Journal of Chemical Ecology

Body odors inform human kin recognition. However, underlying chemical mechanisms and how they relate to body odor perception are still unclear. The present study therefore simultaneously examined perceptual body odor similarity according to human raters, its chemical basis and the link between the two in human families. The study included 33 raters who assessed body odors collected from 60 odor donors belonging to 15 biological families. Each family comprised a mother, a father and one adolescent same-sex sibling-dyad (8 sister dyads, 7 brother dyads). Body odor sampling was conducted with cotton pads for presentation to human raters and with thermal desorption (TD) tubes for Gas Chromatography-Mass Spectrometry (GC-MS) analysis. Relatedness and sex predicted perceived body odor similarity in parent-offspring versus unrelated control dyads. Analyses of chemical profiles revealed greater body odor similarity within families than between unrelated individuals. Parallel to the perceptual results, relatedness and sex predicted chemical similarity based on whole odor profiles. Finally, a machine-learning prediction model integrating perceptual and chemical data, revealed a small but significant positive association between chemical similarity of body odor and perceived olfactory similarity according to human raters, suggesting that odor perception is partly informed by chemical characteristics. Overall, the present study extends our understanding of human chemosensory communication and supports the notion of a family-specific olfactory signature.

When mating among genetically related individuals results in inbreeding depression, various behaviors and life-history traits evolve to favor outbreeding. Long-range sexual communication following natal dispersal is one such adaptation. In parasitoid wasps with single-locus complementary sex determination (sl-CSD), inbreeding increases the production of unviable or sterile diploid males. Mastrus ridens is such a species, with a genetic load underpinned by sl-CSD, combined with a high potential for sibmating because siblings emerge in close proximity from the same host and become sexually active shortly after emergence. With this context in mind, we investigated the mate-finding strategy of M. ridens using complementary behavioral, chemical, and electrophysiological approaches. Wind-tunnel bioassays and field experiments showed that males orient toward virgin females and, to a lesser extent, mated females. This attraction from a distance appeared to be the sole form of conspecific attraction. Chemical analyses using static and dynamic headspace sampling and solvent extracts, followed by GC-MS, revealed several potential pheromonal candidates, including methyl 6-methylsalicylate. This compound elicited reproducible antennal responses in males in GC-EAD recordings. Altogether, our results suggest that mate finding in M. ridens is guided by a volatile sex pheromone emitted by females, with methyl 6-methylsalicylate as one putative component. Such mate-finding mechanisms promote outbreeding and may explain the low proportion of unfit diploid males observed in natural populations. Surprisingly, chemical analyses suggested that males also emit this compound, whereas neither males nor females showed behavioral responses to males. This apparent discrepancy suggests that attraction may depend on a more complex pheromonal signal and opens further avenues for investigation.

Rising temperatures linked to global climate change can disrupt the chemical communication that animals rely on for reproduction. Arthropods are particularly vulnerable due to their limited ability for thermoregulation and their reliance on cuticular hydrocarbons (CHCs), which have a dual role in social communication and heat protection. Heat-induced changes in cuticular composition may therefore lead to mate recognition errors. We tested this in the burying beetle Nicrophorus vespilloides, by exposing males to either benign temperatures (20{degrees}C) or a simulated 3-day heatwave (26{degrees}C). We recorded the frequency of same-sex sexual behaviour under these contrasting thermal conditions and examined associated changes in the males' cuticular profiles. Our results show a higher rate of same-sex mounting under heat stress, with the CHCs of heat-stressed males shifting toward more saturated, longer-chained compounds and more female-like compounds. We also found a positive association between chain length and the frequency of same-sex mounting, suggesting a trade-off between the social communication and waterproofing functions of CHCs. Overall, our findings provide evidence for a causal effect of heat on same-sex sexual behaviour, which may be partly explained by changes in cuticular lipids. Such disruption of chemical communication could have major consequences for animal reproduction in a warming world.

