Pheromone Compounds Research Articles

Reproductive Behavior of Copitarsia uncilata (Lepidoptera: Noctuidae).

Copitarsia sp. (Hampson) (Lepidoptera: Noctuidae: Cuculliinae) is a quarantine pest in different countries and affects diverse crops of economic importance in South America. The development of ethological control strategies is an important issue that requires knowing the reproductive behavior of the species involved. Therefore, the aim of this study was to establish the reproductive behavior of Copitarsia uncilata (Burgos & Leiva) and to evaluate the attractiveness of synthetic pheromone compounds under laboratory conditions. Observations of nocturnal reproductive behavior of males and females were performed for 7days in order to register the courtship, mating, and oviposition time. Once the period of the highest reproductive activity was identified, flight behavior and attraction of virgin males were evaluated in a wind tunnel towards synthetic compounds previously reported as commercial pheromones for Copitarsia species, namely (Z)-tetradec-9-enyl acetate (Z9-14Ac), (Z)-tetradec-9-enol (Z9-14OH), and their mixture (Z9-14Ac + Z9-14OH at 4:1 ratio), in comparison with virgin females and clean air flow. We observed that reproductive behavior occurs during the first third of the scotophase and begins on the second day after adult emergence. Highest proportion of courtship and mating occurs on days 2 and 3 after emergence, and oviposition starts the night immediately after the first mating. Wind tunnel assessments showed that males were highly attracted to calling females compared with the blend of synthetic pheromone compounds, with 89% and 12% of males landing at the source, respectively. Moreover, males also showed a low response to the isolated compounds (Z9-14Ac 14% and Z9-14OH 4%).

Olfactory Receptor Neurons for Plant Volatiles and Pheromone Compounds in the Lucerne Weevil, Sitona discoideus

Antennal olfactory receptor neurons (ORNs) for pheromone-related and plant volatile compounds were identified and characterized in the lucerne weevil, Sitona discoideus (Gyllenhal), using the single sensillum recording technique. Our study using five pheromone-related compounds and 42 plant volatile compounds indicates that S. discoideus have highly specialized ORNs for pheromone and plant volatile compounds. Different groups of ORNs present in both males and females of S. discoideus were highly sensitive to 4-methylheptane-3,5-dione (diketone) and four isomers (RR, RS, SR and SS) of 5-hydroxy-4-methylheptan-3-one, respectively. Our results also indicate that male S. discoideus, using the sensory input from antennal ORNs, can distinguish both diketone and the RR-isomer from others, and RS- and SS-isomers from others, although it was unclear if they can distinguish between RS-isomer and SS-isomer, or between diketone and the SR-isomer. It also appeared that female S. discoideus could distinguish between RS-isomer and SS-isomers. The antennae of S. discoideus thus contain sex-specific sets of ORNs for host- and non-host plant volatile compounds. Both sexes of S. discoideus have highly sensitive and selective ORNs for some green-leaf volatiles, such as (Z)-3-hexenol and (E)-2-hexenal. In contrast, male antennae of S. discoideus house three distinct groups of ORNs specialized for myrcene and (E)-β-ocimene, 2-phenylethanol, and phenylacetaldehyde, respectively, whereas female antennae contain three groups of ORNs specialized for (±)-linalool and (±)-α-terpineol, myrcene and (E)-β-ocimene, (±)-1-octen-3-ol, and 3-octanone. Our results suggest that S. discoideus use a multi-component pheromone communication system, and a sex-specific set of ORNs with a narrow range of response spectra for host-plant location.

Sex-specific molecular specialization and activity rhythm-dependent gene expression in honey bee antennae.

We performed an RNA-seq-based comparison of gene expression levels in the antennae of honey bee drones and time-trained foragers (workers) collected at different times of the day and different activity states. Interestingly, olfaction-related genes [i.e. odorant receptor (Or) genes, odorant binding protein (Obp) genes, carboxyl esterase (CEst) genes, etc.] showed stable gene expression differences between drone and worker antennae. Drone antennae showed higher expression of 24 Or genes, of which 21 belong to the clade X which comprises the receptor for the major queen pheromone compound 9-ODA. This high number of drone-biased Or genes suggests that more than previously thought play a role in sex-pheromone communication. In addition, we found higher expression levels for many non-olfaction-related genes including nitric oxide synthase (NOS), and the potassium channel Shaw In contrast, workers showed higher expression of 67 Or genes, which belong to different Or clades that are involved in pheromone communication as well as the perception of cuticular hydrocarbons and floral scents. Further, drone antennae showed higher expression of genes involved in energy metabolism, whereas worker antennae showed higher expression of genes involved in neuronal communication, consistent with earlier reports on peripheral olfactory plasticity. Finally, drones that perform mating flight in the afternoon (innate) and foragers that are trained to forage in the afternoon (adapted) showed similar daily changes in the expression of two major clock genes, period and cryptochrome2 Most of the other genes showing changes with time or onset of daily flight activity were specific to drones and foragers.

