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The zoophytophagous mirid predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is used in the augmentative biological control of Thrips palmi Karny (Thysanoptera: Thripidae), a fruit and vegetable pest in protected culture in Japan. N. tenuis can be maintained on certain plants without arthropod prey. Although such plant species may be useful as banker plants, their attractiveness to N. tenuis is underresearched. We investigated the behavioral responses of N. tenuis to (1) uninfested and conspecific-infested banker plants, Verbena × hybrida (verbena), Scaevola aemula (scaevola), Cleome hassleriana (cleome), and Lobularia maritima (sweet alyssum) and (2) conspecific-infested banker plants and T. palmi-infested eggplants, using a Y-tube olfactometer. Female N. tenuis preferred the volatiles emitted by (1) uninfested verbena over clean air but showed no preference for those emitted by the other uninfested banker plants, and (2) conspecific-infested verbena over clean air but showed no preference for those emitted by conspecific-infested scaevola over clean air. The attractiveness of the volatiles of T. palmi-infested eggplants for N. tenuis was not significantly different from those of N. tenuis-infested verbena and scaevola. As both uninfested and conspecific-infested verbena attracted female N. tenuis, this species is a promising banker plant. Chemical analyses and principal coordinate analyses of the volatiles from the headspaces of uninfested and N. tenuis-infested verbena and scaevola showed that 1-octen-3-ol, (E)-β-caryophyllene, and (E)-4,8-dimethyl-1,3,7-nonatriene distinguished these plant species and are candidate volatile N. tenuis attractants. [ABSTRACT FROM AUTHOR]

BACKGROUND: General odor‐binding proteins (GOBPs) play critical roles in insect olfactory recognition of sex pheromones and plant volatiles. Therefore, the identification of GOBPs in Hyphantria cunea (Drury) based on their characterization to pheromone components and plant volatiles is remain unknown. RESULTS: In this study, two H. cunea (HcunGOBPs) genes were cloned, and their expression profiles and odorant binding characteristics were systematically analyzed. Firstly, the tissue expression study showed that both HcunGOBP1 and HcunGOBP2 were highly expressed in the antennae of both sexes, indicating their potential involvement in the perception of sex pheromones. Secondly, these two HcunGOBPs genes were expressed in Escherichia coli and ligand binding assays were used to assess the binding affinities to its sex pheromone components including two aldehydes and two epoxides, and some plant volatiles. HcunGOBP2 showed high binding affinities to two aldehyde components (Z9, Z12, Z15‐18Ald and Z9, Z12‐18Ald), and showed low binding affinities to two epoxide components (1, Z3, Z6‐9S, 10R‐epoxy‐21Hy and Z3, Z6‐9S, 10R‐epoxy‐21Hy), whereas HcunGOBP1 showed weak but significant binding to all four sex pheromone components. Furthermore, both HcunGOBPs demonstrated variable binding affinities to the plant volatiles tested. Thirdly, in silico studies of HcunGOBPs utilized homology, structure modeling, and molecular docking revealed critical hydrophobic residues might be involved in the binding of HcunGOBPs to their sex pheromone components and plant volatiles. CONCLUSION: Our study suggests that these two HcunGOBPs may serve as potential targets for future studies of HcunGOBPs ligand binding, providing insight in the mechanism of olfaction in H. cunea. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

An electroantennogram (EAG) technique compared the antennal olfactory responses by both sexes of eight Japanese Papilio species with known host plants in laboratory experiments. Papilio species were collected from Honshû and Kyûshû (Japanese islands). The behavioral responses to volatile leaf substances from Citrus deliciosa, Zanthoxylum ailanthoides, Phellodendron amurense, Orixa japonica, and Foeniculum vulgare were examined in laboratory experiments. Individual EAG reactions were recorded. The results were very similar to the empirical field observations. The electrophysiological results of both sexes showed that the volatile substances released from non-preferred plants mainly elicited more significant EAG responses than the volatile substances from preferred host plants. Moreover, we performed behavioral experiments using eight female butterflies and their responses to five host plant species. An association between host plant selection behavior and taxonomical classification exists within the Papilio genus. The EAG responses were small when exposed to the plants with high scores in the behavioral experiments. Host plant preference patterns seem to be related to the volatile substances within the host plants. The butterflies responded to Linalool in both the behavioral and electrophysiological experiments. [ABSTRACT FROM AUTHOR]

Water is essential to plant growth and drives plant evolution and interactions with other organisms such as herbivores. However, water availability fluctuates, and these fluctuations are intensified by climate change. How plant water availability influences plant–herbivore interactions in the future is an important question in basic and applied ecology. Here we summarize and synthesize the recent discoveries on the impact of water availability on plant antiherbivore defense ecology and the underlying physiological processes. Water deficit tends to enhance plant resistance and escape traits (i.e. early phenology) against herbivory but negatively affects other defense strategies, including indirect defense and tolerance. However, exceptions are sometimes observed in specific plant–herbivore species pairs. We discuss the effect of water availability on species interactions associated with plants and herbivores from individual to community levels and how these interactions drive plant evolution. Although water stress and many other abiotic stresses are predicted to increase in intensity and frequency due to climate change, we identify a significant lack of study on the interactive impact of additional abiotic stressors on water–plant–herbivore interactions. This review summarizes critical knowledge gaps and informs possible future research directions in water–plant–herbivore interactions. [ABSTRACT FROM AUTHOR]

