Journal of Chemical Ecology最新文献

Although sessile, plants have sophisticated systems of perceiving their environment. They respond to biotic and abiotic stress, for instance, they can detect damage caused by insect feeding or oviposition and respond by releasing volatile compounds, known as herbivore- or oviposition-induced plant volatiles (HIPVs or OIPVs). The corn leafhopper, Dalbulus maidis (DeLong and Wolcott), is a sap-sucking insect that has been causing challenges to maize growers across the Americas by transmitting phytopathogens that cause substantial production losses. In this study, we evaluated whether maize plants modify their volatile emissions in response to different densities of pathogen-free D. maidis adults, the type of injury, and varying injury durations at two distinct vegetative stages. The results showed that injury caused by corn leafhoppers induced the release of HIPVs and OIPVs, with the response influenced by the plant stage, insect density, type of injury and injury duration. Density primarily affected the quantity of volatile induction, injury duration shaped the induced blend, and plant stage influenced all these aspects. Consistently induced compounds by all the factors tested included (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), (E)-β-caryophyllene, and (E)-β-farnesene. Whereas the oviposition injury induced only two volatiles: nonanal and decanal. This study highlights how maize respond with different blend profile of HIPVs and OIPVs, demonstrating that maize adapts its volatile emissions depending on the intensity of stress it has been submitted. These findings can be further explored in multitrophic interactions, potentially influencing natural enemies that utilize these volatiles as cues in the environment.

Aphid-tending ants form mutualistic associations with aphids. During their interactions, aphids and ants use both tactile stimuli and chemical cues to communicate. Recent studies suggest that ants modify the cuticular hydrocarbons of mutualistic aphids they attend, but it is unclear which compounds are implicated in recognition. Thus, we investigated the chemical basis for the discrimination between attended and unattended aphids, Aphis gossypii Glover (Hemiptera: Aphididae), by the ant Tapinoma ibericum (Santschi, 1925) including cuticular hydrocarbons (CHCs and non-CHCs) compounds in the analysis. Chemical profiles of 14 colonies of A. gossypii attended by ants for three days were significantly different from those of unattended aphids. These results show that contact with T. ibericum rapidly induces modification of the cuticular profiles of the aphids on which they feed. Moreover, the compounds of unattended aphid A. gossypii also change over time but differ from those of attended aphids. The main compound of the ant cuticle (3,15-di-MeC27), which is highly abundant in attended aphids, was identified as a possible recognition marker, but without forgetting other identified compounds that may also play a predominant role in the ant-aphid mutualistic interactions. These promising compounds represent opportunities for pest control strategies using chemical manipulations.

Domestication often alters plant traits, leading to cascading effects on ecological interactions, particularly in tri-trophic relationships among plants, herbivores, and their natural enemies. While recent studies have investigated the influence of domestication on plant-derived food sources, its effect on guttation-a nutrient-rich exudate produced by many plants-remains unexplored. In this study, we examined the effects of guttation droplets from wild and cultivated highbush blueberries on the fitness (longevity and fecundity) and feeding preferences of three insect species from different trophic guilds: an herbivore (Drosophila suzukii), a parasitoid (Trichopria drosophilae), and a predator (Chrysoperla carnea). Additionally, we analyzed and compared the size and nutritional composition-specifically, total sugar and protein content-of guttation droplets between wild and cultivated blueberry plants. Our results indicated that guttation from wild plants enhanced the longevity of all three insect species, often surpassing that of cultivated plants and diets containing only sugar or sugar plus protein. In choice assays, all three insect species consistently preferred guttation from wild plants over that from cultivated ones. Although the guttation droplets from cultivated plants were larger, those from wild plants contained higher concentrations of sugars (six times more) and proteins (five times more), which likely contributed to the insects' enhanced fitness and preference for wild plant guttation. These findings indicate that domestication has reduced the ecological functionality of guttation in blueberries by potentially influencing tri-trophic interactions. Understanding how domestication affects plant-derived food sources like guttation could have important implications for the conservation of natural enemies in agricultural landscapes.

Millipedes have developed specialized chemical defenses against predators and parasites. Here we investigated the strong repellent odour emitted by two julids from the Caucasus, Syrioiulus continentalis (Attems, 1903) and Pachyiulus krivolutskyi Golovatch, 1977. By NMR and GC-MS, as well as compound synthesis, we identified the major compound in the secretions of both species as 4-ethylhex-1-en-3-one. A second compound was tentatively identified as the dimer of the main compound as 2-ethyl-1-(6-(pentan-3-yl)-3,4-dihydro-2H-pyran-2-yl)butan-1-one. Both compounds amounting for more than 95% of the whole secretion. 4-Ethylhex-1-en-3-one was found for the first time as a naturally occurring compound, and due to its identification in millipedes of the order Julida we propose here the trivial name "julidone". Considering current knowledge, the replacement of the juliform quinones by novel components such as ketones appears to be highly derived conditions in the chemistry of Julida, possibly triggered by different environmental challenges arising from the epigeic life-style of the two species.

