Plant-derived Odorants Research Articles

Functional characterization of four antenna-biased chemosensory proteins in Dioryctria abietella reveals a broadly tuned olfactory DabiCSP1 and its key residues in ligand-binding

The orientation of the oligophagous cone-feeding moth Dioryctria abietella (Lepidoptera: Pyralidae) to host plants primarily relies on olfactory-related proteins, particularly those candidates highly expressed in antennae. Here, through a combination of expression profile, ligand-binding assay, molecular docking and site-directed mutagenesis strategies, we characterized the chemosensory protein (CSP) gene family in D. abietella. Quantitative real-time PCR (qPCR) analyses revealed the detectable expression of all 22 DabiCSPs in the antennae, of which seven genes were significantly enriched in this tissue. In addition, the majority of the genes (19/22 relatives) had the expression in at least one reproductive tissue. In the interactions of four antenna-dominant DabiCSPs and different chemical classes, DabiCSP1 was broadly tuned to 27 plant-derived odors, three man-made insecticides and one herbicide with high affinities (Ki < 6.60 μM). By contrast, three other DabiCSPs (DabiCSP4, CSP6 and CSP17) exhibited a narrow odor binding spectrum, in response to six compounds for each protein. Our mutation analyses combined with molecular docking simulations and binding assays further identified four key residues (Tyr25, Thr26, Ile65 and Val69) in the interactions of DabiCSP1 and ligands, of which binding abilities of this protein to 12, 15, 16 and three compounds were significantly decreased compared to the wildtype protein, respectively. Our study reveals different odor binding spectra of four DabiCSPs enriched in antennae and identifies key residues responsible for the binding of DabiCSP1 and potentially active compounds for the control of this pest.

Two Antenna-Enriched Odorant Binding Proteins in Dioryctria abietella Tuned to General Odorants and Insecticides

The management of forest pests has become a significant challenge, particularly for wood borers, because they spend most of the time in the trunks or cones. The coneworm, Dioryctria abietella, is a representative of cone borers as its larvae feed on the cones of Pinaceae plants. The molecular mechanisms underlying the interactions between this species and host plants or habitats can assist in developing strategies for pest control. In this study, we extended the expression profiles of 32 odorant binding proteins (OBPs) in the reproductive tissues of D. abietella, revealing the detectable transcription of 29 genes. Using two DabiOBPs highly expressed in antennae (DabiOBP5 and DabiOBP14) as targets, six compounds with high affinities (dissociation constants < 13 μM) were identified through a reverse chemical ecology strategy, including insecticides widely used for the control of lepidopteran pests. Of these compounds, a floral volatile β-ionone and a pear-produced ester ethyl-(2E,4Z)-decadienoate may serve as behaviorally active compounds in D. abietella. The strong binding of DabiOBPs to insecticides suggested their involvement in insecticide resistance, reflecting sophisticated detoxification mechanisms of this moth. In the molecular simulations, DabiOBP14 possessed stronger interactions with the six ligands compared to DabiOBP5, in which a few key residues within the binding pockets were involved in the formation of hydrogen bonds. This study provides some valuable reference active compounds for the development of lures or repellents in D. abietella and unravels the putative roles of two antenna-dominant DabiOBPs in the perception of plant-derived odorants and insecticides.

Norepinephrine and dopamine contribute to distinct repetitive behaviors induced by novel odorant stress in male and female mice