Abstract Background Endoclita signifer causes severe damage to eucalyptus plantations, and the larvae transfer to and damage eucalyptus accurately in mixed forests, suggesting that the larval olfactory system contributes to host selection. The olfactory proteins in the head and tegument of E. signifer larvae were previously identified. To identify the relationship between olfactory protein expression in the larval head the larvae head and the developmental expression dynamics, and its functions in further recognition of plant volatiles, the head transcriptomes of two instar larvae and the expression profiles of olfactory proteins in the instars after exposure to volatiles were studied. Results Eight odorant-binding proteins, six chemosensory proteins, three odorant receptors, three gustatory receptors, and 18 ionotropic receptors were identified. Half of the olfactory proteins were the most highly expressed in the young (5th) larval head, and EsigGOBP2, EsigGOBP4, EsigGOBP5, EsigCSP1, EsigCSP3, EsigGR1 and EsigGR3 were highly expressed and showed a specific expression pattern. In addition, after exposure to o-cymene, α-phellandrene, n-butyl ether, and 4-ethylacetophenone, EsigGR3 was downregulated significantly, and exposure to n-butyl ether caused EsigGR1 to be downregulated significantly. Conclusions Seven specific olfactory proteins may be important genes in larval olfactory recognition. Furthermore, based on the receptors that were downregulated after exposure to volatiles and the previous electrophysiological activity in the third larvae, we speculated that the ligand of EsigGR1 was n-butyl ether, and the ligands of the newly identified EsigGR3 are all electrophysiologically active compounds, which demonstrated host recognition in the third larvae of E. signifer. These results provide a way to find key plant volatiles recognized by the key olfactory proteins as new targets for pest control. Graphical Abstract

Aroma (volatile) compounds play important ecological functions in plants, and also contribute to the quality of plant-derived foods. Moreover, chiral aroma compounds affect their functions in plants and lead to different flavor quality properties. Formations of chiral aroma compounds are due to the presence of enzymes producing these compounds in plants, which are generally involved in the final biosynthetic step of the aroma compounds. Here, we review recent progress in research on the plant-derived enzymes producing chiral aroma compounds, and their changes in response to environmental factors. The chiral aroma enzymes that have been reported produce (R)-linalool, (S)-linalool, (R)-limonene, and (S)-limonene, etc., and these enzymes are found in various plant species. We also discuss the origins of enantioselectivity in the plant-derived enzymes producing chiral aroma compounds and summarize the potential use of plants containing enzymes producing chiral aroma compounds for producing chiral flavors/fragrances. [ABSTRACT FROM AUTHOR]

Jasmonic acid (JA) regulates the production of several plant volatiles that are involved in plant defense mechanisms. In this study, we report that the JA-responsive volatile apocarotenoid, β-cyclocitral (β-cyc), negatively affects abscisic acid (ABA) biosynthesis and induces a defense response against Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight in rice (Oryza sativa L.). JA-induced accumulation of β-cyc was regulated by OsJAZ8, a repressor of JA signaling in rice. Treatment with β-cyc induced resistance against Xoo and upregulated the expression of defense-related genes in rice. Conversely, the expression of ABA-responsive genes, including ABA-biosynthesis genes, was downregulated by JA and β-cyc treatment, resulting in a decrease in ABA levels in rice. β-cyc did not inhibit the ABA-dependent interactions between OsPYL/RCAR5 and OsPP2C49 in yeast cells. Furthermore, we revealed that JA-responsive rice carotenoid cleavage dioxygenase 4b (OsCCD4b) was localized in the chloroplast and produced β-cyc both in vitro and in planta. These results suggest that β-cyc plays an important role in the JA-mediated resistance against Xoo in rice. [ABSTRACT FROM AUTHOR]

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We investigated the biogenic volatile organic compound (BVOC) emission rates and composition of Cupressaceae species and how the emissions change in response to moderate warming and more severe heat stress. A total of 8 species from 7 distinct Cupressaceae genera were targeted in this study and exposed to laboratory-simulated heatwaves. Each plant was enclosed in a temperature-controlled glass chamber and allowed to equilibrate at 30 °C for 24 h. The temperature was then increased stepwise from 33 °C to 43 °C in 2 °C increments, with each step lasting 2 h, and was finally kept at 45 °C for 12 h. The BVOC emissions were measured periodically using an automated air sampler coupled to a gas chromatograph. Most of the sampled Cupressaceae species (6 out of 8) were low BVOC emitters (<0.3 μgC g -1  h -1 ) at 30 °C. However, the BVOC emissions of all 8 species increased strongly with temperature, and in most species (5 out of 8), the emissions continued to increase with longer exposure times to heat stress. The largest increase was observed in Thuja occidentalis and Chamaecyparis thyoides, which reached maximum emissions of 350 and 190 μgC g -1  h -1 , respectively. Of the different BVOCs, monoterpenes responded most strongly to heat stress, with Q 10 temperature coefficients typically ranging between 7.6 and 22, which were significantly greater than the model-predicted value of 2.7. Other BVOCs including sesquiterpenes, C 9 aromatics (only detected in Calocedrus decurrens), methylbutenols, and other C 5 oxygenates were also induced by heat stress, but generally at a lower magnitude than monoterpenes. Our results indicate that Cupressaceae are a large but typically dormant source of reactive volatile hydrocarbons (mostly monoterpenes) whose emissions can be activated by heat stress. This phenomenon could have important implications for ozone and aerosol formation, air quality, and human health, particularly in urban areas that are prone to heatwaves., (Copyright © 2024. Published by Elsevier B.V.)