Identification of Δ6‐unsaturated, monoenyl type I pheromone compounds from the cashew stem borer Anthistarcha binocularis (Lepidoptera: Gelechiidae)

The cashew stem borer Anthistarcha binocularis (Meyrick) is a major pest in cashew orchards in Brazil. The damage caused by the larvae results in economic losses, and the available chemical control is not suitable because of the endophytic nature of A. binocularis. The identification of the A. binocularis sex pheromone could provide novel applications for the detection and monitoring of this species. Two compounds from female sex gland extracts elicited electrophysiological responses on male antennae. They were identified as dodec-6-en-1-ol and dodec-6-en-1-yl acetate by gas chromatography-mass spectrometry. E/Z stereoisomers of both compounds were synthesized, and the electroantennograms for the synthetic compounds showed the strongest responses for the (E)-stereoisomers of the alcohol and acetate. In a field trial, the E6-12:OH/E6-12:OAc mixture attracted male A. binocularis, whereas the Z6-12:OH/Z6-12:OAc mixture attracted no specimens. The bioactive compounds from the sex pheromone of A. binocularis have been identified as a mixture of two previously unidentified pheromone compounds: E6-12:OH and E6-12:OAc. The mixture of both compounds was attractive to males in preliminary field experiments, and this study is the first report of Δ6-unsaturated monoenyl pheromone compounds in Lepidoptera. © 2019 Society of Chemical Industry.

Functional characterization of odorant receptors from the moth Eriocrania semipurpurella: A comparison of results in the Xenopus oocyte and HEK cell systems

The Xenopus oocyte and the Human Embryonic Kidney (HEK) 293 cell expression systems are frequently used for functional characterization (deorphanization) of insect odorant receptors (ORs). However, the inherent characteristics of these heterologous systems differ in several aspects, which raises the question of whether the two systems provide comparable results, and how well the results correspond to the responses obtained from olfactory sensory neurons in vivo. Five candidate pheromone receptors were previously identified in the primitive moth Eriocrania semipurpurella (Esem) and their responses were characterized in HEK cells. We re-examined the responses of these five EsemORs in Xenopus oocytes. We showed that in both systems, EsemOR1 specifically responded to the plant volatile β-caryophyllene. EsemOR3 responded stronger to the pheromone component (S,Z)-6-nonen-2-ol than to its enantiomer (R,Z)-6-nonen-2-ol, the second pheromone component. However, EsemOR3 also responded secondarily to the plant volatile β-caryophyllene in the oocyte system, but not in the HEK cell system. EsemOR4 was unresponsive in the HEK cells, but responded primarily to (R,Z)-6-nonen-2-ol followed by (S,Z)-6-nonen-2-ol in the oocytes, representing a discovery of a new pheromone receptor in this species. EsemOR5 was broadly tuned in both systems, but the rank order among the most active pheromone compounds and antagonists was different. EsemOR6 showed no response to any compound in either system. We compared the results obtained in the two different heterologous systems with the activity previously recorded in vivo, and performed in situ hybridization to localize the expression of these OR genes in the antennae. In spite of similar results overall, differences in OR responses between heterologous expression systems suggest that conclusions about the function of individual ORs may differ depending on the system used for deorphanization.

Comparison of the Sex Pheromone Composition of Harmonia axyridis Originating from Native and Invaded Areas.

The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), originates from South-East Asia and is now considered as an invasive species at a worldwide scale, with populations encountered in North and South America, Africa, and Europe. Several previous studies suggested that invasive populations display different behavioral and physiological traits, leading to a better fitness than native individuals. H. axyridis sex pheromone was identified recently, but only from individuals established in Europe. In this study, we compare the composition of the female sex pheromone of H. axyridis from two populations: (i) an invasive population in North America, and (ii) a native population in South-East China. We found the females originating from both populations to release in similar proportions the same five pheromonal compounds, namely β-caryophyllene, β-elemene, methyl-eugenol, α-humulene, and α-bulnesene. However, females from the North American strain release all five compounds in larger amount than the Chinese ones. Whether invasive individuals were selected during the process of invasion through their capacity to better call and find sexual partners remains to be confirmed.

