the CHC profiles of many insects have been studied, we know little about what aspects of a CHC profile cause changes in mate attractiveness over the lifetime of an individual. We addressed this question by studying the mason wasp Odynerus spinipes, whose females exhibit age-related quantitative changes in their CHC profile composition. First, we created an ethogram of the male mating behavior. We observed in preliminary investigations that males do not attempt to mate with recently eclosed adult females. By coating wasp dummies with different CHC extracts, we were able to show that the CHC profiles of 0-day-old females are indeed less attractive to males than those of 3-day-old females. CHC profiles of 3-day-old females are characterized by significant decrease of the relative abundance of methyl-branched alkanes. These results, along with the consistently high relative abundance of methyl-branched alkanes in the CHC profile of males throughout their adult lifetime, suggest that in O. spinipes, methyl-branched alkanes may function as anti-aphrodisiacs. They likely reduce the harassment of females before they are ready to mate and help to prevent homosexual courtship.

Alarm behaviors have been widely studied in social insects such as termites, ants, honeybees and stingless bees. As part of this behavior, it is well known that alarm pheromones play a crucial role in recruiting nestmates to defend the colony. Despite the acknowledged phylogenetic proximity between bumblebees, honeybees and stingless bees, there is no evidence indicating the presence of alarm pheromones in bumblebees of the genus Bombus. Herein, during experiments involving Bombus pauloensis foragers under perceived threat, we detected a strong odor, prompting us to investigate the composition of the released secretion. By means of Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry, we found more than 20 volatile compounds, with 2-Heptanone and both enantiomers of Rose oxide being more predominant. These volatiles were quantified. In addition, to determine the secretion source, we evaluated the antennal response to odors coming from different dissected body parts (e.g., head, mandibles, sting) of foragers, and found that the responses were significantly different to odors coming from the dissected mandibles. Our results provide the first chemical description of a particular repulsive blend released by bumblebee foragers when threatened. In this study, we leverage our understanding of B. pauloensis chemical communication in order to glean new insights into potential shared and elaborated mechanisms mediating social organization across bumblebee species.

Biological control agents heavily rely on volatile cues for host location and can be an important component of managing pests through habitat management-based strategies that enhance trophic interactions. This study aimed at evaluating the influence of greenleaf desmodium (Desmodium intortum (Mill.) Urb. (Fabaceae) infochemicals on the behaviour of three select parasitoids of kale pests (aphids and Diamondback moth), to determine the potential of enhancing the protection of vegetables in integrated push-pull cropping systems. To achieve this, the volatile-mediated behavioural responses of the parasitoids towards D. intortum volatiles were evaluated using a dual-choice Y-tube olfactometer. Our results showed that Cotesia vestalis (Hymenoptera: Braconidae), a parasitic wasp for Diamondback moth (DBM) (Plutella xylostella (Linneaus)) was not attracted to volatiles from D. intortum compared to DCM and empty oven bag controls. Nevertheless, D. intortum VOCs elicited higher parasitoid activity, whether in dual-choice comparisons with either empty oven bags or DCM controls, or when paired with kale plants. Conversely, volatiles from D. intortum were highly attractive to Aphidius colemani (Viereck) (Hymenoptera: Braconidae), a parasitic wasp of aphids. Interestingly, another aphid parasitic wasp, Aphidius ervi (Haliday) (Hymenoptera: Braconidae) was attracted to volatiles from D. intortum only when paired with kales or by kales alone. Gas-chromatography mass spectrometry of D. intortum headspace volatiles revealed 16 compounds: hexanal, (Z)-3-hexenol, p-xylene, o-xylene, nonane, α-pinene, cumene, octen-3-ol, octanone, (Z)-3-hexenyl acetate, sabinene, (E)-β-ocimene, linalool, β-elemene, (E)-β-caryophyllene and an unknown compound. In electroantennography assays, all parasitoid antennae commonly detected hexanal and, (E)-β-ocimene, whilst only C. vestalis and A. ervi registered common antennal responses to (E)-β-caryophyllene. Additionally, the antennae of A. colemani detected cumene, octen-3-ol, (Z)-3-hexenyl acetate and an unknown compound whilst that of A. ervi and C. vestalis detected (Z)-3-hexenol and nonane, respectively. Dose-response olfactometer bioassays with the synthetic standards of hexanal, (E)-β-ocimene and (E)-β-caryophyllene revealed that the response of the three parasitic wasps varied with the concentrations of the individual standards. Specifically, (E)-β-ocimene and hexanal depicted a broad appeal to the tested parasitoids, by eliciting attraction at varying concentrations (P < 0.05). However, (E)-β-caryophyllene was selectively attractive to A. ervi, with no significant attraction observed in C. vestalis (P > 0.05). Our results show species- and -context -specific parasitoid attractive appeal of D. intortum. Nevertheless, our results show that D. intortum may help protect kales against aphid attack through parasitoid recruitment whilst another mechanism may be employed against DBM moth.