Fruit volatiles play a crucial role in the host localization by the oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae). This study focused on identifying the fruit volatiles from Sanyue plum and Sanhua plum (Prunus salicina Lindl.), which are 2 varieties of the same species, and examined their impact on the behavior of B. dorsalis by using a Y-olfactometer. A total of 35 and 54 volatiles from Sanyue plum and Sanhua plum were identified, respectively. Among these, 23 volatiles elicited electroantennographic (EAG) responses by B. dorsalis adults, showing concentration-dependent effects in males and females. Ethyl butyrate, butyl acetate, butyl hexanoate, ethyl caproate, ethyl hexanoate, and hexyl acetate significantly attracted B. dorsalis compared to liquid paraffin, while nonaldehyde was avoided. There was no significant difference in the behavioral responses of both sexes to sorbitol esters, hexyl isobutyrate, and 1-tetradecene compared with the control liquid paraffin group. Interestingly, (3Z)-C-3-hexenyl acetate significantly attracted females, but not males. The above findings suggest that plum fruit volatiles are likely to facilitate the localization of host fruit by B. dorsalis adults and may even aid in mate-finding. This study opens up new avenues for exploring novel plant-based attractants that might be of value for the integrated management of B. dorsalis., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: Endoclita signifer causes severe damage to eucalyptus plantations, and the larvae transfer to and damage eucalyptus accurately in mixed forests, suggesting that the larval olfactory system contributes to host selection. The olfactory proteins in the head and tegument of E. signifer larvae were previously identified. To identify the relationship between olfactory protein expression in the larval head the larvae head and the developmental expression dynamics, and its functions in further recognition of plant volatiles, the head transcriptomes of two instar larvae and the expression profiles of olfactory proteins in the instars after exposure to volatiles were studied. Results: Eight odorant-binding proteins, six chemosensory proteins, three odorant receptors, three gustatory receptors, and 18 ionotropic receptors were identified. Half of the olfactory proteins were the most highly expressed in the young (5th) larval head, and EsigGOBP2, EsigGOBP4, EsigGOBP5, EsigCSP1, EsigCSP3, EsigGR1 and EsigGR3 were highly expressed and showed a specific expression pattern. In addition, after exposure to o-cymene, α-phellandrene, n-butyl ether, and 4-ethylacetophenone, EsigGR3 was downregulated significantly, and exposure to n-butyl ether caused EsigGR1 to be downregulated significantly. Conclusions: Seven specific olfactory proteins may be important genes in larval olfactory recognition. Furthermore, based on the receptors that were downregulated after exposure to volatiles and the previous electrophysiological activity in the third larvae, we speculated that the ligand of EsigGR1 was n-butyl ether, and the ligands of the newly identified EsigGR3 are all electrophysiologically active compounds, which demonstrated host recognition in the third larvae of E. signifer. These results provide a way to find key plant volatiles recognized by the key olfactory proteins as new targets for pest control. [ABSTRACT FROM AUTHOR]

BACKGROUND: Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an important natural enemy of aphids. Plant species and plant health conditions can affect the behavior of H. axyridis. To determine plant effects on this lady beetle, we examined beetle responses to four cover crops: coriander (Coriadrum sativum L., Apiales: Apiaceae), marigold (Tagetes erecta L., Asterales: Asteraceae), sweet alyssum (Lobularia maritima L., Brassicales: Brassicaceae), and alfalfa (Medicago sativa L., Fabales: Fabaceae). Our goal was to better understand this predator's ovipositional behavior in response to different plants and its olfactory response to the aphid‐induced volatiles from these plants. RESULTS: We found that this lady beetle did not have any significant oviposition preference among the four plant species, but H. axyridis preferred to lay eggs on the lower surface of leaves, regardless of the plant species. H. axyridis females had a significant preference for aphid‐infested marigolds, but were not attracted by any of the other three cover plants or marigolds without aphid damage. Compared to the uninfested marigold plants, the emission of 12 compounds significantly increased on the aphid‐infested marigolds, and two of them were attractive to H. axyridis under suitable concentrations. CONCLUSION: H. axyridis did not show any significant oviposition preference among the four cover crops. Aphid‐infested marigolds can attract H. axyridis. Indole and terpinen‐4‐ol mediated lady beetle attraction. These synomones have potential for manipulating populations of H. axyridis as a component of conservation biological control. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Parasitoid foraging behavior is affected by habitat and host plant differences. Egg parasitoids also use a combination of oviposition-induced and host-derived cues to find host eggs. This study compared parasitism by Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae) on two squash bug species, Anasa tristis (DeGeer) and Anasa armigera Say (Hemiptera: Coreidae), by placing sentinel squash and cucumber plants with egg masses of either of the two squash bug species in squash and cucumber fields in a 3-way factorial design. Host density of wild A. tristis egg masses in squash fields may have influenced parasitoid foraging behavior on sentinel plants. In the 3-way factorial design, parasitism was higher on sentinel squash plants and in squash fields overall. However, parasitism on A. armigera egg masses was highest on sentinel cucumber plants in squash fields and parasitism on A. tristis egg masses was higher on sentinel squash plants in either squash or cucumber fields and lowest on sentinel cucumber plants in cucumber fields. Results suggest that parasitoids were able to specifically orient to the combination of host plant and host cues associated with A. tristis egg masses on sentinel squash plants, but that they were more responsive to plant-induced cues associated with cucumber when searching for A. armigera egg masses. Parasitoids appear to utilize different combinations of host plant and host cues when searching for eggs of the two squash bug species. [ABSTRACT FROM AUTHOR]

Stomata play a central role in plant responses to abiotic and biotic stresses. Existing knowledge regarding the roles of stomata in plant stress is centered on abiotic stresses and plant–pathogen interactions, but how stomata influence plant–herbivore interactions remains largely unclear. Here, we summarize the functions of stomata in plant–insect interactions and highlight recent discoveries of how herbivores manipulate plant stomata. Because stomata are linked to interrelated physiological processes in plants, herbivory-induced changes in stomatal dynamics might have cellular, organismic, and/or even community-level impacts. We summarize our current understanding of how stomata mediate plant responses to herbivory and environmental stimuli, propose how herbivores may influence these responses, and identify key knowledge gaps in plant–herbivore interactions. Plant stomata are emerging as important mediators of interactions between plants and herbivores. Several components in the oral secretions of herbivores, such as enzymes and phytohormones, that can trigger herbivory-induced stomatal closure have been identified. Recent evidence suggests that herbivory-induced stomatal changes play important roles in mediating interactions among plants, herbivores, pathogens, and the environment. [ABSTRACT FROM AUTHOR]

Abstract Background Most plant viruses rely on vectors for their transmission and spread. One of the outstanding biological questions concerning the vector-pathogen-symbiont multi-trophic interactions is the potential involvement of vector symbionts in the virus transmission process. Here, we used a multi-factorial system containing a non-persistent plant virus, cucumber mosaic virus (CMV), its primary vector, green peach aphid, Myzus persicae, and the obligate endosymbiont, Buchnera aphidicola to explore this uncharted territory. Results Based on our preliminary research, we hypothesized that aphid endosymbiont B. aphidicola can facilitate CMV transmission by modulating plant volatile profiles. Gene expression analyses demonstrated that CMV infection reduced B. aphidicola abundance in M. persicae, in which lower abundance of B. aphidicola was associated with a preference shift in aphids from infected to healthy plants. Volatile profile analyses confirmed that feeding by aphids with lower B. aphidicola titers reduced the production of attractants, while increased the emission of deterrents. As a result, M. persicae changed their feeding preference from infected to healthy plants. Conclusions We conclude that CMV infection reduces the B. aphidicola abundance in M. persicae. When viruliferous aphids feed on host plants, dynamic changes in obligate symbionts lead to a shift in plant volatiles from attraction to avoidance, thereby switching insect vector’s feeding preference from infected to healthy plants.

