4-Vinylanisole is an aggregation pheromone in locusts

Host–Pathogen Interactions between Metarhizium spp. and Locusts

The progress in research on the interactions between Metarhizium spp. and locusts has improved our understanding of the interactions between fungal infection and host immunity. A general network of immune responses has been constructed, and the pathways regulating fungal pathogenicity have also been explored in depth. However, there have been no systematic surveys of interaction between Metarhizium spp. and locusts. The pathogenesis of Metarhizium comprises conidial attachment, germination, appressorial formation, and colonization in the body cavity of the host locusts. Meanwhile, the locust resists fungal infection through humoral and cellular immunity. Here, we summarize the crucial pathways that regulate the pathogenesis of Metarhizium and host immune defense. Conidial hydrophobicity is mainly affected by the contents of hydrophobins and chitin. Appressorial formation is regulated by the pathways of MAPKs, cAMP/PKA, and Ca²⁺/calmodulin. Lipid droplets degradation and secreted enzymes contributed to fungal penetration. The humoral response of locust is coordinated by the Toll pathway and the ecdysone. The regulatory mechanism of hemocyte differentiation and migration is elusive. In addition, behavioral fever and density-dependent population immunity have an impact on the resistance of hosts against fungal infection. This review depicts a prospect to help us understand host–pathogen interactions and provides a foundation for the engineering of entomopathogenic fungi and the discovery of insecticidal targets to control insect pests.

Noninvasive examination of the cardiac properties of insect embryos enabled by optical coherence tomography

Understanding the cardiac properties of insect embryos at different development stages is important, however, few works have been conducted probably due to the lack of effective tools. Using locust embryos as an example, here we show, for the first time, that optical coherence tomography (OCT) is capable of obtaining detailed information of embryos' heart activities and irregularities, such as the heart rate, cardiac cycle, diastolic and systolic diameters, hemolymph pumping rate and ejection fraction at different stages of embryonic development and at different temperatures. We develop algorithms and mathematical methods for extracting and analyzing cardiac behavior information of locust embryos. We discover that locust embryos experienced suspended development (quiescence) caused by cold storage have a heart rate 20% more than that of embryos without experiencing quiescence and that the hemolymph pumping rate of the two types of embryos behaves differently as the embryos grow. In addition, using OCT as an accurate cardiac activity examination tool, we show that the heart rates of locust embryos are effectively reduced due to nitric oxide synthase gene silencing by RNA interference, indicating potential application of using locust embryos as a good model organism to study cardiovascular diseases, including the congenital heart disease and arrhythmia. Finally, the capabilities offered by OCT in the studies of locust embryonic development may also prove helpful to promote locust reproduction for nutritions or restrain locust reproduction for pest control.

The Entomopathogenic Fungus Metarhizium anisopliae Affects Feeding Preference of Sogatella furcifera and Its Potential Targets’ Identification

The rice planthopper Sogatella furcifera is a unique vector of the southern rice black-streaked dwarf virus (SRBSDV). The feeding behavior of S. furcifera should directly affect the diffusion of this virus. In this study, we noted that the infection of Metarhizium anisopliae CQMa421 on S. furcifera disturbed the feeding behavior of this pest to SRBSDV-infected rice, from preference to non-preference. Then, we further investigated the potential targets of M. anisopliae CQMa421 on the feeding behavior of S. furcifera after 0 h, 24 h and 48 h of infection by transcriptomic analysis via Illumina deep sequencing. A total of 93.27 GB of data was collected after sequencing, from which 91,125 unigenes were annotated, including 75 newly annotated genes. There were 1380 vs. 2187 and 137 vs. 106 upregulated and downregulated differentially expressed genes (DEGs) detected at 24 h and 48 h, respectively. The biological functions and associated metabolic processes of these genes were determined with the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The results suggested that major of DEGs are involved in energy metabolism, biosynthesis, immune response, the FoxO signaling pathway, the MAPK signaling pathway and apoptosis in response to the fungal infection. Noteworthily, several olfactory-related genes, including odorant receptors and odorant binding proteins, were screened from these differentially expressed genes, which played critical roles in regulating the olfactory behavior of insects. Taken together, these results provide new insights for understanding the molecular mechanisms underlying fungus and host insect interaction, especially for olfactory behavior regulated by fungus.

Odor-Induced Vomiting Is Combinatorially Triggered by Palp Olfactory Receptor Neurons That Project to the Lobus Glomerulatus in Locust Brain

Although vomiting is commonly recognized as a protective reaction in response to toxic stimuli, the elaborate sensory processes and necessary molecular components are not fully clear, which is due to a lack of appropriate experimental animal models. Vomiting reflex to volatile chemicals renders locust one candidate for vomiting model. Here, we identified a panel of chemical cues that evoked evident vomiting in locust nymphs and demonstrated the selected combinatorial coding strategy that palps but not antennae olfactory receptor neurons (ORNs) employed. Specifically, knocking down individual palp odorant receptors (ORs) such as OR17, OR21, and OR22 attenuated the vomiting intensity evoked by E-2-hexenal and hexanal, while suppression of OR12 and OR22 augmented vomiting to E-2-hexenal and 2-hexanone, respectively. Furthermore, dual-RNAi treatment against OR17 or OR21 together with OR22 resulted in a much lower response intensity than that of individual OR suppression. Furthermore, OR12 was revealed in palp sensilla basiconica (pb) subtype 3 to tune the neuronal decaying activity to E-2-hexenal. Finally, anterograde labeling indicated that palp ORNs primarily projected into the lobus glomerulatus (LG), and the projection neurons (PNs) in the LG further projected into the accessary calyx (ACA). Together, the establishment of an olfaction-inducible vomiting model in locusts deepens the understanding of olfactory coding logics and provides an opportunity to clarify the neural basis underlying animal vomiting.