Exposure to unfamiliar odorants induces an array of repetitive defensive and non-defensive behaviors in rodents which likely reflect adaptive stress responses to the uncertain valence of novel stimuli. Mice genetically deficient for dopamine β-hydroxylase (Dbh−/−) lack the enzyme required to convert dopamine (DA) into norepinephrine (NE), resulting in globally undetectable NE and supranormal DA levels. Because catecholamines modulate novelty detection and reactivity, we investigated the effects of novel plant-derived odorants on repetitive behaviors in Dbh−/− mice and Dbh+/− littermate controls, which have catecholamine levels comparable to wild-type mice. Unlike Dbh+/− controls, which exhibited vigorous digging in response to novel odorants, Dbh−/− mice displayed excessive grooming. Drugs that block NE synthesis or neurotransmission suppressed odorant-induced digging in Dbh+/− mice, while a DA receptor antagonist attenuated grooming in Dbh−/− mice. The testing paradigm elicited high circulating levels of corticosterone regardless of Dbh genotype, indicating that NE is dispensable for this systemic stress response. Odorant exposure increased NE and DA abundance in the prefrontal cortex (PFC) of Dbh+/− mice, while Dbh−/− animals lacked NE and had elevated PFC DA levels that were unaffected by novel smells. Together, these findings suggest that novel odorant-induced increases in central NE tone contribute to repetitive digging and reflect psychological stress, while central DA signaling contributes to repetitive grooming. Further, we have established a simple method for repeated assessment of stress-induced repetitive behaviors in mice, which may be relevant for modeling neuropsychiatric disorders like Tourette syndrome or obsessive-compulsive disorder that are characterized by stress-induced exacerbation of compulsive symptoms.

Supplementing Blood Diet With Plant Nectar Enhances Egg Fertility in Stomoxys calcitrans.

Stomoxys calcitrans (stable fly) is a cosmopolitan biting fly of both medical and veterinary importance. Unlike blood-feeding-related behavior of stable fly, its plant feeding, the fitness value, and the S. calcitrans–plant interaction are less understood. Here we show based on two chloroplast DNA genes, ribulose bisphosphate carboxylase large chain (rbcL) and the intergenic spacer gene trnH-psbA, that field-collected male and female stable flies fed on various plant species. We investigated the fitness cost of plant feeding using Parthenium hysterophorus, one of the plant species identified to have been fed on by the field-collected flies. Supplementation of blood feeding with a flowering P. hysterophorus plant as nectar source enhanced egg hatchability significantly as compared to blood alone, showing the fitness value of nectar supplementation. However, nectar supplementation did not affect the number of eggs laid or longevity of S. calcitrans as compared to flies that fed on blood alone. S. calcitrans maintained on sugar alone failed to lay eggs. The various plants stable flies fed on demonstrated chemodiversity with their own signature scent. The behavioral response of S. calcitrans to these signature compounds varied from strong attraction (γ-terpinene) to neutral (linalool oxide and myrcene) to repellency (butanoic acid). Our study demonstrated that stable flies feed on nectar, and plant nectar supplementation of blood feeding enhanced larval emergence. Thus, our result has implication in stable fly reproduction, survival, disease transmission, boosting laboratory colony, and the possibility of using plant-derived odors for mass trapping of stable fly, for instance, using γ-terpinene.

Two carboxylesterase genes in Plutella xylostella associated with sex pheromones and plant volatiles degradation.

Carboxyl/cholinesterases (CCEs) are thought to play a pivotal role in the degradation of sex pheromones and plant-derived odorants in insects, but their exact biochemistry and physiological functions remain unclear. In this study, two paralogous antennae-enriched CCEs from Plutella xylostella (PxylCCE16a and 16c) were identified and functionally characterized. High-purity protein preparations of active recombinant PxylCCE16a and 16c have been obtained from Sf9 insect cells by Ni2+ affinity purification. Our results revealed that the purified recombinant PxylCCE016c is able to degrade two sex pheromone components Z9-14:Ac and Z11-16:Ac at 27.64 ± 0.79% and 24.40 ± 3.07%, respectively, while PxylCCE016a presented relatively lower activity. Additionally, a similar difference in activity was measured in plant-derived odorants. Furthermore, both CCEs displayed obvious preferences for the two sex pheromone components, especially on Z11-16:Ac (Km values are in the range 7.82-45.06 μmol L-1 ) which much lower than plant odorants (Km values are in the range 1290-4030 μmol L-1 ). Furthermore, the activity of the two newly identified CCEs is pH-dependent. The activity at pH6.5 is obviously higher than that at pH5.0. Interestingly, only PxylCCE016c can be inhibited by a common esterase inhibitor triphenyl phosphate (TPP) with LC50 of 1570 ± 520 μmol L-1 . PxylCCE16c plays a more essential role in odorant degradation than PxylCCE16a. Moreover, the current study provides novel potential pesticide targets for the notorious moth Plutella xylostella. © 2021 Society of Chemical Industry.