Insects produce pheromones to serve a range of ecological functions throughout their lifetime. The chemical composition, production pattern, and interspecies specificity provide information for carrying out their function and biological significance. Several species of Drosophila produce a class of volatile esters considered as "fruity smells"; however, the production pattern and ecological functions of these "fruity smell" volatiles in genus Drosophila are poorly understood. Here, using the headspace solid‐phase microextraction (SPME) method, we tested the production pattern of volatile pheromones in Drosophila immigrans and factors that possibly affected pheromone production, including mating, feeding conditions, age of adult flies, and geographical distribution. We also explored the evolution and production pattern of volatile pheromones in 14 species of genus Drosophila. Our result showed that male D. immigrans adult flies produce three male‐specific volatile ester pheromones, which are also considered as "fruity smell" chemicals, in a relatively stable pattern. In addition, a series of "fruity smell" ester pheromones with similar structure and chemical properties were found to appear in the species of D. virilis and D. immigrans species group, but not in the species of D. melanogaster species group. The ester volatile pheromone production of male flies has a correspondence with the female's demand for host plants. Integrating the production and evolution pattern of these volatile chemicals, we inferred the interaction between insects and host plants reflected in the Drosophila "fruity smell" pheromones. [ABSTRACT FROM AUTHOR]

Jasmonic acid (JA) regulates the production of several plant volatiles that are involved in plant defense mechanisms. In this study, we report that the JA-responsive volatile apocarotenoid, β-cyclocitral (β-cyc), negatively affects abscisic acid (ABA) biosynthesis and induces a defense response against Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight in rice (Oryza sativa L.). JA-induced accumulation of β-cyc was regulated by OsJAZ8, a repressor of JA signaling in rice. Treatment with β-cyc induced resistance against Xoo and upregulated the expression of defense-related genes in rice. Conversely, the expression of ABA-responsive genes, including ABA-biosynthesis genes, was downregulated by JA and β-cyc treatment, resulting in a decrease in ABA levels in rice. β-cyc did not inhibit the ABA-dependent interactions between OsPYL/RCAR5 and OsPP2C49 in yeast cells. Furthermore, we revealed that JA-responsive rice carotenoid cleavage dioxygenase 4b (OsCCD4b) was localized in the chloroplast and produced β-cyc both in vitro and in planta. These results suggest that β-cyc plays an important role in the JA-mediated resistance against Xoo in rice.

Abstract Background While virus-vector-host interactions have been a major focus of both basic and applied ecological research, little is known about how different levels of plant defense interact with prior herbivory to affect these relationships. We used genetically-modified strains of tomato (Solanum lycopersicum) varying in the jasmonic acid (JA) plant defense pathways to explore how plant defense and prior herbivory affects a plant virus (tomato yellow leaf curl virus, ‘TYLCV’), its vector (the whitefly Bemisia tabaci MED), and the host. Results Virus-free MED preferred low-JA over high-JA plants and had lower fitness on high-JA plants. Viruliferous MED preferred low-JA plants but their survival was unaffected by JA levels. While virus-free MED did not lower plant JA levels, viruliferous MED decreased both JA levels and the expression of JA-related genes. Infestation by viruliferous MED reduced plant JA levels. In preference tests, neither virus-free nor viruliferous MED discriminated among JA-varying plants previously exposed to virus-free MED. However, both virus-free and viruliferous MED preferred low-JA plant genotypes when choosing between plants that had both been previously exposed to viruliferous MED. The enhanced preference for low-JA genotypes appears linked to the volatile compound neophytadiene, which was found only in whitefly-infested plants and at concentrations inversely related to plant JA levels. Conclusions Our findings illustrate how plant defense can interact with prior herbivory to affect both a plant virus and its whitefly vector, and confirm the induction of neophytadiene by MED. The apparent attraction of MED to neophytadiene may prove useful in pest detection and management.

Apriona germari (Hope) presents a significant threat as a dangerous wood-boring pest, inflicting substantial harm to forest trees. Investigating the olfactory sensory system of A. germari holds substantial theoretical promise for developing eco-friendly control strategies. To date, however, the olfactory perception mechanism in A. germari remains largely unknown. Therefore, we performed transcriptome sequencing of A. germari across four distinct body parts: antennae, foreleg tarsal segments, mouthparts (maxillary and labial palps), and abdomen terminals, pinpointing the odorant binding protein (OBP) genes and analyzing their expression. We found eight AgerOBPs (5, 19, 23, 25, 29, 59, 63, 70) highly expressed in the antennae. In our competitive binding experiments, AgerOBP23 showed strong binding abilities to the pheromone component fuscumol acetate, eight plant volatiles (farnesol, cis -3-hexenal, nerolidol, myristol acetate, cis -3-hexenyl benzoate, (-)-α-cedrene, 3-ethylacetophenone, and decane), and four insecticides (chlorpyrifos, phoxim, indoxacarb, and cypermethrin). However, AgerOBP29 and AgerOBP63 did not show prominent binding activities to these tested chemicals. Through homology modeling and molecular docking, we identified the key amino acid sites involved in the binding process of AgerOBP23 to these ligands, which shed light on the molecular interactions underlying its binding specificity. Our study suggests that AgerOBP23 may serve as a potential target for future investigations of AgerOBP ligand binding. This approach is consistent with the reverse chemical ecology principle, establishing the groundwork for future studies focusing on attractant or repellent development by exploring further the molecular interactions between OBP and various compounds.