1. Since plants interact with their environment through complex combinations of phytochemicals rather than metabolites in isolation, quantifying plant chemodiversity is of increasing interest. Although functionally relevant, structural disparity is mostly neglected in measures of chemodiversity because its integration relies on known compound identity, limiting broad application. 2. We established an approach deriving compound dissimilarity from UV-Vis spectra in HPLC-DAD datasets, evaluated how it relates to structure- or biosynthesis-based approaches, and examined whether it provides meaningful contributions to chemodiversity measures. For this, we applied it in an experiment full-factorially testing the effects of drought and herbivory on Solanum dulcamara leaf chemodiversity. 3. UV-Vis spectral dissimilarity aligned well with fMCS-based structural dissimilarity and reflected structural relationships within a set of standards. Incorporating it into chemodiversity analysis improved separation of the effects of drought and herbivory. Especially in the combination of both stresses, their distinct effects on different leaf metabolites were only fully reflected when accounting for compound disparity. 4. Hence, UV-Vis spectral dissimilarity captures chemically meaningful compound relatedness without requiring compound identity. Using it as a proxy for compound disparity adds a biologically relevant dimension to measures of chemodiversity with broader implications when assessing functional consequences of phytochemical diversity.

Volatile organic compounds (VOCs) define the distinctive aroma of cannabis and critically influence consumer preference, cultivar authentication, and breeding programs. However, systematic characterization of VOC diversity across commercial drug-type cultivars remains limited. This study presents a comprehensive volatilomics-based phenotypic characterization of 165 commercial drug-type cannabis accessions using gas chromatography with flame ionization detection and mass spectrometry (GC-FID/MS). We identified 61 high-confidence VOCs assigned to three biosynthetic classes: terpenoids (n = 45), fatty acid-derived volatiles (n = 12) and amino acid-derived volatiles (n = 4), resolved into 12 subclasses. Analysis of variance revealed highly significant among-accession differences for all compounds (p < 0.001; 2 = 0.67-0.97), with repeatability estimates averaging 0.81 (range 0.50-0.95). Unsupervised clustering partitioned accessions into three distinct chemotypes (n = 90, 53, and 22), supported by principal component and t-SNE analyses. Machine learning-based feature selection identified a consensus panel of 12 discriminative compounds (camphene, -fenchene, sabinene, -terpinene, ({+/-})-limonene, -humulene, linalool, endo-fenchol, {Delta}3-carene, -thujene, {gamma}-terpinene and -phellandrene) that recovered the chemotype assignment of 32 of 33 held-out accessions. Estimated odor-activity screening ranked prenylthiol, -pinene, ({+/-})-limonene, linalool and myrcene highest among the odor-active compounds. All three chemotypes shared a prenylthiol-dominated core (67-77% of summed OAV) and were distinguished by the extent and nature of terpenoid modulation of that core: minimally modulated (Cluster ZERO), citrus-floral modulated (Cluster ONE) and pine-terpenic modulated (Cluster TWO). These findings indicate that volatile diversity in this panel can be summarized by three reproducible chemotypes, providing a quantitative basis for accession characterization and a foundation for future breeding and quality-assessment studies.

Ethanol is naturally present in nectar, but we still know little about how pollinators cope with long-term exposure to it at low concentrations. We exposed adult worker honeybees (Apis mellifera carnica Poll.) for eight days to diets containing 0, 0.1, 0.5, 1, 2, or 10% ethanol and measured survival, estimated intake, open-field locomotion, sting extension, whole-body trehalose, and hemolymph ethanol. Hemolymph ethanol was correlated with dietary concentration, attesting to internal exposure. Survival differed among diets, an effect which was driven by the difference between the 10% ethanol treatment and the control. Food intake was lowest at the 10% ethanol diet. There was also a modest increase in intake under the 0.1% ethanol treatment. In terms of locomotor features, bees moved less, moved more slowly, explored less space, covered shorter distances, and followed more tortuous paths after the 10% ethanol treatment. Neither sting extension nor trehalose were affected by dietary ethanol. The results showed no beneficial stimulation at lower concentrations. Instead, performance was endpoint-specific: at 0.1-2% ethanol in the diet, performance remained relatively stable across most parameters, whilst clear impairment was evident at 10%. These findings highlight resilience to repeated ethanol exposure in honeybees.