Structural insights into the discrepant synergistic activity of Codlemone and (Z)-8-dodecenol towards Grapholita molesta pheromones

BACKGROUND

Insect pheromone synergists have been widely used to produce potent pheromone products for environment-friendly pest control. Codlemone (Cod) and (Z)-8-dodecenol (Dod) are two major Grapholita molesta pheromone synergists, with Cod having greater synergism and affinity for G. molesta pheromone binding protein 2 (GmolPBP2). Uncovering structural information key to the different binding affinity of Cod and Dod to GmolPBP2 would gain insights into what causes their synergy activity discrepancy.

RESULTS

Binding modes of the two synergists in the binding pocket of GmolPBP2 were analyzed and compared by molecular dynamics-based approaches. Although Cod and Dod were stabilized in a similar hydrophobic pocket, their interaction details with GmolPBP2 were divergent due to the extra double bond (C10═C11) in Cod. The C10═C11 improved the hydrophobic interactions of Cod with around residues. Such hydrophobic interaction improvement was also reflected in the raised importance of Phe11 in the GmolPBP2-Cod interaction. Not only that, the increased hydrophobic forces introduced by the C10═C11 changed the CH2-OH orientation in the GmolPBP2-Cod complex, which improved the H-bond interaction. Electrostatic complementarity analysis further indicated the positive role of C10═C11 in optimizing GmolPBP2-Cod interaction.

CONCLUSION

The C10═C11 is thought to contribute greatly to Cod's stronger synergy as a group key to the higher GmolPBP2-affinity, based on which the improvement directions for Cod and Dod were addressed as well. Our findings will aid in the development and optimization of more effective pheromone synergists, resulting in more effective pheromone-based pest management.

Cu-Catalyzed Dual C-O Bonds Cleavage of Cyclic Ethers with Carboxylic Acids, NaI, and TMSCF3 to Give Iodoalkyl Ester

Herein, by dual C-O bond cleavage of cyclic ethers with Cu catalysis, we eventually led to the development of a selective three-component coupling of commercially available chemicals, carboxylic acids, ethers, and halogens to synthesize more than 70 iodoalkyl esters in the presence of TMSCF₃. This allows for the concise synthesis of highly functionalized iodoalkyl esters directly. And the synthetic insect pheromones were also disclosed.

A nuclear receptor HR4 is essential for the formation of epidermal cuticle in the migratory locust, Locusta migratoria

Nuclear receptors (NRs) function as key factors in diverse signaling and metabolic pathways. Previous studies have focused on the roles of a nuclear receptor, hormone receptor 4 (HR4), mainly in holometabolous insects, while current knowledge of its function in hemimetabolous insects is still limited. In this study, we identified a HR4 gene in the orthopteran species Locusta migratoria. The full-length open reading frame of LmHR4 comprises 2694-nucleotides encoding a polypeptide of 897 amino acids, which contained a DNA-binding and a ligand-binding domain. Analyzing LmHR4 expression by quantitative reverse-transcription PCR (RT-qPCR) revealed that LmHR4 was highly expressed in integument, hindgut and fat body. During development from 3rd and 5th nymphal instars, the expression of LmHR4 reached maximal levels before ecdysis. We further demonstrated that LmHR4 expression is induced by 20-hydroxyecdysone (20E) and suppressed by silencing LmEcR, suggesting that LmHR4 expression is controlled by 20E signaling. The dsLmHR4-injected nymphs failed to molt and remained in the nymphal stage until death. Hematoxylin and eosin staining of the integument indicated that apolysis in the dsLmHR4-injected insects was delayed compared to that in control insects. Chitin staining and ultra-structural analysis showed that both the synthesis of the new cuticle and the degradation of the old cuticle were blocked in dsLmHR4-injected insects. Silencing LmHR4 decreased 20E titer and down-regulated the transcript levels of genes involved in chitin synthesis and degradation. Taken together, these results suggest that LmHR4 is essential for the formation of epidermal cuticle by mediating the 20E signaling to regulate the expression of chitin synthesis and degradation genes.

Genomics and genome editing techniques of crickets, an emerging model insect for biology and food science

Most tools available for manipulating gene function in insects have been developed for holometabolous species. In contrast, functional genetics tools for the Hemimetabola are highly underdeveloped. This is a barrier both to understanding ancestral insect biology, and to optimizing contemporary study and manipulation of particular large hemimetabolous orders of crucial economic and agricultural importance like the Orthoptera. For orthopteran insects, including crickets, the rapid spread of next-generation sequencing technology has made transcriptome data available for a wide variety of species over the past decade. Furthermore, whole genome sequences of orthopteran insects with relatively large genome sizes are now available. With these new genome assemblies and the development of genome editing technologies such as the CRISPR-Cas9 system, it has become possible to create gene knock-out and knock-in strains in orthopteran insects. As a result, orthopteran species should become increasingly feasible for laboratory study not only in research fields that have traditionally used insects, but also in agricultural fields that use them as food and feed. In this review, we summarize these recent advances and their relevance to such applications.

