The grasshopper genome reveals long-term gene content conservation of the X Chromosome and temporal variation in X Chromosome evolution.

We present the first chromosome-level genome assembly of the grasshopper, Locusta migratoria, one of the largest insect genomes. We use coverage differences between females (XX) and males (X0) to identify the X Chromosome gene content, and find that the X Chromosome shows both complete dosage compensation in somatic tissues and an underrepresentation of testis-expressed genes. X-linked gene content from L. migratoria is highly conserved across seven insect orders, namely Orthoptera, Odonata, Phasmatodea, Hemiptera, Neuroptera, Coleoptera, and Diptera, and the 800 Mb grasshopper X Chromosome is homologous to the fly ancestral X Chromosome despite 400 million years of divergence, suggesting either repeated origin of sex chromosomes with highly similar gene content, or long-term conservation of the X Chromosome. We use this broad conservation of the X Chromosome to test for temporal dynamics to Fast-X evolution, and find evidence of a recent burst evolution for new X-linked genes in contrast to slow evolution of X-conserved genes.

Gene gain and loss from the Asian corn borer W chromosome.

BACKGROUND: Sex-limited chromosomes Y and W share some characteristics, including the degeneration of protein-coding genes, enrichment of repetitive elements, and heterochromatin. However, although many studies have suggested that Y chromosomes retain genes related to male function, far less is known about W chromosomes and whether they retain genes related to female-specific function. RESULTS: Here, we built a chromosome-level genome assembly of the Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Crambidae, Pyraloidea), an economically important pest in corn, from a female, including both the Z and W chromosome. Despite deep conservation of the Z chromosome across Lepidoptera, our chromosome-level W assembly reveals little conservation with available W chromosome sequence in related species or with the Z chromosome, consistent with a non-canonical origin of the W chromosome. The W chromosome has accumulated significant repetitive elements and experienced rapid gene gain from the remainder of the genome, with most genes exhibiting pseudogenization after duplication to the W. The genes that retain significant expression are largely enriched for functions in DNA recombination, the nucleosome, chromatin, and DNA binding, likely related to meiotic and mitotic processes within the female gonad. CONCLUSIONS: Overall, our chromosome-level genome assembly supports the non-canonical origin of the W chromosome in O. furnacalis, which experienced rapid gene gain and loss, with the retention of genes related to female-specific function.

Antennal Transcriptome Analysis of Olfactory Genes and Characterization of Odorant Binding Proteins in Odontothrips loti (Thysanoptera: Thripidae).

To identify odors in complex environments accurately, insects have evolved multiple olfactory proteins. In our study, various olfactory proteins of Odontothrips loti Haliday, an oligophagous pest that primarily affects Medicago sativa (alfalfa), were explored. Specifically, 47 putative olfactory candidate genes were identified in the antennae transcriptome of O. loti, including seven odorant-binding proteins (OBPs), nine chemosensory proteins (CSPs), seven sensory neuron membrane proteins (SNMPs), eight odorant receptors (ORs), and sixteen ionotropic receptors (IRs). PCR analysis further confirmed that 43 out of 47 genes existed in O. loti adults, and O.lotOBP1, O.lotOBP4, and O.lotOBP6 were specifically expressed in the antennae with a male-biased expression pattern. In addition, both the fluorescence competitive binding assay and molecular docking showed that p-Menth-8-en-2-one, a component of the volatiles of the host, had strong binding ability to the O.lotOBP6 protein. Behavioral experiments showed that this component has a significant attraction to both female and male adults, indicating that O.lotOBP6 plays a role in host location. Furthermore, molecular docking reveals potential active sites in O.lotOBP6 that interact with most of the tested volatiles. Our results provide insights into the mechanism of O. loti odor-evoked behavior and the development of a highly specific and sustainable approach for thrip management.

Genome-Wide Scans and Transcriptomic Analyses Characterize Selective Changes as a Result of Chlorantraniliprole Resistance in Plutella xylostella.

Pesticide resistance in insects is an example of adaptive evolution occurring in pest species and is driven by the artificial introduction of pesticides. The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), has evolved resistance to various insecticides. Understanding the genetic changes underpinning the resistance to pesticides is necessary for the implementation of pest control measures. We sequenced the genome of six resistant and six susceptible DBM individuals separately and inferred the genomic regions of greatest divergence between strains using FST and θπ. Among several genomic regions potentially related to insecticide resistance, CYP6B6-like was observed with significant divergence between the resistant and susceptible strains, with a missense mutation located near the substrate recognition site (SRS) and four SNPs in the promoter. To characterize the relative effects of directional selection via insecticide tolerance ('strain') as compared to acute exposure to insecticide ('treatment'), four pairwise comparisons were carried out between libraries to determine the differentially expressed genes. Most resistance-related differentially expressed genes were identified from the comparison of the strains and enriched in pathways for exogenous detoxification including cytochrome P450 and the ABC transporter. Further confirmation came from the weighted gene co-expression network analysis, which indicated that genes in the significant module associated with chlorantraniliprole resistance were enriched in pathways for exogenous detoxification, and that CYP6B6-like represented a hub gene in the "darkred" module. Furthermore, RNAi knock-down of CYP6B6-like increases P. xylostella sensitivity to chlorantraniliprole. Our study thus provides a genetic foundation underlying selection for pesticide resistance and plausible mechanisms to explain fast evolved adaptation through genomic divergence and altered gene expression in insects.

RNA-seq reveals plant virus composition and diversity in alfalfa, thrips, and aphids in Beijing, China.