A candidate aldehyde oxidase in the antennae of the diamondback moth, Plutella xylostella (L.), is potentially involved in the degradation of pheromones, plant-derived volatiles and the detoxification of xenobiotics

Insect antennae play a fundamental role in perceiving and recognizing a broad spectrum of conventional semiochemicals and host plant-derived odors. As such, genes that are tightly associated with the antennae are thought to have olfactory-related roles related to signal transduction mechanisms. Several mechanisms suggest that enzymatic inactivation could contribute to the signal termination process, such as odorant-degrading enzymes (ODEs). To date, a few ODEs have been identified and characterized in detail in insect herbivores, but little is known about aldehyde oxidases (AOXs); moreover, direct in vivo experimental evidence is needed. AOXs are a major family of metabolic enzymes that oxidize a variety of aromatic aldehydes, and they may also play a significant role in detoxification and degradation of environmental chemical cues. Here, we report on the identification and characterization of a novel cDNA encoding the putative odorant-degrading enzyme, PxylAOX3, from the antennae of the diamondback moth, (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae). The purified recombinant protein showed a wide-range of substrate zymography oxidizing both sex pheromone compounds as well as plant-derived aldehydes with distinct activities. Our data suggest PxylAOX3 might be involved in the degradation of many structurally diverse aldehyde odorants. Furthermore, PxylAOX3 could participate in olfactory neuron protection by inactivation of redundant odorants and xenobiotic detoxification, making it a potential target for pesticide development as well.

Expression of various odorant-response defective (odr) genes in the entomopathogenic nematode Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae)

Entomopathogenic nematodes (EPNs) exhibit complex host-seeking behaviour in soil and utilise the insect- and plant-derived odorants to locate and infect their insect hosts. The odorant response defective (odr) genes were identified in Caenorhabditis elegans through a forward genetic screen for worms defective in odour sensing. It is hypothesised that odr genes could be involved in insect host recognition by the EPNs, but no information is available on these genes or their functions in EPNs. Here, we investigated and characterised odr genes in the EPN Heterorhabditis bacteriophora. Seven orthologs of C. elegans odr genes were identified by in-silico analysis in H. bacteriophora, of which four genes (Hb-odr-2, Hb-odr-3, Hb-odr-4 and Hb-odr-10) could be amplified and cloned from the cDNA. The developmental stage-specific expression in infective juvenile (IJ), fourth stage juvenile (J4) and adult stage of H. bacteriophora showed that Hb-odr-2, Hb-odr-3 and Hb-odr-10 were up-regulated only at the IJ stage, whereas Hb-odr-10 was significantly up-regulated in all the developmental stages. Exposure to insect hemolymph resulted in high transcript accumulation of Hb-odr-3 but did not affect the expression of other Hb-odr genes. The in-situ hybridisation assays showed that Hb-odr-2 mRNA expression was localised at the region of the nerve ring while that of Hb-odr-3 in the region of pharyngointestinal valve and anterior esophagous of the IJs. Our results extend the knowledge of C. elegans odr genes to the entomopathogenic nematode H. bacteriophora. To the best of our information, this is the second investigation on the characterisation of odr genes in a parasitic nematode after the plant-parasitic species Meloidogyne incognita.