The generalist Helicoverpa armigera and the specialist Helicoverpa assulta are closely related noctuid pests and are among the few insect herbivores capable of feeding on and damaging hot pepper fruits, which contain the defensive compound capsaicin. Cytochrome P450 monooxygenases (P450s) contribute to the metabolism of plant defensive compounds and can facilitate insect adaptation to chemically defended host plants. Here, we identified CYP6AN1 in H. assulta (HassCYP6AN1) and comparatively characterized the CYP6AN1 orthologs from H. armigera (HarmCYP6AN1) and H. assulta. RACE identified one full-length HarmCYP6AN1 transcript and three full-length HassCYP6AN1 transcript isoforms. The HassCYP6AN1 isoforms contained distinct 5' UTRs generated by alternative transcription initiation and splicing but shared an identical coding sequence. Sequence comparisons and phylogenetic analysis supported their assignment as orthologs. Constitutive CYP6AN1 expression was higher in the H. assulta midgut, whereas dietary capsaicin significantly induced CYP6AN1 expression in the H. armigera midgut. Recombinant CYP6AN1 proteins were co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli, and their substrate-metabolizing activities were evaluated using HPLC-based depletion assays. Both orthologs metabolized capsaicin, but HarmCYP6AN1 exhibited an approximately 2.3-fold higher depletion activity than HassCYP6AN1 under the conditions tested. HarmCYP6AN1 also showed P450-content-dependent xanthotoxin depletion, whereas no detectable xanthotoxin metabolism was observed for HassCYP6AN1. These findings establish CYP6AN1 as a component of the capsaicin-metabolizing repertoire of both species and reveal substantial divergence between the orthologs in transcript organization, expression regulation, catalytic activity, and detectable substrate range.

Here, oyster larval developmental abnormalities within a New England hatchery were linked to a common UV sterilization technique that has been used for over 20 years. Because of the known link between phytoplankton oxylipins and egg mortality in copepods, we hypothesized that UV pretreatment of seawater results in the production of oxylipins that inhibit larval digestion of microalgae. We used lipidomics to observe changes in the organic compounds dissolved in estuarine seawater when filtered and when filtered and pretreated with UV. UV treatment resulted in an increase in the relative abundance of oxylipins associated with cyanobacteria, fungi, and macroalgae in 2020, whereas oxylipins typically produced by diatoms were more abundant in the UV treatments from 2021. Oxylipin concentrations were higher in 2020, when the hatchery reported the most severe problems with larval development. Removing the UV step allowed continued larval production in both years. However, the lack of UV sterilization led to an unidentified bacterial pathogen in 2021, which nearly decimated the overall seasonal production of oyster seed. To follow up in a more controlled environment, the larvae were exposed to exogenous oxidized lipids, which resulted in the same digestive syndrome and histological symptoms as the endogenous suite of compounds produced by UV. Further investigation of the lipidomes revealed that oxylipins were only one class of potentially harmful compounds linked to UV sterilization, and the dissolved concentrations of secondary metabolites associated with higher plants, a wide range of pharmaceuticals, and anthropogenic organic pollutants also increased under UV light. Future efforts will explore the sources of these compounds, the mechanisms by which they inhibit oysters, and whether this is an emerging environmental problem for other ecosystems and shellfish hatcheries. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/738347v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@43d06corg.highwire.dtl.DTLVardef@2894daorg.highwire.dtl.DTLVardef@449e59org.highwire.dtl.DTLVardef@f81983_HPS_FORMAT_FIGEXP M_FIG C_FIG

Characterizing the enzymatic accommodation of circular agricultural fertilizers is critical for informing strategies to remediate widespread soil sulfur hunger. Here, we present an exploratory in-silico investigation evaluating the active-site cleft of sulfate thiohydrolase (SoxB) across representative soil Proteobacteria. Following the crystallographic precedent of uncomplexed thiosulfate in PDB 2WDE, site-directed molecular docking indicated that the free thiosulfate polyanion binds favorably within the catalytic pocket (predicted affinity: -3.506 kcal/mol), yielding a substantially lower empirical energy barrier than hydrophobic elemental sulfur (S8, -1.409 kcal/mol). Comparative evaluation against the alkaline-adapted Thiobacillus denitrificans homolog revealed an elevated predicted binding affinity of -4.610 kcal/mol, suggesting a potential structural accommodation in high-pH calcareous soils (pH > 8.0). Unrestrained 5.0 ns all-atom molecular dynamics in explicit TIP3P solvent demonstrated initial structural stability of the unliganded host backbone (RMSD = 1.10 +/- 0.15 Angstrom). Energetic decomposition indicated that ligand association is governed predominantly by electrostatic interactions (delta-E_elec ~ -40 kcal/mol) with basic residues (His146, His269, Trp147; RMSF < 0.60 Angstrom), with a single-trajectory unbinding event observed at 3.2 ns. These computational observations provide an exploratory baseline characterizing the active-site electrostatic landscape of SoxB, generating working hypotheses for downstream empirical soil microcosm and in-planta trials.