A simple model on volatile organic compound (VOC)-mediated plant–insect interactions is proposed and examined here, when two different classes of herbivorous insects competing for a common resource (plant) in the presence of a specialist carnivorous enemy, which only predates one of the herbivore species. We, particularly, emphasize the impact of VOCs on plant’s growth fitness. The system experiences several local and global bifurcations with emergent alternative states for variations in recruitment factors and predation rate. Basin transitions and basin of attractions have provided detail descriptions on the selectivity of the alternative states, when only one of the herbivore species can survive depending on the choice of initial population densities of the interacting species and how it provides a steady growth in plant. Additionally, our results support the concept of competitive exclusion principle in an indirect interspecific competition between the two herbivore types for the common resource, plant. [ABSTRACT FROM AUTHOR]

The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), is a common generalist predator in China and is occasionally found gathering on the Chinese pagoda tree, Sophora japonica, in summer. In a field investigation, we found that H. axyridis adults preferred S. japonica during its flowering period even though their optimal prey (aphid) is absent at this time. In addition, male and female adults were attracted to S. japonica flowers to a similar extent in a Y-tube olfactometer assay. Using coupled gas chromatography-electroantennogram detection (GC-EAD), we identified a flower odor component (nonanal) that elicited a significant electrophysiological response in H. axyridis. Electroantennogram (EAG) dose-dependent responses revealed that the amplitude of the adult beetle's EAG response increased with increasing concentration of nonanal, peaking at 10 mg mL−1. In Y-tube olfactometer behavioral tests, H. axyridis adults preferred a 10 mg mL−1 nonanal source over a 100 mg mL−1 diluent. Under field conditions, the adults were significantly attracted to both concentrations (10 and 100 mg mL−1), and high concentrations generally had greater attraction. All these results suggest that nonanal, a volatile compound of S. japonica flowers, greatly attracts H. axyridis adults. This study provides a basis for the development of synthetic attractants of H. axyridis, with the potential to promote biocontrol services of this generalist predator in the native area (e.g., China) and to suppress its population by mass trapping in its invasive areas.

Studies show that plant defenses influence the host‐use of herbivores and tend to be evolutionarily more labile than herbivore traits (e.g. feeding preferences). However, all previous studies have focused exclusively on non‐volatile plant defenses thereby overlooking the roles of plant volatiles.We hypothesized that volatiles are equally important determinants of herbivore host‐use and are evolutionarily more labile than herbivore traits. To test these hypotheses, the following experiments were conducted.We identified the volatiles and non‐volatiles of 17 Asteraceae species and measured their relative contents. We also used a highly resolved bipartite trophic network of the 17 host species and 20 herbivorous (pre‐dispersal seed predator) tephritid fly species to determine the evolutionary interactions between plants and herbivores.The chemical data showed that interspecific similarity in volatiles—but not non‐volatiles and phylogenetic distance—significantly accounted for the herbivore community across the plant species; this implies that plant volatiles—but not non‐volatile compounds and species identity—dictate plant‐tephritid fly interactions. Moreover, we observed phylogenetic signal for non‐volatiles but not for volatiles; therefore closely related herbivores do not necessarily use closely related host species with similar non‐volatiles, but do tend to attack plants producing similar volatiles. Thus, plant volatiles are evolutionarily more labile than non‐volatiles and herbivore traits associate with host use.These results show that the interactions between plants and herbivores are evolutionary asymmetric, shed light on the role of plant volatiles in plant–herbivore interactions, and highlight the need to include data for both volatiles and non‐volatiles when investigating plant–animal interactions. [ABSTRACT FROM AUTHOR]

Odorant receptors (ORs) are essential for plant–insect interactions. However, despite the global impacts of Lepidoptera (moths and butterflies) as major herbivores and pollinators, little functional data are available about Lepidoptera ORs involved in plant-volatile detection. Here, we initially characterized the plant-volatile-sensing function(s) of 44 ORs from the cotton bollworm Helicoverpa armigera , and subsequently conducted a large-scale comparative analysis that establishes how most orthologous ORs have functionally diverged among closely related species whereas some rare ORs are functionally conserved. Specifically, our systematic analysis of H. armigera ORs cataloged the wide functional scope of the H. armigera OR repertoire, and also showed that HarmOR42 and its Spodoptera littoralis ortholog are functionally conserved. Pursuing this, we characterized the HarmOR42-orthologous ORs from 11 species across the Glossata suborder and confirmed the HarmOR42 orthologs form a unique OR lineage that has undergone strong purifying selection in Glossata species and whose members are tuned with strong specificity to phenylacetaldehyde, a floral scent component common to most angiosperms. In vivo studies via HarmOR42 knockout support that HarmOR42-related ORs are essential for host-detection by sensing phenylacetaldehyde. Our work also supports that these ORs coevolved with the tube-like proboscis, and has maintained functional stability throughout the long-term coexistence of Lepidoptera with angiosperms. Thus, beyond providing a rich empirical resource for delineating the precise functions of H. armigera ORs, our results enable a comparative analysis of insect ORs that have apparently facilitated and currently sustain the intimate adaptations and ecological interactions among nectar feeding insects and flowering plants. [ABSTRACT FROM AUTHOR]

In nature, a plant can be infected by multiple viruses simultaneously. However, the effects of coinfection on plant–vector interactions are less well studied. Two begomoviruses of the family Geminiviridae, Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl China virus (TYLCCNV), occur sympatrically in China. Each of them is reported to increase the performance of whitefly vector via manipulation of plant traits. In this study, we examined the effects of coinfection by the two viruses TYLCV and TYLCCNV on plant–whitefly interactions, compared to that infected by a single virus. We found that plants infected by two viruses showed aggravated symptoms but the performance and preference of whiteflies were not altered significantly compared to singly-infected plants. Coinfection suppressed the transcription of genes involved in jasmonic acid (JA) signaling pathway in plants, but showed no significant difference to single-virus infected plants. These findings suggest that although TYLCV and TYLCCNV may synergistically induce plant symptoms, they did not manipulate synergistically plant-mediated responses to the insect vector. [ABSTRACT FROM AUTHOR]