Analyses of chemosensory genes provide insight into the evolution of behavioral differences to phytochemicals in Bactrocera species

Insect olfactory systems have evolved to recognize phytochemicals and respond to olfactory-triggered cues that vary depending on needs. Several Bactrocera species are attracted explicitly to particular phytochemicals, including methyl eugenol (ME) and cue lure/raspberry ketone (CL/RK). The attraction of Bactrocerans to ME/RK is primarily driven by olfaction. Therefore, the divergent behavioral phenotypes are due to the differences in genes expressed in antennae. High quality transcriptomes were generated with mRNA from dissected antennae, to analyze the differences in olfaction-related genes of three ME-responders B. dorsalis, B. papayae and B. correcta and two RK-responders B. cucurbitae and B. tau. Many distinct quantitative and qualitative differences were identified in their respective chemosensory repertoires. Tissue- and sex-specific expression analyses identified antennae-predominant and sex-biased chemosensory genes. Sequence comparison revealed variations among family members of odorant-binding proteins and odorant-receptors between ME-responders and RK-responders. Differences in composition, expression levels, and sequence of proteins encoded by olfactory-related genes were identified between ME-responders and RK-responders. Some of the differences might contribute to the divergence in response to plant-derived odorants. Taken together, our results provide insights into the evolution of an olfactory system at molecular level in Bactrocera ME- and CL/RK-responding species.

Morphological Aspects of Antennal Sensilla of the Rhodnius brethesi Matta, 1919 (Hemiptera: Reduviidae) from the Negro River, Amazon Region of Brazil.

Studies conducted in river Ererê located in the left margin of Negro River, municipality of Barcelos, state of Amazonas, have confirmed that Rhodnius brethesi has as its natural habitat the palm tree Leopoldinia piassaba. By scanning electron microscopy, sensillum type was studied on the antennae of R. brethesi. The specimens used come from the field and laboratory colony. No differences were observed between R. brethesi and other Triatominae studied. In the R. brethesi antennas, differences were observed only between the antennal segments and in the dorsal and ventral portions. Trichobothria sensilla show a difference with a lamellar base, suggesting that this conformation of the base of the sensilla is a synapomorphic feature of the genus. Another important observation is that, considering that R. brethesi is a specialist, infesting only one type of palm tree, trichoidea sensilla may be involved with plant-derived odorants. The knowledge of such functions could benefit the understanding of the likely biological role of these structures in chemical communication and also provide basic information for future studies of niche recognition, since this species of triatomine is only found in the L. piassaba palm.

A combination of plant-derived odors reduces corticosterone and oxidative indicators of stress.

In this study, we measured typical stress markers in addition to oxidative status and reduced glutathione in erythrocytes, and plasma lipid peroxidation of restraint-stressed animals exposed to a combination of plant-derived odors (0.03% Z-3-hexen-1-ol, 0.03% E-2-hexenal, and 0.015% α-pinene in triethyl citrate). Male Wistar rats aged 6-7 weeks postnatal were exposed to vehicle (triethyl citrate, n = 12), plant-derived odors (n = 12), or 1% propionic acid odor (n = 12) under control or stress conditions, and blood samples were collected. Restraint stress increased plasma glucose and plasma corticosterone concentrations by approximately 10% (P < 0.01) and 125% (P < 0.001), respectively, in vehicle-exposed animals. Similar increases were observed in animals exposed to a 1% propionic acid odor, indicating the novelty of odor exposure does not alter stress responsiveness. There was also an increase of approximately 15% in both erythrocytic oxidative status (P < 0.001) and plasma lipid peroxidation (P < 0.05), and a decrease of approximately the same magnitude in reduced glutathione (P < 0.05) in restrained animals with vehicle exposure. There were no differences observed between control and stress treatment with plant-derived odor exposure in any of the measured parameters. It was concluded that exposure to plant-derived odors reduce corticosterone, glucose, and redox responses elicited by psychological stress.