Aggregation pheromone 4-vinylanisole promotes the synchrony of sexual maturation in female locusts

Reproductive synchrony generally occurs in various group-living animals. However, the underlying mechanisms remain largely unexplored. The migratory locust, Locusta migratoria, a worldwide agricultural pest species, displays synchronous maturation and oviposition when forms huge swarm. The reproductive synchrony among group members is critical for the maintenance of locust swarms and population density of next generation. Here, we showed that gregarious female locusts displayed more synchronous sexual maturation and oviposition than solitarious females and olfactory deficiency mutants. Only the presence of gregarious male adults can stimulate sexual maturation synchrony of female adults. Of the volatiles emitted abundantly by gregarious male adults, the aggregation pheromone, 4-vinylanisole, was identified to play key role in inducing female sexual maturation synchrony. This maturation-accelerating effect of 4-vinylanisole disappeared in the females of Or35^-/- lines, the mutants of 4-vinylanisole receptor. Interestingly, 4-vinylanisole displayed a time window action by which mainly accelerates oocyte maturation of young females aged at middle developmental stages (3–4 days post adult eclosion). We further revealed that juvenile hormone/vitellogenin pathway mediated female sexual maturation triggered by 4-vinylanisole. Our results highlight a ‘catch-up’ strategy by which gregarious females synchronize their oocyte maturation and oviposition by time-dependent endocrinal response to 4-vinylanisole, and provide insight into reproductive synchrony induced by olfactory signal released by heterosexual conspecifics in a given group.

Since 2019, a plague of flying insects known as migratory locusts has been causing extensive damage to crops in East Africa. Migratory locusts sometimes live a solitary lifestyle but, if environmental conditions allow, they form large groups containing millions of individuals known as swarms that are responsible for causing locust plagues.Locusts are able to maintain such large swarms because they can aggregate and synchronize.

When they live in swarms, individual locusts produce odors that are sensed by other individuals in the group. For example, an aggregation pheromone, called 4-vinylanisole, is known to help keep large groups of locusts together. However, it is less clear how odors synchronize the reproductive cycles of the females in a swarm so that they are ready to mate with males and lay their eggs at the same time.

To address this question, Chen et al. examined when female locusts reached sexual maturity after they were exposed to odors produced by other locusts living alone or in groups. The experiments found that only 4-vinylanisole, which was abundantly released by adult male locusts living in groups, stimulated female locusts to reach sexual maturity at the same time. This odor increased the levels of a hormone known as juvenile hormone in less-developed females to help them reach sexual maturity sooner.

These findings demonstrate that when migratory locusts are living in swarms, male locusts promote the female locusts to reach sexual maturity at the same time by promoting less-developed females to ‘catch up’ with other females in the group. A next step will be to investigate the neural and molecular mechanisms underlying the ‘catch up’ effect induced by 4-vinylanisole.

Development of Botanical Pesticides: Exploration on the Phenotype of Vestigial Wings of Insect Pests Induced by Plant Natural Products or Their Derivatives by Blocking Tyrosine Phosphorylation of Insulin Receptor 1

Unlike faster-acting conventional insecticides, some botanical insecticides exhibit growth inhibitory activity against some insect pests. One of the distinguishing features of growth inhibitory activity appears to be in malformed moths with vestigial wings. However, the molecular mechanism underlying vestigial wings of insect pests induced by plant natural products or their derivatives is still elusive. In this work, based upon the phenotype of the vestigial wings of Mythimna separata Walker (as a model pest) induced by a podophyllotoxin derivative 2a (as a model compound), we found that compound 2a not only resulted in 22.1% of malformed moths with vestigial wings but also significantly decreased the fecundity of vestigial-winged female moths in the P generation; the trait of vestigial wings caused by 2a in the P generation can be inherited by the F1 generation; compound 2a may target insulin receptor 1 (InR1), suppress the InR1 mRNA level, and block InR1-pY1229 and InR1-pY1233/1234 phosphorylation levels in a tissue-specific manner "head/thorax/wing tissues". Notably, compound 2a can also induce the vestigial wings of Spodoptera frugiperda (another seriously harmful migratory lepidoptera pest). It is noteworthy that this insect insulin receptor can be used as a new kind of target receptors for the design of novel green insecticides.

Scanning Electron Microscopic Analysis of Antennal Sensilla and Tissue-Expression Profiles of Chemosensory Protein Genes in Ophraella communa (Coleoptera: Chrysomelidae)

Simple Summary

Leaf beetle Ophraella communa is considered an effective biocontrol agent against the common ragweed Ambrosia artemisiifolia. However, there are no studies that assess the antennal sensilla and chemosensory proteins expression profiles of O. communa. In this study, the types and morphology of sensilla on the antennae were examined by scanning electron microscopy (SEM). The results showed that there are six types of sensilla (sensilla trichodea, sensilla chaetica, sensilla basiconica, sensilla styloconica, sensilla coeloconica, and Böhm bristles) distributed on the antennae. We also found that the expression levels of five chemosensory proteins in male and female antennae were higher than those in other tissues by quantitative real-time polymerase chain reaction. Our results lay the foundation for interpreting the olfactory functions of adult O. communa.