Recently, there has been an increase in the number of reports that highlight the role of microbes and their volatile metabolites in interactions with plants and insects, including interactions which may benefit agricultural production. Accurate and reproducible volatile collection is crucial to investigations of chemical-mediated communication between organisms. Accordingly, accurate detection of volatiles emitted from microbe-inoculated media is a research priority. Though numerous classes of volatile organic compounds are emitted from plants, insects, and microbes, emissions from microbes typically contain polar compounds of high volatility. Therefore, commonly used plant or insect volatile collection techniques may not provide an accurate representation of microbe-specific volatile profiles. Here, we present and compare the volatile data derived via three solventless collection techniques: direct headspace injection, solid-phase microextraction (SPME), and active sampling with a sorptive matrix blend specifically designed to prevent collection filter breakthrough of VOCs (solid-phase extraction, SPE). These methods were applied to a synthetic floral nectar media containing a nectar-inhabiting yeast, Metschnikowia reukaufii, and sunflower (Helianthus annus) pollen. The yeast contributed alcohols, ketones, and esters, and the pollen provided terpenoids. Direct headspace injections were not effective, and the resultant chromatography was poor despite the use of on-column cryofocusing. SPME and SPE detected a similar number of volatiles, but with varying relative abundances. SPE collected a greater abundance of microbial volatiles than SPME, a difference driven by high ethanol capture in SPE. Both SPE and SPME are appropriate for analysis of microbial volatiles, though the sorbent type and amount, and other collection parameters should be further evaluated for each studied system.

Solid phase microextraction (SPME) has become a common technique for volatile sampling due to its ease of use and limited technical requirements. The solvent-free nature of SPME is also exceptionally attractive for gas chromatography mass spectrometry (GC/MS) analysis. To ensure efficient transfer of the sample to the GC, the manufacturer recommend injector desorption temperatures in the range of 200 to 320 °C. A high desorption temperature can, however, have unwanted effects on analyses of plant and insect produced semiochemicals. By investigating the quantitative and qualitative chromatographic responses at varying inlet temperatures for a component blend of seven plant produced volatile compounds, we found the thermally labile plant-nematode signaling compound, pregeijerene to degrade to geijerene at all tested temperatures within the recommended range (200, 240, and 280 °C), but that it did not break down with an inlet temperature below 200 °C (100 °C and 150 °C). Degradation was also detected for the sesquiterpene germacrene D, but only at the highest inlet temperature tested (280 °C). Surprisingly, an inlet temperature of 200 °C gave the highest sample recovery, measured as total peak area while an inlet temperature of 100 °C as well as 280 °C gave the lowest total area values. An increase in desorption time from 3 to 5 min. Resulted in a recovery at 100 °C close to that obtained at 200 °C. Peak broadening was minimal, and only observed at the 100 °C inlet temperature. Based on these results, we highly recommend that SPME users include desorption temperature as one variable when developing sampling procedures for novel biological systems to ensure that potentially present thermally labile compounds are not degraded. [ABSTRACT FROM AUTHOR]

Background: Most plant viruses rely on vectors for their transmission and spread. One of the outstanding biological questions concerning the vector-pathogen-symbiont multi-trophic interactions is the potential involvement of vector symbionts in the virus transmission process. Here, we used a multi-factorial system containing a non-persistent plant virus, cucumber mosaic virus (CMV), its primary vector, green peach aphid, Myzus persicae, and the obligate endosymbiont, Buchnera aphidicola to explore this uncharted territory. Results: Based on our preliminary research, we hypothesized that aphid endosymbiont B. aphidicola can facilitate CMV transmission by modulating plant volatile profiles. Gene expression analyses demonstrated that CMV infection reduced B. aphidicola abundance in M. persicae, in which lower abundance of B. aphidicola was associated with a preference shift in aphids from infected to healthy plants. Volatile profile analyses confirmed that feeding by aphids with lower B. aphidicola titers reduced the production of attractants, while increased the emission of deterrents. As a result, M. persicae changed their feeding preference from infected to healthy plants. Conclusions: We conclude that CMV infection reduces the B. aphidicola abundance in M. persicae. When viruliferous aphids feed on host plants, dynamic changes in obligate symbionts lead to a shift in plant volatiles from attraction to avoidance, thereby switching insect vector's feeding preference from infected to healthy plants. [ABSTRACT FROM AUTHOR]

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a key pest of sweet pepper cultivation, where it causes feeding damage, excretes phytotoxic substances, and transmits important viruses. Control with chemical insecticides often is ineffective because endophytic oviposition and the cryptic habits of the pest provide protection. In Uruguay, the biological control program of this pest in sweet pepper crops is at risk due to the low settlement rate and high dispersal of releases of predator Orius insidiosus (Say) (Hemiptera: Anthocoridae). Previous studies have ruled out an antibiosis effect as the cause of dispersal; therefore, we hypothesized antixenosis (non-preference) for the sweet pepper plants as the cause of poor biological control by O. insidiosus. The effect of olfactory stimuli from different structures of strawberry, corn, and sweet pepper plants (lamuyo and blocky type) on the behavior of O. insidiosus was evaluated in olfactometry and free-choice cage experiments. Since Orius tristicolor (White) (Hemiptera: Anthocoridae) occurs naturally in the area, it was included also in the study with the aim of assessing whether there are differences in behavior between the species. Orius tristicolor may act as a complementary biocontrol agent or competitor on sweet pepper. Y-tube experiments showed no preference for plant volatiles in any combination, and response to volatile stimuli generally was poor. However, in the free-choice cage experiment, females of both species of Orius preferred the flowering strawberry plants over the flowering sweet pepper plants, which could explain the low establishment of O. insidiosus when released on pepper with neighboring strawberry fields. Given that horticultural greenhouses in Uruguay and in many other countries are open, this information can be very useful in designing the spatial and temporal management of different crops on a production field, which enhances the effectiveness of these predatory species. [ABSTRACT FROM AUTHOR]