EAG Responses of Adult Lobesia botrana Males and Females Collected from Vitis vinifera and Daphne Gnidium to Larval Host-Plant Volatiles and Sex Pheromone.

We analysed electroantennogram (EAG) responses of male and female adults of the European grapevine moth Lobesia botrana (Denis et Schiffermüller) (Lepidoptera: Tortricidae) collected as larvae from grapevine (Vitis vinifera L.) and flax-leaved daphne (Daphne gnidium L.). The host-plant odorants tested were either V. vinifera-specific [1-octen-3-ol, (E)-β-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene], D. gnidium-specific (2-ethyl-hexan-1-ol, benzothiazole, linalool-oxide, ethyl benzanoate), or were shared by both host-plants (linalool, methyl salicylate). Sex pheromone compounds were also tested. The male response to the major pheromone component (E7,Z9-12:Ac) was higher than to any other stimuli, whereas the response to the minor pheromone components (E7,Z9-12:OH and Z9-12:Ac) was not different from the response to the plant odorants. The female response to pheromone was lower or not different from that to plant odorants. Methyl salicylate elicited a higher response in females and (E)-β-farnesene elicited a higher response than several other plant odorants in both sexes. Non-significant interactions between host-plant odorant and sex indicated an absence of sex specialization for host-plant volatile detection. The lack of a significant interaction between plant volatiles and larval host-plants suggested that there was no specialization for plant-volatile detection between V. vinifera and D. gnidium individuals.

Pheromone gland transcriptome of the pink bollworm moth, Pectinophora gossypiella: Comparison between a laboratory and field population.

The pink bollworm, Pectinophora gossypiella, is a world-wide pest of cotton and in some parts of the cotton growing region is controlled by the mating disruption technique using synthetic sex pheromone. The sex pheromone consists of two compounds, (Z,Z)- and (Z,E)-7,11-hexadecadienyl acetates, in about a 50:50 ratio. However, recently, a population with sex pheromone compound ratios of about 62:38 were found in cotton fields that use mating disruption in Israel. To investigate how the change developed, we compared the pheromone gland transcriptomes between a reference laboratory population and a population obtained from an Israeli cotton field utilizing mating disruption. We analyzed four biological replicates from each population and found transcripts encoding 17 desaturases, 8 reductases, and 17 candidate acetyltransferases in both populations, which could be involved in sex pheromone biosynthesis. The expression abundance of some genes between the two populations was different. Some desaturases and candidate acetyltransferases were found to have mutated in one of the populations. The differentially expressed genes play potential roles in sex pheromone biosynthesis and could be involved in causing altered female sex pheromone ratios in the field population.

Using synthetic semiochemicals to train canines to detect bark beetle\u2013infested trees

Key messageThe dog detection allows timely removal by sanitation logging of first beetle-attacked trees before offspring emergence, preventing local beetle increases. Detection dogs rapidly learned responding to synthetic bark beetle pheromone components, with known chemical titres, allowing search training during winter in laboratory and field. Dogs trained on synthetics detected naturally attacked trees in summer at a distance of > 100 m.ContextAn early detection of first beetle-attacked trees would allow timely sanitation felling before offspring emergence, curbing local beetle increase.AimsWe tested if detection dogs, trained off-season on synthetic pheromone components from Ips typographus, could locate naturally bark beetle–infested spruce trees.MethodsIndoor training allowed dogs to discriminate between the infestation odours (target) and natural odours (non-target) from the forest. Odour stimuli were shown by chemical analysis to be bioactive at extremely low-levels released (< 10−4 ng/15 min) in the laboratory.ResultsDetection dogs, trained to recognise four different synthetic pheromone compounds in the wintertime, were able to detect naturally infested spruce trees unknown to humans the following summer. The dog-handler pairs were able to detect an infested spruce tree from the first hours of beetle attack until several weeks after first attack, long before discolouration of the crown. Trained sniffer dogs detected infested spruce trees out to ≥ 100 m, as measured by GPS-collar tracks.ConclusionDog-handler pairs appear to be more efficient than humans alone in timely detecting bark beetle infestations due to the canine’s ability to cover a greater area and detect by olfaction infestations from a far longer distance than can humans.

Linoleic acid and stearic acid are biosynthetic precursors of (7Z,10Z)-7,10-hexadecadienal, the major component of the sex pheromone of Chilecomadia valdiviana (Lepidoptera: Cossidae).