Herbivores are frequently exposed to potentially toxic doses of plant secondary metabolites (PSMs). Furthermore, the plant species available and their associated PSMs may change over extended time periods. To understand the ability of herbivores to biotransform novel PSMs, we investigated populations of one species of mammalian herbivore that had undergone a radical diet shift, i.e., the desert woodrat's (Neotoma lepida) switch juniper (Juniperus spp) to creosote bush (Larrea tridentata). To determine whether woodrats currently feeding on creosote also retain the ability to consume and biotransform the PSMs in their ancestral diet of juniper, we compared various metrics of hepatic biotransformation in a population that ingests creosote bush (Mojave woodrats) to one that specializes on the ancestral diet of juniper (Great Basin woodrats). We investigated PSM biotransformation capabilities by quantifying the hepatic metabolism of α-pinene, a common terpene in juniper. We also measured total cytochrome P450 content, cytochrome P450 2B (CYP2B) and glutathione S-transferase (GST) concentrations, and the activity of GST in the livers of both populations consuming control (rabbit chow) and juniper diets. There were no differences in hepatic metabolism of α-pinene, total P450 content, or CYP2B concentration between woodrat populations when feeding on juniper. The only difference found was that the Mojave woodrats had higher GST activity compared to the Great Basin woodrats when feeding on juniper. Our results suggest that despite the change to a novel toxic diet, the Mojave woodrats maintain the capacity to metabolize their ancestral diet of juniper.

Tomato, a globally significant crop, faces continuous threats from pests and pathogens, necessitating alternative approaches to reduce chemical inputs. Beneficial soil microbes, such as arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR), offer promising solutions by enhancing plant growth and pest tolerance. However, domestication may have weakened tomatoes' interactions with these microbes, potentially compromising their innate immunity, a hypothesis that remains largely unexplored. To address this gap, we examined the effects of AMF and PGPR inoculation on growth, herbivory resistance, and metabolic responses in the domesticated Solanum lycopersicum 'Moneymaker' and three wild tomato relatives. Our findings reveal that microbial inoculation significantly influences both domesticated and wild tomatoes, with PGPR generally enhancing and AMF reducing plant growth across species. Using targeted and untargeted metabolomics, we found that soil microbes substantially alter plant chemistry above- and belowground in a species-specific manner. Notably, herbivore responses were more affected by AMF presence than by tomato species. These results highlight that while domestication has profoundly shaped tomato traits, microbial interactions can modulate these phenotypes. Thus, selecting microbial strains best suited to modern cultivars is crucial for optimizing plant growth and resilience against pests.

Given the multiple possible mechanisms for interspecific chemical interaction between adjacent heterospecific plants, phytochemical profiles, which include phytochemical defense compounds, of crop species could potentially be enhanced or altered by intercropping with phytochemically diverse neighbors. We assessed the influence of intercropping between phytochemically diverse plants on plant biomass and aerial volatile organic compound (VOC) emission profiles by intercropping sweetclover (Melilotus alba) and wheat (Triticum aestivum) with silflower (Silphium integrifolium) in AMF-inoculated soil. We also assessed the impact of intercropping on induced VOC profiles by conducting an in-situ, no-choice bioassay with fall armyworm (Spodoptera frugiperda). Of eight compound classes we identified across the three plant species, prenol lipids (terpenoids) were upregulated in silflower plants when monocropped with wheat and when herbivory was introduced. Carboxylic acids and organooxygen compounds were reduced in sweetclover when intercropped with silflower, but increased under herbivory. Uninfested wheat plants emitted more organooxygen compounds and fatty acyls than infested plants when intercropped with silflower, but not when monocropped. Wheat and sweetclover biomass increased when intercropped with silflower, but silflower biomass was unaffected by intercropping. This study showed that VOC emissions of plants from three diverse taxa are altered by both intercropping and herbivory in ways that may impact their resistance to insect herbivory. Further research into the role of intercropping on volatile profile emissions, and possible pest resistance in agroecological systems, could help farmers to design intercropping systems that optimize natural plant herbivory defenses, thus improving agricultural sustainability.

The small white butterfly Pieris rapae is a major pest of brassicaceous crops, causing extensive damage to cabbage Brassica oleraceae var. capitata. Pieris rapae utilizes glucosinolates, which are characteristic of brassicaceous plants, for host selection. However, the effect of epicuticular wax of cabbage leaves on host selection by P. rapae remains unclear. This study was aimed to determine the effects of leaf epicuticular wax on female oviposition and larval feeding of P. rapae. We used a common cabbage variety 'Kinkei 201' containing n-nonacosane as the predominant leaf wax component. Wax removal treatments, in which the leaf surface was rubbed with cotton balls, significantly increased female oviposition and mid-stage (2nd-4th instars) larval feeding compared with untreated (intact) leaves. Spraying treatments with n-nonacosane standard on wax-removed leaves significantly suppressed female oviposition and mid-stage larval feeding. Thus, n-nonacosane in cabbage leaf epicuticular wax potentially affects host selection and preference by P. rapae. In contrast, final-stage (5th instar) larvae significantly preferred intact leaves to wax-removed leaves, and spraying treatments with n-nonacosane did not significantly change their feeding on wax-removed leaves. This suggests that young larvae are more susceptible to wax feeding inhibition than older larvae and that increasing leaf wax content enhances the resistance of cabbage against P. rapae. Acquiring these traits in cabbage leaves through improved breeding and cultivation methods may reduce and control the oviposition and feeding damage by P. rapae.