Insect Odorant-Binding Proteins (OBPs) play crucial roles in the discrimination, binding and transportation of odorants. Herein, the full-length cDNA sequence of Minus-C OBP1 (MaltOBP1) from the Japanese pine sawyer beetle, Monochamus alternatus, was cloned by 3′ and 5′ RACE-PCR and analyzed. The results showed that MaltOBP1 contains a 435 bp open reading frame (ORF) that encodes 144 amino acids, including a 21-amino acid signal peptide at the N-terminus. The matured MaltOBP1 protein possesses a predicted molecular weight of about 14 kDa and consists of six α-helices, creating an open binding pocket, and two disulfide bridges. Immunoblotting results showed that MaltOBP1 was most highly expressed in antennae in both sexes, followed by wings and legs. Fluorescence assays demonstrated that MaltOBP1 protein exhibited high binding affinity with (R)-(+)-α-pinene, (−)-β-pinene, trans-caryophyllene, (R)-(+)-limonene and (–)-verbenone, which are the main volatile compounds of the pine tree. Our combined results suggest that MaltOBP1 plays a role in host seeking behavior in M. alternatus.

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Aims: Plant volatiles serve as airborne semiochemicals, bridging the interactions between the plant and environment. Intercropping of a Chinese medicinal herb, Atractylodes lancea, with peanut plants greatly improves peanut growth, leading to a reduction of soil-borne disease. The underlying mechanism of peanut responding to the intercropped A. lancea is unknown. We here explored the response of the above- and belowground peanut parts to volatiles produced by the aboveground parts of A. lancea. Methods: Closed cultivation system was used. Composition of volatiles released by A. lancea plant was first determined using headspace solid phase microextraction–gas chromatography/mass spectrometry (SPME-GC-MS). Then, physiological responses of peanut were explored via enzymes activity assay and root secretions. Changes in the peanut rhizosphere fungal and bacterial communities were analyzed by Illumina sequencing. Results: The intercropped A. lancea volatiles induced a physiological response in peanut, which includes the increased catalase and phenylalanine ammonia lyase activity in peanut leaf, and improvement of peanut growth. Secretion of organic acids by the peanut root was increased in response to volatile treatment. Pyrosequencing of the whole internal transcribed spacer and 16S rRNA amplicons revealed significant differences in microbial diversity and composition in peanut rhizosphere upon volatile treatment. Conclusions: In the intercropping, A. lancea volatiles play a key role in influencing the growth of a neighbouring peanut plant, e.g., increasing biomass and affecting root colonization by soil microorganisms, which may increase plant protection against pathogens. Intercropping patterns could be designed accordingly to increase crop performance. [ABSTRACT FROM AUTHOR]

Mate finding in most moths is based on male perception of a female-emitted pheromone whose species specificity resides in component chemistry and proportions. Components are individually detected by specialized olfactory receptor neurons (ORNs) projecting into the macroglomerular complex (MGC) of the male brain. We asked how robust ratio recognition is when challenged by a plant volatile background. To test this, we investigated the perception of the pheromone blend in Agrotis ipsilon, a moth species whose females produce a blend of Z7-dodecenyl acetate (Z7-12:Ac), Z9-tetradecenyl acetate (Z9-14:Ac), and Z11-hexadecenyl acetate in a 4:1:4 ratio optimally attractive for males. First, we recorded the responses of specialist ORNs for Z7 and Z9 and showed that heptanal, a flower volatile, activated Z7 but not Z9 neurons. Then, we recorded intracellularly the responses of MGC neurons to various ratios and showed that heptanal altered ratio responses of pheromone-sensitive neurons. Finally, we analyzed the behavior of males in a wind tunnel and showed that their innate preference for the 4:1:4 blend was shifted in the presence of heptanal. Pheromone ratio recognition may thus be altered by background odorants. Therefore, the olfactory environment might be a selective force for the evolution of pheromone communication systems. [ABSTRACT FROM AUTHOR]

Copyright of Ege Üniversitesi Ziraat Fakültesi Dergisi is the property of Ege Universitesi, Ziraat Fakultesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Insect Odorant-Binding Proteins (OBPs) play crucial roles in the discrimination, binding and transportation of odorants. Herein, the full-length cDNA sequence of Minus-C OBP1 (MaltOBP1) from the Japanese pine sawyer beetle, Monochamus alternatus , was cloned by 3′ and 5′ RACE-PCR and analyzed. The results showed that MaltOBP1 contains a 435 bp open reading frame (ORF) that encodes 144 amino acids, including a 21-amino acid signal peptide at the N-terminus. The matured MaltOBP1 protein possesses a predicted molecular weight of about 14 kDa and consists of six α-helices, creating an open binding pocket, and two disulfide bridges. Immunoblotting results showed that MaltOBP1 was most highly expressed in antennae in both sexes, followed by wings and legs. Fluorescence assays demonstrated that MaltOBP1 protein exhibited high binding affinity with (R)-(+)-α-pinene, (−)-β-pinene, trans -caryophyllene, (R)-(+)-limonene and (–)-verbenone, which are the main volatile compounds of the pine tree. Our combined results suggest that MaltOBP1 plays a role in host seeking behavior in M. alternatus. [ABSTRACT FROM AUTHOR]

Background: While virus-vector-host interactions have been a major focus of both basic and applied ecological research, little is known about how different levels of plant defense interact with prior herbivory to affect these relationships. We used genetically-modified strains of tomato (Solanum lycopersicum) varying in the jasmonic acid (JA) plant defense pathways to explore how plant defense and prior herbivory affects a plant virus (tomato yellow leaf curl virus, 'TYLCV'), its vector (the whitefly Bemisia tabaci MED), and the host. Results: Virus-free MED preferred low-JA over high-JA plants and had lower fitness on high-JA plants. Viruliferous MED preferred low-JA plants but their survival was unaffected by JA levels. While virus-free MED did not lower plant JA levels, viruliferous MED decreased both JA levels and the expression of JA-related genes. Infestation by viruliferous MED reduced plant JA levels. In preference tests, neither virus-free nor viruliferous MED discriminated among JA-varying plants previously exposed to virus-free MED. However, both virus-free and viruliferous MED preferred low-JA plant genotypes when choosing between plants that had both been previously exposed to viruliferous MED. The enhanced preference for low-JA genotypes appears linked to the volatile compound neophytadiene, which was found only in whitefly-infested plants and at concentrations inversely related to plant JA levels. Conclusions: Our findings illustrate how plant defense can interact with prior herbivory to affect both a plant virus and its whitefly vector, and confirm the induction of neophytadiene by MED. The apparent attraction of MED to neophytadiene may prove useful in pest detection and management. [ABSTRACT FROM AUTHOR]