Effects of exposure to plant-derived odorants on behavior and the concentration of stress-related hormones in steers isolated under a novel environment

This study was conducted to investigate physiological and behavioral effects of the exposure to plant-derived odorants in Holstein steers (8 month of age) under the acute stress of social isolation in a novel environment. Each steer was tethered in a new room alone and exposed to one of three odorants: a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol (green odor, GO; n = 5), essential oil of grapefruits (EOG; n = 5) and solvent (SOL; n = 6). Behaviors were recorded and blood samples were taken at intervals of 10-15 min for 6 h. Compared with SOL, exposure to GO or EOG decreased the frequency of vocalization (P < 0.05), shortened the latency period before the onset of rumination (P < 0.05) and increased the duration of rumination (P < 0.05). Plasma cortisol concentrations in steers exposed to plant-derived odorants (GO and EOG) during 90-130 min from commencement of sampling were significantly lower (P < 0.05) compared with SOL. These results suggest that appeasing effects of plant-derived odorants on behavioral and physiological stress responses previously reported in laboratory rodents could be also be expected in steers.

Occurrence, Sensory Impact, Formation, and Fate of Damascenone in Grapes, Wines, and Other Foods and Beverages

Among plant-derived odorants, damascenone is one of the most ubiquitous, sometimes occurring as an apparent natural product but more commonly occurring in processed foodstuffs and beverages. It has been widely reported as a component of alcoholic beverages, particularly of wines made from the grape Vitis vinifera . Although damascenone has one of the lowest ortho- and retronasal detection thresholds of any odorant, its contribution to the sensory properties of most products remains poorly understood. Damascenone can be formed by acid-catalyzed hydrolyses of plant-derived apocarotenoids, in both aglycon and glycoconjugated forms. These reactions can account for the formation of damascenone in some, but not all, products. In wine, damascenone can also be subject to degradation processes, particularly by reaction with sulfur dioxide.

Hypothalamo-amygdala-prefrontal network in reward seeking

Event Abstract Back to Event Hypothalamo-amygdala-prefrontal network in reward seeking Shuji Aou1*, Kimiya Narikiyo1, Akira Masuda1, Noboru Shiota1 and Takao Inoue1 1 Kyushu Institute of Technology, Department of Brain Science and Engineering, Japan Foods, sexual/social partners, family and friends are essential natural rewards for humans and animals. We are trying to make great efforts to get these rewards, however, the numbers of patients who failed to manipulate these rewards, such as eating disorders, reproductive dysfunctions, emotional disorders, various types of addiction and social dysfunctions including autism and other communication problems are greatly increasing in modern societies under the influences of drastic changes in environments and social systems. It has been studied that the hypothalamo- amygdala-prefrontal network is deeply involved in neural control of reward-seeking behaviors. Hypothalamic neurons show specific responses to different natural rewards. The amygdala plays an important roles in emotional evaluation of rewards and punishments. The orbitofrontal cortex (OFC) has been shown to evaluate reward value based on integration of multimodal sensory inputs and endogenous humoral signals. OFC neurons showed selective responses to each category of rewards. Animal behaviors are highly sensitive to environmental chemicals especially during developing period. Certain artificial chemicals such as environmental endocrine disrupters have aversive effects on normal development of behaviors including reward-seeking behavior through affecting hypothaloamo-amygdala-prefrontal network. In contrast, natural environmental chemicals such as plant-derived odors have beneficial effects on our various behaviors. Dynamic properties of hypothalamo-amygdala-prefrontal network in reward seeking under the influence of chemical environments will be discussed. Conference: IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010. Presentation Type: Oral Presentation Topic: Abstracts Citation: Aou S, Narikiyo K, Masuda A, Shiota N and Inoue T (2010). Hypothalamo-amygdala-prefrontal network in reward seeking. Front. Neurosci. Conference Abstract: IBRO International Workshop 2010. doi: 10.3389/conf.fnins.2010.10.00222 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 May 2010; Published Online: 04 May 2010. * Correspondence: Shuji Aou, Kyushu Institute of Technology, Department of Brain Science and Engineering, Kitakyushu, Japan, aou@brain.kyutech.ac.jp Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Shuji Aou Kimiya Narikiyo Akira Masuda Noboru Shiota Takao Inoue Google Shuji Aou Kimiya Narikiyo Akira Masuda Noboru Shiota Takao Inoue Google Scholar Shuji Aou Kimiya Narikiyo Akira Masuda Noboru Shiota Takao Inoue PubMed Shuji Aou Kimiya Narikiyo Akira Masuda Noboru Shiota Takao Inoue Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effects of Plant-derived Odors on Sleep-Wakefulness and Circadian Rhythmicity in Rats