Abstract

Ophraella communa is an efficient biocontrol agent used against the invasive weed Ambrosia artemisiifolia. It is an herbivorous insect that feeds on specific plants; the olfactory functions of this insects plays an important role in their search for host plants. There are no reports on O. communa sensilla types, morphology, or chemosensory protein (CSP) genes. In this study, we observed the external structure and distribution of antennal sensilla in adult O. communa antennae by scanning electron microscopy; moreover, we cloned 11 CSPs (CSP1–CSP11) and elucidated their tissue-expression profiles using quantitative real-time polymerase chain reaction. Six types of sensilla were identified: sensilla trichodea (including two subtypes), sensilla chaetica, sensilla basiconica (including two subtypes), sensilla styloconica, sensilla coeloconica, and Böhm bristles. Both male and female antennae had all six types of sensilla, and no sexual dimorphism was noted in sensillar types or distribution. We also found that the expression levels of CSP2, CSP3, CSP4, CSP6, and CSP7 in male and female antennae were higher than those in other tissues, which suggests that these five CSPs may be related to olfactory function in O. communa. Ultimately, our results lay the foundation for interpreting the olfactory functions of adult O. communa.

Effect of Soybean Volatiles on the Behavior of the Bean Bug, Riptortus pedestris

The bean bug, Riptortus pedestris, is a polyphagous insect that feeds primarily on leguminous plants, especially soybean (Glycine max). Although the bean bug is an economically important pest of soybean, little is known about how the insect locates soybean fields. In this study, we examined the electroantennogram responses of R. pedestris to soybean volatiles and examined the behavioral responses of the adult bean bugs. R. pedestris adults were attracted more to their host-plant soybean, even when physical contact was absent, than to air or a non-host plant. Accordingly, we hypothesized that R. pedestris can recognize soybean through a plant's volatile organic compounds (VOCs). Five VOCs were identified from intact soybean plants at the vegetative stage: (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 4-ethylbenzaldehyde, α-farnesene, and methyl salicylate. Response spectra of the antennae to these volatiles clearly showed that both male and female R. pedestris can detect soybean volatiles. The adult bean bugs did not show behavioral orientation to any individual compounds but showed significant orientation to a particular blend of synthetic soybean volatiles when tested under laboratory conditions. In the field, this soybean volatile blend did not significantly attract the bean bugs, but it did interact synergistically with the aggregation pheromone to attract the bean bugs. These results highlight the role of host plant volatiles in the sensory ecology of R. pedestris and help explain colonization pattern of the bean bugs in soybean fields.

A novel non-invasive identification of genome editing mutants from insect exuviae

With the wide application of genome editing in insects, a simple and efficient identification method is urgently needed to meet the increasing demand for mutation detection. Here, taking migratory locusts as a model system, we developed a non-invasive method to accurately identify genome-edited mutants by using DNA from insect exuviae. We compared the quantity and quality of genomic DNA from exuviae in five instar hoppers and found that the 1st instar exuviae had the highest DNA yield and content, while the 3rd instar exuviae had the best quality. Consensus genotypes were identified from genomic DNA of hoppers at different developmental stages in the same individuals. Moreover, we demonstrated that the amplification products from DNA extracted from locust exuviae are the consensus sequences with those from the hemolymph and foreleg pre-tarsus. Therefore, non-invasive samples provide the same genotyping results as minimally invasive and invasive samples of the same individuals. Furthermore, this identification method that uses genomic DNA from exuviae can be used for early screening of positive genome-edited individuals in each generation for adult crossing. In our study, the non-invasive identification method was not only simpler and provided results earlier than existing methods, but also had a better reproducibility and accuracy. This non-invasive identification approach using genomic DNA from exuviae can be adapted to meet the growing demand for genetic analysis and will find wide application in insect genome editing research.

Chemical Ecology and Olfaction in Short-Horned Grasshoppers (Orthoptera: Acrididae)

Chemoreception plays a crucial role in the reproduction and survival of insects, which often rely on their sense of smell and taste to find partners, suitable habitats, and food sources, and to avoid predators and noxious substances. There is a substantial body of work investigating the chemoreception and chemical ecology of Diptera (flies) and Lepidoptera (moths and butterflies); but less is known about the Orthoptera (grasshoppers, locusts, crickets, and wēta). Within the Orthoptera, the family Acrididae contains about 6700 species of short-horned grasshoppers. Grasshoppers are fascinating organisms to study due to their significant taxonomic and ecological divergence, however, most chemoreception and chemical ecology studies have focused on locusts because they are agricultural pests (e.g., Schistocerca gregaria and Locusta migratoria). Here we review studies of chemosensory systems and chemical ecology of all short-horned grasshoppers. Applications of genome editing tools and entomopathogenic microorganism to control locusts in association with their chemical ecology are also discussed. Finally, we identify gaps in the current knowledge and suggest topics of interest for future studies.