Urban green infrastructure is increasingly promoted as a public-health intervention, yet the biological features that determine exposure to potentially beneficial plant-derived volatile compounds remain poorly understood. Here we quantified airborne terpenes and terpenoids across five contrasting urban greenspaces in Oxford, UK, and related chemical profiles to plant diversity, vegetation structure and surrounding habitat characteristics. Ambient air samples collected across spring and summer were analysed by thermal-desorption gas chromatography-mass spectrometry, alongside field surveys of taxonomic richness, canopy cover, vegetation volume and ground composition. Terpene and terpenoid scentscapes differed strongly among sites and through time, with monoterpenes dominating detected profiles. Sites with greater plant richness and greater vegetation volume below 1.5 m consistently showed higher terpene/terpenoid abundance, whereas total vegetation volume, canopy cover and tree abundance were weaker and less consistent predictors. These relationships were specific to plant-associated chemical classes and were not observed for predominantly anthropogenic volatile compounds. These patterns were resolved across only five independent sampling sites, and the relationships reported here should therefore be considered exploratory. Our findings suggest that human exposure to plant-derived volatiles in cities may be maximised not simply by increasing tree cover, but by designing biodiverse, structurally complex lower-to-mid-storey vegetation within the breathing zone. These results provide an empirical basis for incorporating scentscape ecology into health-oriented urban greenspace design.

Tropospheric ozone (O) is a major atmospheric pollutant that affects plant carbon metabolism, redox homeostasis, and secondary metabolism, including the biosynthesis and emission of biogenic volatile organic compounds (BVOCs). However, the contribution of BVOCs to O3 tolerance, particularly in tropical woody species, remains poorly understood. Here, we investigated whether acute O exposure (cumulative AOT40 of 3497.82 ppb h) induces alterations in photosynthetic performance, redox homeostasis, and BVOC partitioning in Eugenia uniflora. We evaluated gas exchange, photosynthetic pigments, ascorbate and glutathione pools, emitted BVOCs, modeled intercellular BVOC concentrations, and the relative carbon cost associated with BVOC emissions. O exposure significantly increased net CO2 assimilation without affecting stomatal conductance, transpiration, leaf water status, or chlorophyll concentrations, indicating maintenance of photosynthetic performance. Carotenoid concentrations and total glutathione decreased, whereas glutathione redox status was maintained. O induced marked compound-specific changes in BVOC composition and partitioning. Several monoterpenes appeared exclusively under O exposure, {gamma}-elemene emission increased significantly, and the relative distribution of individual BVOCs between the modeled intercellular and emitted pools was altered. These findings show that the response of E. uniflora to acute O exposure was characterized by interplay among carbon assimilation, glutathione redox regulation, and BVOC partitioning rather than by increased total volatile emission. Enhanced carbon assimilation occurred without additional carbon loss through BVOC release, while changes in the modeled intercellular pool indicate that part of the volatile response remained within the leaf. Our findings highlight BVOC partitioning as an important dimension of the plant response to oxidative stress and demonstrate that emission measurements alone may not fully capture the fate and potential physiological role of volatile carbon under O exposure. O_FIG O_LINKSMALLFIG WIDTH=178 HEIGHT=200 SRC="FIGDIR/small/743946v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@653af1org.highwire.dtl.DTLVardef@ca5forg.highwire.dtl.DTLVardef@1e641bforg.highwire.dtl.DTLVardef@1e68fae_HPS_FORMAT_FIGEXP M_FIG C_FIG BVOC Partitioning Contributes to Oxidative Stress Defence Under Acute O Exposure