The main pheromone compound of Chilecomadia valdiviana (Lepidoptera: Cossidae) has been recently identified as (7Z,10Z)-7,10-hexadecadienal. The biosynthesis of this pheromone compound showing attributes of both Type I and Type II lepidopteran pheromones was studied by the topical application of isotope-labeled fatty acids to the pheromone gland and subsequent analysis of the gland contents (pheromone compounds and fatty acyl compounds) by gas chromatography-mass spectrometry. The deuterium label of D11-linoleic acid was incorporated into the pheromone compound and its putative acyl precursor (7Z,10Z)-7,10-hexadecadienoate, demonstrating that the pheromone compound is biosynthesized from linoleic acid by chain-shortening and further functional group transformation. Furthermore, the deuterium label of D3-stearic acid was also incorporated into the pheromone compound, which indicates that the pheromone can be synthesized de novo by C. valdiviana, as is the case for Type I lepidopteran pheromone compounds.

The Combined Use of an Attractive and a Repellent Sex Pheromonal Component by a Gregarious Parasitoid.

Gregarious parasitoids usually clump their cocoons together and the adults emerge in a synchronized fashion. This makes it easy for them to find mating partners and most copulations indeed take place at the natal patch. Yet, males should leave such sites when females are no longer receptive. As yet, this decision-making process and the possible involvement of pheromones were poorly understood. Here we report on a remarkable use of attractive and repellent pheromones of the well-studied gregarious parasitoid species Cotesia glomerata (L.) (Hymenoptera: Braconidae). Virgin C. glomerata females were found to release an attractive as well as a repellent compound, which in combination arrest males on the natal patch, but after mating the females stop the production of the attractant and the males are repelled. The repellent compound was identified as heptanal, which was also released by males, probably reducing male-male competition on the natal patch. We also confirmed that the sex ratio of the emerging wasps can vary considerably among patches, depending on the relative quality of hosts and the number of females that parasitize a host. The newly revealed use of attractive and repellent pheromone compounds by C. glomerata possibly helps maximize mating success under these variable conditions.

Initial Location Preference Together with Aggregation Pheromones Regulate the Attack Pattern of Tomicus brevipilosus (Coleoptera: Curculionidae) on Pinus kesiya

Research Highlights: We found that the initial attack location together with the aggregation pheromones played an important role in mediating the aggressive behavior of T. brevipilosus on P. kesiya. Background and Objectives: T. brevipilosus was identified as an aggressive species, which possesses the ability to kill live, healthy P. kesiya. In this scenario, we study the top-down attack pattern of T. brevipilosus on P. kesiya during the entirety of the reproductive period. Materials and Methods: We investigated the phenology of trunk attack on P. kesiya over a period of three years in Pu’er City, China. The hindguts extracts of the females and males T. brevipilosus were analyzed by coupled gas chromatography-mass spectrometry (GC-MS). The candidate aggregation pheromone compounds of T. brevipilosus were determined through electrophysiology experiments (electroantennographic detection, EAD and electroantennography, EAG), laboratory olfactometer bioassays, and field trapping. Results: we found that the pioneer beetles preferentially infested the crown of P. kesiya at the early stage of attack following spring flight with the later arriving beetles selectively attacking the lower area of the trunk to avoid intraspecific competition and better utilize limited resources, which exhibits a top-down attack pattern. During gallery initiation, the beetles release aggregation pheromones to attract conspecifics to conduct a mass attack. The chemical analyses indicated that the hindgut extracts of gallery-initiating beetles contained a larger amount of myrtenol, cis-verbenol, trans-verbenol, and verbenone. Myrtenol and trans-verbenol were identified as candidate aggregation pheromone compounds. In addition, a blend of these two components with S-(−)-α-pinene and S-(−)-β-pinene attracted more T. brevipilosus individuals in a field bioassay. Conclusions: We concluded that the preference for the initial attack location together with the aggregation pheromones played an important role in mediating the top-down attack pattern of T. brevipilosus on P. kesiya.

Multisensory Logic of Infant-Directed Aggression by Males

Newborn mice emit signals that promote parenting from mothers and fathers but trigger aggressive responses from virgin males. Although pup-directed attacks by males require vomeronasal function, the specific infant cues that elicit this behavior are unknown. We developed a behavioral paradigm based on reconstituted pup cues and showed that discrete infant morphological features combined with salivary chemosignals elicit robust male aggression. Seven vomeronasal receptors were identified based on infant-mediated activity, and the involvement of two receptors, Vmn2r65 and Vmn2r88, in infant-directed aggression was demonstrated by genetic deletion. Using the activation of these receptors as readouts for biochemical fractionation, we isolated two pheromonal compounds, the submandibular gland protein C and hemoglobins. Unexpectedly, none of the identified vomeronasal receptors and associated cues were specific to pups. Thus, infant-mediated aggression by virgin males relies on the recognition of pup's physical traits in addition to parental and infant chemical cues.