Alkyl-modified nucleobases with 6/5/7/5 ring systems from the insect Cyclopelta parva

(±)-Cyclopeltains A and B (1 and 2), two pairs of unusual alkylated adenine derivatives, were isolated from the insect Cyclopelta parva and structurally characterized.

Enterobacter hormaechei in the intestines of housefly larvae promotes host growth by inhibiting harmful intestinal bacteria

BACKGROUND

As a pervasive insect that transmits a variety of pathogens to humans and animals, the housefly has abundant and diverse microbial communities in its intestines. These gut microbes play an important role in the biology of insects and form a symbiotic relationship with the host insect. Alterations in the structure of the gut microbial community would affect larval development. Therefore, it is important to understand the mechanism regulating the influence of specific bacteria on the development of housefly larvae.

METHODS

For this study we selected the intestinal symbiotic bacterium Enterobacter hormaechei, which is beneficial to the growth and development of housefly larvae, and used it as a probiotic supplement in larval feed. 16S rRNA gene sequencing technology was used to explore the effect of E. hormaechei on the intestinal flora of housefly larvae, and plate confrontation experiments were performed to study the interaction between E. hormaechei and intestinal microorganisms.

RESULTS

The composition of the gut microflora of the larvae changed after the larvae were fed E. hormaechei, with the abundance of Pseudochrobactrum, Enterobacter and Vagococcus increasing and that of Klebsiella and Bacillus decreasing. Analysis of the structure and interaction of larval intestinal flora revealed that E. hormaechei inhibited the growth of harmful bacteria, such as Pseudomonas aeruginosa, Providencia stuartii and Providencia vermicola, and promoted the reproduction of beneficial bacteria.

CONCLUSIONS

Our study has explored the influence of specific beneficial bacteria on the intestinal flora of houseflies. The results of this study reveal the important role played by specific beneficial bacteria on the development of housefly larvae and provide insight for the development of sustained biological agents for housefly control through interference of gut microbiota.

Genetic and viral approaches to record or manipulate neurons in insects

The development of genetically encoded tools to record and manipulate neurons in vivo has greatly increased our understanding of how neuronal activity affects behavior. Recent advances enable the use of these tools in species not typically considered genetically tractable. This progress is revolutionizing neuroscience in general, and insect neuroethology in particular. Here we cover the latest innovations and some of their applications in phylogenetically diverse insect species. We discuss the importance and implications of these approaches for both basic and translational research. We focus on genetically encoded and virally encoded tools used for calcium imaging, optogenetics, and synaptic silencing. Finally, we discuss potential future developments of universally applicable, modular, and user-friendly genetic toolkits for neuroethological studies of insect behavior.

Old pesticide, new use: Smart and safe enantiomer of isocarbophos in locust control

Locust plagues are still worldwide problems. Selecting active enantiomers from current chiral insecticides is necessary for controlling locusts and mitigating the pesticide pollution in agricultural lands. Herein, two enantiomers of isocarbophos (ICP) were separated and the enantioselectivity in insecticidal activity against the pest Locusta migratoria manilensis (L. migratoria) and mechanisms were investigated. The significant difference of LD₅₀ between (+)-ICP (0.609 mg/kg bw) and (-)-ICP (79.412 mg/kg bw) demonstrated that (+)-ICP was a more effective enantiomer. The enantioselectivity in insecticidal activity of ICP enantiomers could be attributed to the selective affinity to acetylcholinesterase (AChE). Results of in vivo and in vitro assays suggested that AChE was more sensitive to (+)-ICP. In addition, molecular docking showed that the -CDOKER energies of (+)-ICP and (-)-ICP were 25.6652 and 24.4169, respectively, which suggested a stronger affinity between (+)-ICP and AChE. Significant selectivity also occurred in detoxifying enzymes activities (carboxylesterases (CarEs) and glutathione S-transferases (GSTs)) and related gene expressions. Suppression of detoxifying enzymes activities with (+)-ICP treatment suggested that (-)-ICP may induce the detoxifying enzyme-mediated ICP resistance. A more comprehensive understanding of the enantioselectivity of ICP is necessary for improving regulation and risk assessment of ICP.

Identification and field verification of an aggregation pheromone from the white-spotted flower chafer, Protaetia brevitarsis Lewis (Coleoptera: Scarabaeidae)

The white-spotted flower chafer (WSFC), Protaetia brevitarsis Lewis, is native to East Asia. Although their larvae are considered a potential resource insect for degrading plant residues, producing protein fodder, and processing to traditional medicine, adult WSFCs inflict damage to dozens of fruit and economic crops. The control of the WSFC still relies heavily on pesticides and the inefficient manual extraction of adults. Here, we report the identification and evaluation of the aggregation pheromone of WSFCs. From the headspace volatiles emitted from WSFC adults, anisole, 4-methylanisole, 2-heptanone and 2-nonanone were identified as WSFC-specific components. However, only anisole and 4-methylanisole elicited positive dose-response relationship in electroantennography tests, and only 4-methylanisole significantly attracted WSFCs of both sexes in olfactometer bioassays and field experiments. These results concluded that 4-methylanisole is the aggregation pheromone of WSFCs. Furthermore, we developed polyethylene vials as long-term dispensers of 4-methylanisole to attract and kill WSFCs. The polyethylene vial lures could effectively attracted WSFCs for more than four weeks. Pheromone-based lures can be developed as an environmentally friendly protocol for monitoring and controlling WSFC adults.