To elucidate the resistance of hybrid larch (Larix spp.) clones to Dendrolimus superans and their chemical defense mechanisms, 46 clones were subjected to field feeding-infestation experiments. Insect resistance was comprehensively evaluated by the membership function method from three perspectives: insect weight change, frass weight and defoliation rate (damage consequences); pre- and post-infestation physiological indices (constitutive and induced resistance). High- and low-resistance materials screened from each perspective were further analyzed by widely targeted LC-MS metabolomics. The three damage indices differed highly significantly among clones (P<0.01) and were positively correlated, indicating abundant genetic variation in resistance. Clones such as -30-C, -35-A and -21-A showed strong overall resistance, whereas -28-E and -20-A showed high constitutive and induced resistance. Defence enzyme activities (POD, SOD, CAT, PPO and PAL) correlated closely with secondary metabolites (total phenolics, tannins and total flavonoids) and nutrients, and rose synergistically after feeding, reflecting synergy between constitutive and induced resistance. In total, 3,577 metabolites were identified, predominantly terpenoids (>90%). The three groups yielded 1,010, 1,086 and 922 differentially accumulated metabolites, and PCA separated high- from low-resistance materials in all groups. These metabolites were significantly enriched in metabolic pathways, biosynthesis of secondary metabolites, monoterpenoid and diterpenoid biosynthesis, and phenylpropanoid biosynthesis. In conclusion, resistance of hybrid larch to D. superans is jointly conferred by the defence enzyme system, secondary metabolite accumulation and a 'terpenoid-phenolic' metabolic network: terpenoids and phenolics act synergistically via the terpenoid and phenylpropanoid pathways, together forming the core of chemical defense and supporting the breeding of insect-resistant clones.

Barley yellow dwarf virus (BYDV), transmitted by the bird cherry-oat aphid (Rhopalosiphum padi L.), is among the most damaging viral diseases of barley, but the mechanisms underlying resistance to both the virus and its vector remain poorly understood. Here, we investigated resistance associated with the Hordeum bulbosum-derived Ryd4 introgression in the barley hybrid SY Kestrel by integrating behavioural, electrophysiological, physiological and multi-omics analyses with functional validation of defence metabolites. SY Kestrel exhibited constitutive volatile-mediated antixenosis together with strong post-settlement antibiosis characterised by impaired phloem feeding, reduced aphid fitness and suppression of BYDV gene expression 10 days after transmission. Integrated transcriptomic, metabolomic and small RNA analyses revealed coordinated immune activation, chloroplast remodelling and defence metabolism associated with the resistance introgression. Candidate immune regulators were identified both within the refined Ryd4 interval and the surrounding introgressed region. Maintenance of photosystem II function was accompanied by reprogramming of -linolenic acid-derived oxylipin metabolism, while phenylpropanoid and branched-chain amino acid/lysine pathways generated metabolites that directly reduced aphid survival. We demonstrate that the Ryd4 introgression coordinates constitutive vector deterrence with host defence reprogramming to restrict aphid colonisation and suppress BYDV establishment. These results provide a mechanistic framework for improving durable resistance to aphid-transmitted viruses in cereals.

Nectar is a primary floral reward, which can also deter non-specialist pollinators; yet, the role of complex nectar composition in plant-pollinator interactions and its relationship to other floral traits remain understudied, particularly in natural communities. We profiled the nectar metabolome of 43 co-occurring species in an alpine grassland to evaluate relationships among nectar chemistry, phylogeny, floral display traits and pollinator visitation. Field observations revealed a dominant bee vs fly visitation gradient. Several aggregated nectar traits tracked this gradient independently of plant phylogeny, indicating functional convergence: specifically, bee visitation was associated with higher nectar sucrose proportion, greater compound richness, and more divergent profiles of uncommon sugars. Nectar traits exhibited variable relationships to floral display traits, suggesting partial inter-trait phenotypic integration. Together, these findings indicate that detailed features of nectar composition, including phytochemical diversity, play a functional role in floral phenotypes, with previously unappreciated implications for plant-pollinator community ecology.