The defensive secretions of the millipede, Coxobolellus saratani Pimvichai, Enghoff & Backeljau, 2022 were analyzed by gas chromatography-mass spectrometry to provide the very first data on the composition of the defensive secretions of the family Pseudospirobolellidae (Diplopoda: superorder Juliformia, order Spirobolida). This unveiled at least 12 identifiable compounds, including six quinones, two phenols, and four fatty acid esters. The three most prevalent identifiable compounds were 2,3-dimethoxy-1,4-benzoquinone (25.52%), hexyl pentadecanoate (11.57%) (the first report of a fatty acid ester compound in the order Spirobolida and tentatively indicating that this may be a shared feature of the Juliformia), and 3,4-dimethoxyphenol (10.51%). The antimicrobial activity of the defensive secretions was evaluated against three gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, and S. aureus DMST20654), four gram-negative bacteria (Escherichia coli, E. coli ATCC25922, Pseudomonas aeruginosa, and Salmonella ser. Typhi ATCC16122), and two yeast strains (Candida albicans and C. albicans ATCC10231). The antibiotic kanamycin and the antifungal drug fluconazole were employed as positive controls. Paper disc diffusion assays demonstrated that the fresh, undiluted, secretions inhibited the growth of all tested microorganisms. Furthermore, broth microdilution analysis revealed Minimum Inhibitory Concentrations (MIC) ranging from 40 to 20,000 µg/mL and Minimum Bactericidal/Fungicidal Concentrations (MBC/MFC) ranging from 1,250 to > 20,000 µg/mL. The MIC values indicated that the defensive secretions of C. saratani are notably more efficient than kanamycin and fluconazole in inhibiting the growth of S. aureus DMST20654, E. coli ATCC25922 and C. albicans, but inhibit less effectively the visible growth of the six other microbial taxa tested. Finally, the MBC/MFC values revealed that the secretions of C. saratani may show less potent antimicrobial activity against the nine microbial taxa tested than kanamycin and fluconazole. Nevertheless, these results suggest once more that millipede defensive secretions may not only deter predators, but may also provide millipedes with a chemical defense against pathogens and parasites.

Several crops are threatened by pollinator-vectored plant pathogens, which can reduce fruit yield and quality. Domestication has frequently increased crop susceptibility to plant pathogens, but significant cultivar variation in resistance typically exists. While it is well known that floral traits can shape plant-pollinator-pathogen interactions in natural and managed systems, little is known regarding how morphological, phenological, and chemical traits combine to shape resistance in domesticated plant species. Here, we address this topic by (1) conducting a common garden field experiment where we measured percent of tissues infected by the fungal pathogen Monilinia vaccini-corymbosii in 14 cultivars of highbush blueberries (Vaccinium spp.) and (2) using a three-pronged multivariate approach of PCA, random forest, and LASSO regressions to single out predictors of cultivar resistance from a suite of phenological, morphological, and chemical (oxidatively active phenolics) traits collected from the field. Leaf and floral traits varied between cultivars, and we found that concentrations of phenolics (chlorogenic acid and total phenolics) in leaves were strong predictors of cultivar resistance to the primary infection stage of M. vaccini-corymbosii, while floral phenology and carpel phenolics (procyanidin-containing proanthocyanidins and quercetin derivatives) predicted resistance to the secondary infection stage. Our findings highlight that intraspecific variation in chemical and phenological traits as a result of breeding can shape plant-pollinator-pathogen dynamics. This information could be used in future trait-based breeding efforts to increase resistance to disease.

The emission of volatile organic compounds (VOC) in plants can be influenced by abiotic factors such as light, temperature and moisture, as well as biotic factors like herbivory, oviposition, and pathogen damage. The influence of symbiotic microorganisms on VOC emission is less explored. Although it is widely known that arbuscular mycorrhizal (AM) fungi can significantly affect host plant metabolism, their role in VOC emission in trees remains under-investigated. Here, we examine the impact of AM fungi on VOC production in the South American willow tree, Salix humboldtiana. We assessed the effects of inoculation with AM fungi on plant growth and larval feeding by the willow sawfly Nematus oligospilus, as well as its impact on the plant's VOC emission profile. Willow plants inoculated with AM fungi exhibited increased leaf biomass and reduced damage incidence from willow sawfly larvae, supporting the role of mycorrhiza as a protective symbiosis. Notably, AM fungi-inoculated plants emitted 40% less total VOC compared to non-inoculated plants. Both groups emitted similar levels of monoterpenes; however, inoculated plants produced 30% fewer sesquiterpenes. Herbivory did not alter total VOC emission, but non-inoculated plants showed a reduction in (E)-β-ocimene, which was not observed in inoculated plants. The significant decline in sesquiterpene emission of inoculated willow saplings points out the importance of considering the symbiotic microorganisms in the study of plant defenses and insect-plant interactions.

Low Red (R) to Far Red (FR) light ratios, a light signal associated with vegetation shade, can prompt intact maize (Zea mays) plants to constitutively emit more volatiles when exposed to herbivory-induced plant volatiles (HIPVs). Here we investigated how simulated shading affects priming responses in the context of volatile-mediated plant-plant interactions. Receiver maize plants were exposed to either constitutive volatile organic compounds (cVOCs) or HIPVs from emitter maize plants, while we manipulated R: FR light conditions of receivers or emitters. Priming responses in the receivers were then assessed by measuring real-time volatile emissions following simulated herbivory. We show that low R: FR light enhances HIPVs emissions in plants previously exposed to HIPVs from neighbours independently of the light conditions of emitters. We also demonstrate that both cVOCs and HIPVs emitted by maize grown under low R: FR amplify HIPVs emissions in their neighbours. This amplified response could not be explained by FR-mediated changes in the release of green leaf volatiles or terpenoids by emitters, thus suggesting the involvement of other VOCs. We conclude that volatile-mediated plant-plant interactions can be expected to become more intense in denser canopies due to light-mediated amplification of volatile emission and responsiveness.