Density-dependent mating behaviors reduce male mating harassment in locusts

Male mating harassment may occur when females and males do not have the same mating objectives. Communal animals need to manage the costs of male mating harassment. Here, we demonstrate how desert locusts in dense populations reduce such conflicts through behaviors. In transient populations (of solitarious morphology but gregarious behavior), we found that nongravid females occupied separate sites far from males and were not mating, whereas males aggregated on open ground (leks), waiting for gravid females to enter the lekking sites. Once a male mounted a gravid female, no other males attacked the pair; mating pairs were thereby protected during the vulnerable time of oviposition. In comparison, solitarious locusts displayed a balanced sex ratio in low-density populations, and females mated irrespective of their ovarian state. Our results indicate that the mating behaviors of desert locusts are density dependent and that sex-biased behavioral group separation may minimize the costs of male mating harassment and competition.

Complete Genome Sequence of Weissella confusa LM1 and Comparative Genomic Analysis

The genus Weissella is attracting an increasing amount of attention because of its multiple functions and probiotic potential. In particular, the species Weissella confusa is known to have great potential in industrial applications and exhibits numerous biological functions. However, the knowledge on this bacterium in insects is not investigated. Here, we isolated and identified W. confusa as the dominant lactic acid bacteria in the gut of the migratory locust. We named this strain W. confusa LM1, which is the first genome of an insect-derived W. confusa strain with one complete chromosome and one complete plasmid. Among all W. confusa strains, W. confusa LM1 had the largest genome. Its genome was the closest to that of W. confusa 1001271B_151109_G12, a strain from human feces. Our results provided accurate evolutionary relationships of known Weissella species and W. confusa strains. Based on genomic analysis, the pan-genome of W. confusa is in an open state. Most strains of W. confusa had the unique genes, indicating that these strains can adapt to different ecological niches and organisms. However, the variation of strain-specific genes did represent significant correlations with their hosts and ecological niches. These strains were predicted to have low potential to produce secondary metabolites. Furthermore, no antibiotic resistance genes were identified. At the same time, virulence factors associated with toxin production and secretion system were not found, indicating that W. confusa strains were not sufficient to perform virulence. Our study facilitated the discovery of the functions of W. confusa LM1 in locust biology and their potential application to locust management.

Odor composition of field versus laboratory desert locust populations

Olfaction plays an important role in the behavioural ecology of the desert locust Schistocerca gregaria (Orthoptera:Acrididae). Different locust life stages and sexes use olfactory cues for different behaviours such as grouping, mating, oviposition, feeding, maturation and gregarization, which can be exploited for management of the desert locust. However, the full spectrum of the chemistry of volatiles released by the desert locust remains unknown. Here, we compared the volatile emissions of different life stages of a natural wild population reared in the laboratory for one generation with those of a population that has been reared in the laboratory for seven generations. Coupled gas chromatography-mass spectrometric analysis was used to identify captured volatiles. Analysis of similarities (ANOSIM) and non-metric multidimensional scaling of the volatile organic compounds (VOCs) showed significant chemo-diversity between different life stages, and sexes for the adults of the two populations. Additionally, chemical analysis showed that nymphs and adults of the field population released ~4- to 40-fold more volatiles, and they were compositionally richer than their laboratory counterparts. These results demonstrate the composition and variation in odors of field and laboratory populations of the desert locust, and that the discriminating odors warrant further investigation to determine their roles in the bioecology and management of this locust species.

A ras-related nuclear protein Ran participates in the 20E signaling pathway and is essential for the growth and development of Locusta migratoria

The small GTPase Ran is a member of the Ras superfamily of small GTP-binding proteins, which plays a key role in the translocation of RNA and proteins through the nuclear pore complex. In this study, the full-length cDNA sequence of LmRan gene was obtained, which consists of 648-nucleotides open reading frame (ORF) and encodes 215 amino acids. RT-qPCR results revealed that LmRan was expressed in all developmental days and tissues investigated. Injection of dsLmRan into 4th and 5th instar nymphs, resulted in a significant down-regulation of LmRan transcripts, respectively. All dsLmRan-injected nymphs died before molting. Further hematoxylin and eosin staining of the integument showed that there was no apolysis occurred after silencing LmRan. In addition, the weight of dsLmRan-injected nymphs was significantly lower than that of the control group, and the gastric caecum and midgut was severely smaller. Especiallly, the mRNA level of LmCYP302a1, LmCYP315a1 and LmCYP314a1 responsible for 20E synthesis, LmE75 and LmE74 genes involved in the 20E signaling pathway, LmGfat, LmUAP1 and LmCHT10 genes involved in chitin metabolism pathway were dramatically decreased in the dsLmRan-injected nymphs. Together, the results indicated that LmRan participate in the 20E signaling pathway, which is essential for the growth and development of locusts.