Ethanol occurs naturally in sugar-rich foods used by insects, but its effects in bees have been studied primarily in honeybees. We tested whether dietary ethanol affects survival and locomotor performance in workers of the bumblebee Bombus terrestris (L.). In the survival experiment, workers were fed ethanol (0, 1, or 10%) for 21 days; in the locomotor experiment, they were fed the same doses for one or seven days, after which we measured spontaneous movement using an open-field assay. We measured the proportion of time in movement, speed of movement, path meander (curviness), and arena exploration. The 10% ethanol concentration greatly increased the risk of mortality, whereas the estimated effect of 1% ethanol was smaller and statistically inconclusive. In terms of locomotion, the largest differences occurred after seven days of exposure to 10% ethanol. Workers in this treatment showed greater path meander and lower exploration than control workers. Speed was also lowest in this group. Evidence that exposure for seven days was worse than for one day at the same concentration was detected only for exploration. No clear locomotor effect was detected at 1% ethanol exposure. These findings provide comparative data on sustained ethanol exposure in bumblebees and show a strong concentration-dependent contrast, with substantial effects under high-concentration challenge but no clear effects on the measured endpoints at 1%.

Odors allow animals to evaluate resources and risks, but the neural and inherited consequences of experience with ecologically meaningful odors remain poorly understood. Since both parasitoids and entomopathogenic fungi are widely used as agents in integrated biocontrol, we asked whether exposure to pathogen-associated volatiles can reassign odor value in a parasitoid wasp and whether the acquired bias is transmitted to descendants. Adult female Scleroderma guani were exposed, without host contact, to volatiles from Beauveria bassiana-infected hosts or to methyl cinnamate (MC), a representative component of the infected-host odor. Twelve-hour exposure shifted subsequent choices away from infected-host odor and MC, whereas shorter exposure produced different effects, indicating duration-dependent olfactory plasticity. The shift occurred without an explicit reward or punishment and is therefore consistent with non-associative learning. Unexposed F1 and F2 descendants of MC-exposed females expressed the same avoidance bias. MC stimulation elicited stronger calcium responses in mushroom-body regions of trained females and their descendants. Head transcriptomes identified reduced expression of the crustacean cardioactive peptide receptor (CCAPR) as a shared molecular signature, and CCAPR RNA interference phenocopied the odor-avoidance behavior. Finally, maternal treatment with sinefungin, a broad S-adenosylmethionine-dependent methyltransferase inhibitor, left maternal behavioral shift intact but abolished the F1 bias, implicating a methylation-sensitive process in transmission. Together, these results reveal that a pathogen-associated odor can induce durable, cross-generational reweighting of olfactory value in a non-model insect and identify candidate neural and neuropeptidergic mechanisms linking sensory experience to inherited behavior, and providing a new perspective on utilizing training in integrated biocontrol as well.

Nutrition plays a fundamental role in insect physiology, yet whether growth, immunity and stress responses share a common nutritional optimum remains poorly understood. Using the Geometric Framework for Nutrition, we investigated how dietary protein and carbohydrate balance regulate multiple physiological functions in the specialist herbivore Plutella xylostella. Growth was jointly determined by protein and carbohydrate intake, with maximal biomass accumulation constrained primarily by protein availability. Immune traits showed distinct nutritional optima: total hemocyte counts and phenoloxidase activity were maximised at intermediate protein-carbohydrate (P:C) ratios, whereas survival following Bacillus thuringiensis challenge depended predominantly on protein intake. Antioxidant and detoxification responses likewise varied non-linearly across the nutrient landscape, with individual enzyme systems each exhibiting distinct nutrient-dependent optima. Importantly, no single macronutrient balance simultaneously maximised growth, immune performance and oxidative homeostasis, demonstrating that these functions have divergent nutritional requirements. Together, these findings show that macronutrient balance generates competing physiological demands, offering an integrated view of nutrient-dependent regulation of growth, immunity and stress physiology in a specialist herbivore.