Plant-derived odorants promote good feeling, refresh spirits and sometimes relieve various stresses in humans. Physiological and psychological effects of plant-derived volatile chemicals have long been acknowledged in folk medicine and aromatherapy. Recent evidence from animal experiments suggests that these plant-derived chemicals affect various animal behaviors via modulating neural or humoral mechanisms (Torii et al., 1988; Sano et al., 1998; Ilmberger et al., 2001; Akutsu et al., 2002; Nakashima et al., 2004). However, the majority of those animal experiments were performed under unusual environmental conditions (various stresses, anesthesia). Therefore, we examined the effects of these odorants on sleep– wakefulness and circadian rhythm in freely moving animals. We used two volatile substances: α-pinene and mixture of green odor (nhexenal and n-hexenol).

The olfactory responses of the antenna and maxillary palp of the fleshfly, Neobellieria bullata (Diptera: Sarcophagidae), and their sensitivity to blockage of nitric oxide synthase

The relative sensitivities of the olfactory receptors in the antenna and maxillary palp of the fleshfly, Neobellieria bullata, were assessed using simultaneous electroantennograms (EAGs) and electropalpograms (EPGs). In general, the antennae and maxillary palps were more sensitive to odors related to animals (blood extract and saturated carboxylic acid) than to odors that were plant-derived (citral, hexenol, hexenal). In addition, the maxillary palps were relatively less sensitive to plant-derived odorants than the antennae, perhaps related to their anatomical position. Scanning electron microscopy was also used to assess the types of sensilla found on the two organs. In addition, NADPH-diaphorase histochemistry was used in an attempt to localize the enzyme nitric oxide synthase (NOS) in the antenna and the maxillary palps. We found evidence of NADPH-diaphorase staining in both organs, with localized staining in the antennal cells and more general staining in the maxillary palps. When NOS was selectively blocked using the antagonist L-NAME, the amplitude of the EAGs and EPGs to odorants fell by 30–50%. In contrast, application of the inactive enantiomer, D-NAME, did not change the amplitude of the EAGs or the EPGs. Our results indicate that NOS is involved in the function of olfactory receptor cells in the fleshfly.

Alleviating effects of plant-derived fragrances on stress-induced hyperthermia in rats

In the present study, the effects of exposure to plant-derived odors on the autonomic and behavioral responses to novel environment were examined in rats. Male rats ( n=42) carrying a telemetry transmitter were individually housed, and on the test day each rat was transferred to a new cage containing bedding that had been sprayed immediately before testing with 200 μl of 0.03% dilution of either lavender essential oil, green leaf odor (a mixture of hexenol and hexenal), alpha-pinene, or solvent (triethyl citrate) as a control. Following the transfer to this novel environment, the body temperature of the rats increased by nearly 1 °C, showing a stress-induced hyperthermia. Stress-induced hyperthermia was attenuated by the green odor and the alpha-pinene, but not by the lavender or solvent. There was no clear effect of fragrances on heart rate or behavioral responses. These results suggest that plant-derived fragrances, such as green odor and alpha-pinene, have calming effects on autonomic stress response to novel environments.