Observation of the fine structure of antennal sensilla of the stink bug, Eocanthecona furcellata (Hemiptera: Pentatomidae)

In order to explore the mechanism underlying chemosensation in Eocanthecona furcellata, the external morphology of its antennae and the type, quantity, distribution and ultrastructure of the sensilla were observed on both sexes of adults and 5th-instar nymphs using scanning electron microscopy. The results showed that the antennae of E. furcellata consisted of three parts: scape, pedicel and flagellum. There were five types of sensilla on the antennae, which included sensilla trichoidea (ST), sensilla chaetica (SCh), sensilla coeloconica (SCo), sensilla basiconica (SB) and squamifornia denticles (SD). Further, there were 4 subtypes of ST and SB and 2 subtypes of SCo and SCh. The number of sensilla on nymphs was significantly lower than that on adults. The antennae of adults showed sexual dimorphism, as the number of sensilla on female adults was higher than that on male adults. SB4 was found only on females and SCo2 was found only on males. These inter-sexual differences may be related to chemoreception of sex pheromone and chemical predation location. The morphology and putative functions of each sensilla were compared and discussed. These results provide a reference for further study of the behavioral biology, chemical ecology and electrophysiology of insects, and also provides a scientific basis for new ways of biological control.

Positive feedback amplification in swarming immune cell populations

Several immune cell types (neutrophils, eosinophils, T cells, and innate-like lymphocytes) display coordinated migration patterns when a population, formed of individually responding cells, moves through inflamed or infected tissues. "Swarming" refers to the process in which a population of migrating leukocytes switches from random motility to highly directed chemotaxis to form local cell clusters. Positive feedback amplification underlies this behavior and results from intercellular communication in the immune cell population. We here highlight recent findings on neutrophil swarming from mouse models, zebrafish larvae, and in vitro platforms for human cells, which together advanced our understanding of the principles and molecular mechanisms that shape immune cell swarming.

Neutrophils self-limit swarming to contain bacterial growth in vivo

Neutrophils communicate with each other to form swarms in infected organs. Coordination of this population response is critical for the elimination of bacteria and fungi. Using transgenic mice, we found that neutrophils have evolved an intrinsic mechanism to self-limit swarming and avoid uncontrolled aggregation during inflammation. G protein-coupled receptor (GPCR) desensitization acts as a negative feedback control to stop migration of neutrophils when they sense high concentrations of self-secreted attractants that initially amplify swarming. Interference with this process allows neutrophils to scan larger tissue areas for microbes. Unexpectedly, this does not benefit bacterial clearance as containment of proliferating bacteria by neutrophil clusters becomes impeded. Our data reveal how autosignaling stops self-organized swarming behavior and how the finely tuned balance of neutrophil chemotaxis and arrest counteracts bacterial escape.

CRISPR/Cas9 mediated knockout of Amyellow-y gene results in melanization defect of the cuticle in adult Apis mellifera

Visible genetic markers are critical to gene function studies using genome editing technology in insects. However, there is no report about visible phenotypic markers in Apis mellifera, which extremely influences the application of genomic editing in honey bees. Here, we cloned and characterized the Amyellow-y gene in A. mellifera. Stage expression profiles showed that Amyellow-y gene was highly expressed in 2-, 4-day-old pupae, and newly emerged bees, and a high expression level was detected in the leg, thorax, wing and sting. To understand its functional role in pigmentation, Amyellow-y edited honeybees were created using CRISPR/Cas9, and it was found that the black pigment was decreased in the cuticle of mosaic workers and mutant drones. In particular, mutant drones manifested an overall appearance of yellowish cuticle in the body and appendages, including antennae, wings and legs, indicating that mutagenesis induced by disruption of Amyellow-y with CRISPR/Cas9 are heritable. Furthermore, the expression levels of genes associated with melanin pigmentation was investigated in mutant and wild-type drones using quantitative reverse transcription PCR. Transcription levels of Amyellow-y and aaNAT decreased markedly in mutant drones than that in wild-type ones, whereas laccase 2 was significantly up-regulated. Our results provide the first evidence, to our knowledge, that CRISPR/Cas9 edited G1 mutant drones of A. mellifera have a dramatic body pigmentation defect that can be visualized in adults, suggesting that Amyellow-y may serve as a promising visible phenotypic marker for genome editing in honey bees.

Functional Characterization of a Candidate Sex Pheromone Receptor AlinOR33 Involved in the Chemoreception of Adelphocoris lineolatus

Sex pheromones are deemed to play a significant role in sexual communication of most insects. Although many sex pheromone components in mirid bugs have been identified, the roles of odorant receptors in sex pheromone perception in Adelphocoris spp. (Hemiptera: Miridae) remain unknown so far. Here, AlinOR33, a candidate sex pheromone receptor in Adelphocoris lineolatus was functionally characterized. Phylogenetic analysis showed that AlinOR33 clustered with the sex pheromone receptor AlucOR4 fromApolygus lucorum. Quantitative real-time PCR measurement revealed that the expression of AlinOR33 increased gradually from nymph to adult stage and reached its peak in the antennae of 3-day-old mated male bugs. The subsequent in situ hybridization demonstrated that AlinOR33 was mainly expressed in sensilla trichoid on the antennae of A. lineolatus. In the two-electrode voltage clamp recordings, AlinOR33/AlinOrco was specifically tuned to four sex pheromone components including butyl butyrate, hexyl hexanoate, trans-2-hexenyl butyrate and hexyl butyrate, and especially most sensitive to the major component trans-2-hexenyl butyrate. After dsAlinOR33 injection, the electroantennogram responses of males to four sex pheromone components were reduced significantly (∼50%). Compared to control bugs, dsAlinOR33-injected male bugs almost lost behavioral preference for trans-2-hexenyl butyrate. Furthermore, the wingbeat frequency of dsAlinOR33-injected male bugs notably declined. Therefore, we conclude that as a candidate sex pheromone receptor, AlinOR33 plays essential roles in the sexual behavior of A. lineolatus.