The sex pheromone of Legume Pod Borer, Maruca vitrata (Lepidoptera: Crambidae) Revisited

ABSTRACT Female produced sex pheromone of Maruca vitrata containing three components had been reported from countries in tropical Asia and sub-Saharan Africa. (E,E)-10,12-hexadecadienal as a major component, (E,E)-10,12-hexadecadienol and E-10-hexadecenal as minor components blended in the ratio of 100:5:5 was found to attract M. vitrata male moths in few countries in West Africa. However, this blend was found to have less or no effectiveness in trapping M. vitrata population in Asia, which triggered the need to refine the M. vitrata pheromone formulation. The isomers of major and minor pheromone compounds of M. vitrata were evaluated in this study. When subjected to Electroantennogram (EAG) analysis against male antennae, the isomer (Z,E)-10,12-hexadecadienal as a major component blended with the minor components (E,E)-10,12-hexadecadienol and (E)-10-hexadecenol in 100:10:5 was found to elicit better antennal response than the standard three component blend. GC-EAD profiles of the individual synthetic isomer components supported the EAG results. Additional experiments also confirmed the attraction of M. vitrata pheromone compounds and their isomers along with host plant volatiles in EAG and wind-tunnel experiments. Field experiments in India and Cambodia confirmed the effectiveness of improved M. vitrata pheromone lures in attracting the adult male moths in legume fields.

Behavioral and physiological response of male Callisphyris apicicornis (Coleoptera: Cerambycidae) to virgin con-specific females&amp;#8217; extracts

Callisphyris apicicornis (Fairmaire & Germain) (Coleoptera: Cerambycidae: Necydalinae) is a native, xylophagous, and polyphagous longhorned beetle, currently having the status of an increasing pest in some fruit orchards in Chile which needs a control strategy. However, no efficient methods have been developed against C. apicicornis. Since pheromone- based strategies are promissory against these types of pests, it is necessary to understand the chemical communication within this species in order to collect and identify the pheromonal compounds as the first step to develop pheromone- based control tactics. The objectives of this work were to study behavioral and electrophysiological responses of males to con-specific females and its extracts, to seek out evidence of chemical communication in the intraspecific relationship of C. apicicornis. In field, we collected 112 males using 8 baited traps with alive females in two separate experiments. However, neither males nor headspace (HS) extracts were attractive for either sex in field, no males were captured in those treatments (16 traps). On the other hand, in laboratory bioassays males showed significant electroantennographic responses to females’ volatiles extracts (1.46 mV) and gland extracts (1.15 mV). Likewise, behavioral bioassay showed significant olfactometric preference for females’ volatiles and gland extracts. Our results strongly suggest a female- produced sex attractant occurs within this species, so further studies should attempt to identify and quantify the chemicals compounds with this role

Insect Pheromone Receptors - Key Elements in Sensing Intraspecific Chemical Signals.

Pheromones are chemicals that serve intraspecific communication. In animals, the ability to detect and discriminate pheromones in a complex chemical environment substantially contributes to the survival of the species. Insects widely use pheromones to attract mating partners, to alarm conspecifics or to mark paths to rich food sources. The various functional roles of pheromones for insects are reflected by the chemical diversity of pheromonal compounds. The precise detection of the relevant intraspecific signals is accomplished by specialized chemosensory neurons housed in hair-like sensilla located on the surface of body appendages. Current data indicate that the extraordinary sensitivity and selectivity of the pheromone-responsive neurons (PRNs) is largely based on specific pheromone receptors (PRs) residing in their ciliary membrane. Besides these key elements, proper ligand-induced responses of PR-expressing neurons appear to generally require a putative co-receptor, the so-called “sensory neuron membrane protein 1” (SNMP1). Regarding the PR-mediated chemo-electrical signal transduction processes in insect PRNs, ionotropic as well as metabotropic mechanisms may be involved. In this review, we summarize and discuss current knowledge on the peripheral detection of pheromones in the olfactory system of insects with a focus on PRs and their specific role in the recognition and transduction of volatile intraspecific chemical signals.