BACKGROUND Sitona weevils (Coleoptera: Curculionidae) are a species complex comprising pests of many leguminous crops worldwide, causing damage to young plants as adults and to rootlets as larvae, resulting in significant yield losses. Timely detection of migrating adult weevils is needed to determine when deployment of control measures becomes necessary. With the aim of developing plant volatile‐based lures for Sitona spp. detection, we investigated the responses of S. humeralis to host plant‐related aromatic compounds. RESULTS: In olfactometer studies, both male and female S. humeralis responded positively to the odour of alfalfa flowers, a source of aromatic volatiles. In single sensillum recordings, basiconic sensilla located on the third and fourth terminal segments of the antennal club of both sexes were found to respond to benzaldehyde at doses of 10−5 and 10−4 g, suggesting that the weevil is able to detect this compound at the peripheral sensory level. In field studies, S. humeralis was attracted to benzaldehyde in the spring, but not in the autumn. CONCLUSION: Benzaldehyde, as described in this study, may be a suitable candidate for the development of monitoring tools for S. humeralis. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Tritrophic interaction among host plant-herbivore-parasitoid involves chemical cues. The infested plant by herbivores has been reacted to produce volatiles which is a cue used by the herbivore parasitoids for host location. These volatiles can be developed to enhance natural control of insect pests, especially by optimally use of parasitoids. Egg parasitoids are biocontrol agents that play an important role in natural control of herbivores. This research used a tritrophic interaction model of rice plant-brown plant hopper (BPH)-egg parasitoid of BPH. Research on analysis of chemical cues in tritrophic interactions was aimed to identify volatiles that are used by the parasitoid to find its host. The volatiles that effectively affect the parasitoid orientation behavior could be developed into a parasitoid attractant. Extraction of volatiles as the egg parasitoid cues was done using soxhlet, and identification of the volatiles using Gas Chromatography-Mass Spectrometry (GC-MS). Bioassay of the volatiles on the BPH parasitoid orientation behavior was performed using Y-tube olfactometry. The volatiles that are used for host location cues by the parasitoid affect the parasitoid orientation behavior by showing the preference of the parasitoid females to the odor of volatile. Volatiles extracted from BPH-egg-infested plants and uninfested plants contain alcohol, hydrocarbon, and ester compounds. Based on the difference of the compound composition of both extractions, five compounds of long-chain hydrocarbon, both branched and unsaturated compounds are the main volatile components which caused positive orientation behavior of the egg parasitoid. The egg parasitoids showed positive behavior orientation toward the volatiles extracted from BPH-egg-infested plant. Those hydrocarbon compounds are potential materials to be developed into bio attractants of BPH egg parasitoid.

Camphor has been used as an effective repellent and pesticide to stored products for a long history, but Orthaga achatina (Lepidoptera: Pyralidae) has evolved to specifically feed on the camphor tree Cinnamomum camphora . However, the behavioral response of O. achatina to camphor and the molecular basis of camphor perception are totally unknown. Here, we demonstrated that both male and female adults were behaviorally attracted to camphor, suggesting the adaptation of O. achatina to and utilization of camphor as a signal of C. camphora . Second, in 40 O. achatina OR genes obtained by analyzing antenna transcriptomes, only OachOR16/Orco significantly responded to camphor in the Xenopus oocyte system. Finally, by molecular docking analysis and site-directed mutagenesis, the Ser209 residue is confirmed to be essential for binding of the oachOR16 with camphor. This study not only reveals the camphor-based host plant choice and olfactory mechanisms of O. achatina but also provides a molecular target for screening more potential insect repellents.

Phytocytokines mediate defense against pests and pathogens. Many methods have been developed to study the physiological responses triggered by phytocytokines in dicot plants. Here, we describe a detailed peptide feeding protocol to study the effect of phytocytokines on direct and indirect anti-herbivore defense in maize. This method relies on peptide uptake by the excised maize seedling or leaves via the transpiration stream. The headspace volatiles from plant samples are then analyzed by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), or by gas chromatography-mass spectrometry (GC-MS). The samples can also be further processed to evaluate phytocytokine-induced defense gene expression or phytohormone production., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Plants release an array of volatile chemicals into the air to communicate with other organisms in the environment. Insect attack triggers emission of herbivore-induced plant volatiles (HIPVs). How insect herbivores use these odors to plan their detoxification systems is vital for insect adaptation to environmental xenobiotics. Here we show that the larvae of Helicoverpa armigera (Hübner), a broadly polyphagous lepidopteran herbivore, have the capacity to use plant volatiles as cues to upregulate multiple detoxification systems, including cytochrome P450 monooxygenases (P450s), for detoxification of insecticides. Olfactory exposure of the fifth instars to two terpene volatiles limonene and nerolidol, and two green-leaf volatiles 2-heptanone and cis-3-hexenyl acetate significantly reduced larval susceptibility to the insecticide methomyl. However, larval pretreatment with piperonyl butoxide (PBO), a known P450 inhibitor, neutralized the effects of volatile exposure. Furthermore, larval exposure to the four plant volatiles enhanced activities of P450 enzymes in midguts and fatbodies, and upregulated expression of CYP6B2, CYP6B6 and CYP6B7, P450s involved in detoxification of the insecticide. Larval exposure to 2-heptanone and limonene volatiles also enhanced activities of glutathione-s-transferase and carboxylesterase. Our findings suggest that olfactory exposure to HIPVs enhances larval insecticide tolerance via induction of detoxification P450s.

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