The promises and challenges of archiving insect behavior and natural history in a changing world

Insect behavioral ecologists are not routinely archiving their behavioral media files and natural history observations. This is especially problematic because most behaviors are not preserved by the physical specimens stored in typical natural history collections. Improving the reporting and archiving of insect behavior and natural history data holds the promise of allowing scientists to track real-time responses of animals to global change and will preserve aspects of natural history that might otherwise be lost due to extinctions. Here we argue that behavioral ecologists should work to preserve and archive raw media files and field notes related to behavior and natural history of their study organisms. One major mechanism to incentivize archiving of such data would be for journals to develop policies for archiving of natural history data that is the focus of the paper or ancillary information collected about study subjects. Buy in from researchers, journals, and funding agencies will be needed to make substantial changes in data archiving.

Cholinergic calcium responses in cultured antennal lobe neurons of the migratory locust

Locusts are advantageous organisms to elucidate mechanisms of olfactory coding at the systems level. Sensory input is provided by the olfactory receptor neurons of the antenna, which send their axons into the antennal lobe. So far, cellular properties of neurons isolated from the circuitry of the olfactory system, such as transmitter-induced calcium responses, have not been studied. Biochemical and immunocytochemical investigations have provided evidence for acetylcholine as classical transmitter of olfactory receptor neurons. Here, we characterize cell cultured projection and local interneurons of the antennal lobe by cytosolic calcium imaging to cholinergic stimulation. We bulk loaded the indicator dye Cal-520 AM in dissociated culture and recorded calcium transients after applying cholinergic agonists and antagonists. The majority of projection and local neurons respond with increases in calcium levels to activation of both nicotinic and muscarinic receptors. In local interneurons, we reveal interactions lasting over minutes between intracellular signaling pathways, mediated by muscarinic and nicotinic receptor stimulation. The present investigation is pioneer in showing that Cal-520 AM readily loads Locusta migratoria neurons, making it a valuable tool for future research in locust neurophysiology, neuropharmacology, and neurodevelopment.

One hundred years of phase polymorphism research in locusts

One hundred years ago in 1921, Sir Boris Uvarov recognized that two locust species are one species but appearing in two different phases, a solitarious and a gregarious phase. As locust swarms are still a big problem affecting millions of people, basic research has tried to understand the causes for the transition between phases. This phenomenon of phase polymorphism, now called polyphenism, is a very complex multifactorial process and this short review will draw attention to this important aspect of insect research.

Morphology and Distribution of Antennal Sensilla in Three Species of Thripidae (Thysanoptera) Infesting Alfalfa Medicago sativa

Thrips are important pests to alfalfa Medicago sativa. Similar as many other plant-feeding insects, thrips rely on the antennae to receive chemical signals in the environment to locate their hosts. Previous studies indicated that sensilla of different shapes on the surface of insect antenna play an important role in signal recognition. However, morphological analysis of the antennal sensilla in Thysanoptera has been limited to only a few species. To expand the understanding of how antennal sensilla are related to semiochemical detection in thrips, here we compared the morphology and distribution of antennal sensilla in three thrip species, Odontothrips loti, Megalurothrips distalis, and Sericothrips kaszabi, by scanning electron microscope (SEM). The antennae of these three species are all composed of eight segments and share similar types of sensilla which distribute similarly in each segment, despite that their numbers show sexual dimorphism. Specifically, nine major types of sensilla in total were found, including three types of sensilla basiconica (SBI, SBII, and SBIII), two types of sensilla chaetica (SChI and SChII), and one type for each of sensilla coeloconica (SCo), sensilla trichodea (ST), sensilla campaniformia (SCa), and sensilla cavity (SCav). The potential functions of sensilla were discussed according to the previous research results and will lay a morphological foundation for the study of the olfactory mechanism of three species of thrips.

Insect alarm pheromones in response to predators: Ecological trade-offs and molecular mechanisms

Insect alarm pheromones are chemical substances that are synthesized and released in response to predators to reduce predation risk. Alarm pheromones can also be perceived by predators, who take advantage of alarm cues to locate prey. While selection favors evolution of alarm pheromone signals that are not easily detectable by predators, predator evolution selects for better prey detection ability. Here, we review the diversity of alarm signals, and consider the behavioral and ecological conditions under which they have evolved. We show that components of alarm pheromones are similar across many insects, although aphids exhibit different behavioral responses to alarm cues compared to social insects. The effects of alarm pheromones on prey behavior depend on factors such as the concentration of pheromones and the density of conspecifics. We also discuss the molecular mechanisms of alarm pheromone perception underlying the evolutionary arms race between predators and prey, and the function of olfactory proteins and receptors in particular. Our review provides a novel synthesis of the diversity and function of insect alarm pheromones, while suggesting avenues that might better allow researchers to exploit population-level responses to alarm signaling for the sustainable management of pests and vector-borne pathogens.