Identification of Cuticular Pheromonal Compounds from Leaf Beetle, Alticini sp.

Identification of Cuticular Pheromonal Compounds from Leaf Beetle, Alticini sp.

Identification and field evaluation of female sex pheromone of leaf-eating caterpillar, Opisina arenosella (Lepidoptera: Oecophoridae)

AbstractThe leaf-eating caterpillar,Opisina arenosellaWalker, is the most destructive pest of coconut palm in India and Southeast Asia. The management practices employed againstO. arenosellaso far have been unsuccessful in many instances in India, due to the pest behaviour and coconut palm phenology. The life cycle, incidence and behaviour ofO. arenosellaare rather interesting and useful for the intervention of pheromone trapping technique for its management. We conducted the present study with the intention of identifying the female sex pheromone ofO. arenosellaand testing its efficacy under field conditions. Gas chromatography coupled electroantennographic detection (GC–EAD) and gas chromatography–mass spectrometry (GC–MS) analysis of female pheromone glands extract of one-day-oldO. arenosellafemales confirmed the presence of (Z,Z,Z)-3,6,9-tricosatriene (Z3Z6Z9-23Hy) as the dominant sex pheromone component. The male antennal response to female pheromone gland extract and syntheticZ3Z6Z9-23Hy was recorded using GC–EAD, and the results revealed that antennal response was positive to both the treatments at 0.13 mV and 0.14 mV respectively, compared to control (air), which was 0.016 mV. It was also evident from wind-tunnel experiments that the male moth response was high (80%) with the female gland extract, compared to 60% with synthetic pheromone and 0% for control (air). Male moths caught in the traps with and without lure were assessed in two field sites and recorded 69.26% and 54.25% more moth catches in the traps with the lure. We also observed a similar result in the cage experiment in which male moths caught in the traps with and without lure were 64.50% and 12.40%, respectively. The study also confirmed that 93.20% moths caught in the pheromone-baited traps were male. From the study, it is evident that the presence of (Z,Z,Z)-3,6,9-tricosatriene, which is the sex pheromone compound from the female gland extract ofO. arenosella, is an effective attractant in pheromone traps for the male moth under field conditions.

Evidence of Male Pheromone in Conogethes punctiferalis (Lepidoptera: Pyralidae)

Conogethes punctiferalis Guenee is a polyphagous insect pest that is difficult to manage because it feeds within plant tissue. Management by mass trapping using semiochemicals, especially pheromones, represents a viable option to control such borers. Herein, pheromonal compounds were extracted from male and female moths and assessed using headspace sampling and electroantennogram response. One-d-old C. punctiferalis showed a higher response to volatile solvents than 4-d-old ones, irrespective of sex. The male antenna was found more sensitive than the female for volatile compounds. However, the female response to male headspace extract and abdominal tip extract was very high (i.e., 4.006 mV and 2.217 mV, respectively), which revealed the presence of males producing a female-attracting olfactory cue in C. punctiferalis. This was also confirmed by males calling the female before mating by extruding the hair pencils in their abdominal tip. The male pheromone extract when analyzed in gas chromatography–mass spectrometry indicated the presence of methyl acetophenone or 3-ethyl acetophenone.

Three chemosensory proteins from the rice leaf folder Cnaphalocrocis medinalis involved in host volatile and sex pheromone reception.

Chemosensory proteins (CSPs) have been considered to play a key role in chemoreception in insects. As stated in our earlier study, three CSP genes from rice leaf folder Cnaphalocrocis medinalis have been identified and showed potential physiological functions in olfaction. Here, we conducted western blot, immunolocalization, competitive binding assay and knockdown assay by RNA interference both in vitro and in vivo to reveal the functions of these three CSPs in C.medinalis. Results showed that both CmedCSP1 and CmedCSP2 are housed in sensilla basiconica and showed high binding affinities to a wide range of host-related semiochemicals. On the other hand, CmedCSP3 is highly expressed in sensilla trichodea of males and sensilla basiconica of females. It showed binding affinities to plant volatiles, especially terpenoids, as well as two of the C.medinalis sex pheromone components, Z11-16:Ac and Z11-16:Al. The transcript expression level of the three CSP genes significantly decreased after injecting target double-stranded RNAs and resulted in remarkably down-regulation on electroantennogram responses evoked by host-related semiochemicals and one sex pheromone compound, which have high binding affinities with CmedCSPs. In conclusion, the three CmedCSPs tested are involved in C.medinalis reception of semiochemicals, including host attractants and sex pheromones.