The human gut is home to more than 100 trillion bacteria, where various environmental factors, such as nutrients and gases, exist and influence them. The levels of fermentation gases in the gut, including CO2, fluctuate depending on the host's diet. However, how CO2, an environmental factor, affects the physiological states of gut anaerobes remains poorly understood, but CO2 is often utilized in their cultivation. Akkermansia muciniphila (A. muciniphila) is widely studied as a beneficial human gut microbe. However, the effects of CO2 on the physiological state of A. muciniphila are not fully understood. In this study, we focused on CO2 as an environmental factor and aimed to clarify how CO2 affects the physiological state of A. muciniphila. Culture experiments showed that compared with the absence of CO2, the presence of CO2 significantly increased the growth of A. muciniphila. The results of the metabolomic analysis revealed distinct metabolic profiles in the presence or absence of CO2. The tracing analysis using stable 13C-labelled CO2 demonstrated that CO2 was incorporated into various metabolites in the TCA cycle, the de novo purine/pyrimidine synthesis pathways, and other pathways. In addition, the activity of pyruvate carboxylase, which catalyses an anaplerotic reaction involving CO2 fixation to supply oxaloacetate (OAA) to the TCA cycle, was significantly higher in A. muciniphila cells grown in the presence of CO2. Moreover, supplementation with OAA increased the growth of A. muciniphila in a dose-dependent manner, mirroring the effects of CO2 supplementation. These findings suggest that A. muciniphila utilizes CO2 for an anaplerotic reaction in the TCA cycle and other pathways involving CO2 incorporation, facilitating metabolic flux to promote its robust growth.

Males can influence future mating interactions of females after copulation by changing female signals that subsequent males will encounter. In insects, such effects commonly involve cuticular hydrocarbons (CHCs), but whether heritable microbial symbionts contribute to post-mating chemical signalling remains largely unknown. Kelly's citrus thrips, Pezothrips kellyanus, provides an ideal system to address this question because reproductive compatibility is shaped by common arthropod endosymbionts. Across P. kellyanus populations, Cardinium occurs in almost all individuals whereas Wolbachia varies in prevalence and appears to spread by cytoplasmic incompatibility (CI). Yet, females with only Cardinium (C) avoid incompatible males carrying both Cardinium and Wolbachia (CW), and this discrimination is linked to the distinct CHC profile of CW males. Here, we tested whether this endosymbiont-associated male perfume persists on females beyond copulation by altering the female CHC profile and subsequent male mating behaviour. Using behavioural assays and GC-MS-based CHC profiling, we found that, independent of female endosymbiont association, females first mated with CW males received fewer antennal contacts and mating attempts from subsequent C males. Furthermore, mating remodelled female CHC profiles, while mating with CW males produced a distinctive post-mating chemical signature. Most notably, tridecane, previously detected only in CW males, occurred exclusively in females mated with CW males. Our findings show that endosymbionts can alter mated female CHCs and influence future sexual communication between male and female hosts. These findings reveal a previously unrecognised post-mating route through which endosymbionts reshape sexual communication, with potential consequences for reproductive compatibility and symbiont transmission dynamics.

Cannabis is well known for its pungent, skunk-like aroma. Recent chemical studies have identified prenylated and C6 volatile sulfur compounds as contributors to its skunky and citrus-like aromas, but the pathways that produce these compounds remain unknown. This gap limits efforts to explain variation in sulfur-aroma traits and to selectively enhance or reduce those traits. To address this gap, we used the known chemistry of sulfur-containing volatiles in Cannabis and characterized sulfur and volatile biosynthetic pathways in other plant species to select candidate enzyme groups. Because the GMO cultivar is anecdotally associated with a pronounced sulfurous aroma, reference protein sequences and profile hidden Markov models were used to search its version 1 (v1) primary high-confidence protein set of 55,790 sequences. These searches recovered 975 unique proteins. Sequence screening retained 941 candidates across 20 reporting categories; 939 contained all expected domains, while the two candidates assigned to the methionine gamma-lyase (MGL)-nearest category had no category-specific expected-domain rule. The largest reporting category comprised 359 proteins containing a cytochrome P450 domain, recovered through a search motivated by cytochrome P450 family 74 (CYP74) enzymes involved in oxylipin and plant volatile formation. Thirteen of these proteins were also recovered by at least one full-length CYP74 reference search. Other large reporting categories included 218 sugar-transferase, 83 glutathione-transferase, and 61 alcohol dehydrogenase candidates. Comparison with the Cannabis Expression Atlas linked 168 candidates to 128 annotated genes through 100%-identity amino-acid matches spanning at least 80% of each GMO v1 candidate protein. Twenty-nine genes were tissue-specific, including 13 root-specific and 6 trichome-specific genes. These results define candidates for biochemical testing and direct searches for additional enzymes acting upstream and downstream in Cannabis sulfur-volatile pathways.