Viruses are widespread in alfalfa (Medicago sativa L.), representing a key limitation to the production of this important forage plant. Understanding the diversity of plant viruses in alfalfa and their potential vectors will play an important role in management to minimize the emergence, transmission, and impact of viruses. Next-generation sequencing (NGS) targeting the transcriptome was applied to monitor the virus communities in alfalfa and its two main pests, thrips (Odontothrips loti Haliday and Frankliniella intonsa Trybom) and aphids (Acyrthosiphon pisum Mordvilko and Therioaphis trifolii Monell). A comparison of transcriptome datasets with reference databases revealed the presence of eight candidate viruses. Five out of the eight viruses, alfalfa mosaic virus (AMV), Medicago sativa alphapartitivirus 1 (MsAPV1), Medicago sativa deltapartitivirus 1 (MsDPV1), Medicago sativa amalgavirus 1 (MsAV1), and bean yellow mosaic virus (BYMV), were confirmed by RT-PCR. We identified and determined the presence of four RNA viruses from alfalfa samples, two viruses (AMV and MsAPV1) from thrips samples, and one virus (BYMV) from T. trifolii. All sequences isolated from the insect samples were more than 95% identical to the sequences from the alfalfa samples or to sequences from the National Center for Biotechnology Information (NCBI) reference database. The RNA-seq results of this study suggest that AMV and MsAPV1 are the predominant RNA plant viruses infecting alfalfa and that they are carried by the major pests. This lays the foundation for future research on the vectors and transmission of these viruses. In addition, the sequence data have enabled the assembly of the first complete genome sequence of MsDPV1 from alfalfa.

Illumina Sequencing of 18S/16S rRNA Reveals Microbial Community Composition, Diversity, and Potential Pathogens in 17 Turfgrass Seeds.

The increasing need for turfgrass seeds is coupled with the high risk of dangerous microbial pathogens being transmitted through the domestic and international trade of seeds. Concerns continue to be raised about seed safety and quality. Here, we show that next-generation sequencing (NGS) of DNA represents an effective and reliable tactic to monitor the microbial communities within turfgrass seeds. A comparison of DNA sequence data with reference databases revealed the presence of 26 different fungal orders. Among them, serious plant disease pathogens such as Bipolaris sorokiniana, Boeremia exigua, Claviceps purpurea, and Rhizoctonia zeae were detected. Seedborne bacteria, including Erwinia persicina and Acidovorax avenae, were identified from different bacterial orders. Our study indicated that the traditional culturing method and the NGS approach for pathogen identification complement each other. The reliability of culturing and NGS methods was further validated by PCR with specific primers. The combination of these different techniques ensures maximum sensitivity and specificity for turfgrass seed pathogen testing assay.

A genome-wide association study explores the genetic determinism of host resistance to Salmonella pullorum infection in chickens.

BACKGROUND: Salmonella infection is a serious concern in poultry farming because of its impact on both economic loss and human health. Chicks aged 20 days or less are extremely vulnerable to Salmonella pullorum (SP), which causes high mortality. Furthermore, an outbreak of SP infection can result in a considerable number of carriers that become potential transmitters, thus, threatening fellow chickens and offspring. In this study, we conducted a genome-wide association study (GWAS) to detect potential genomic loci and candidate genes associated with two disease-related traits: death and carrier state. METHODS: In total, 818 birds were phenotyped for death and carrier state traits through a SP challenge experiment, and genotyped by using a 600 K high-density single nucleotide polymorphism (SNP) array. A GWAS using a single-marker linear mixed model was performed with the GEMMA software. RNA-sequencing on spleen samples was carried out for further identification of candidate genes. RESULTS: We detected a region that was located between 33.48 and 34.03 Mb on chicken chromosome 4 and was significantly associated with death, with the most significant SNP (rs314483802) accounting for 11.73% of the phenotypic variation. Two candidate genes, FBXW7 and LRBA, were identified as the most promising genes involved in resistance to SP. The expression levels of FBXW7 and LRBA were significantly downregulated after SP infection, which suggests that they may have a role in controlling SP infections. Two other significant loci and related genes (TRAF3 and gga-mir-489) were associated with carrier state, which indicates a different polygenic determinism compared with that of death. In addition, genomic inbreeding coefficients showed no correlation with resistance to SP within each breed in our study. CONCLUSIONS: The results of this GWAS with a carefully organized Salmonella challenge experiment represent an important milestone in understanding the genetics of infectious disease resistance, offer a theoretical basis for breeding SP-resistant chicken lines using marker-assisted selection, and provide new information for salmonellosis research in humans and other animals.

An aquaporin protein is associated with drought stress tolerance.

Water channel proteins known as aquaporins (AQPs) regulate the movement of water and other small molecules across plant vacuolar and plasma membranes; they are associated with plant tolerance of biotic and abiotic stresses. In this study, a PIP type AQPs gene, designated as GoPIP1, was cloned from Galega orientalis, a high value leguminous forage crop. The GoPIP1 gene consists of an 870 bp open reading frame encoding a protein of 289 amino acids, and belongs to the PIP1 subgroup of the PIP subfamily. The transcript level of GoPIP1 was higher in the root of G. orientalis than in the leaf and stem. The level of GoPIP1 transcript increased significantly when treated with 200 mM NaCl or 20% polyethylene glycol (PEG) 6000. Transient expression of GoPIP1 in onion epidermal cells revealed that the GoPIP1 protein was localized to the plasma membrane. Over-expression of GoPIP1 increased the rosette/root ratio and increased sensitivity to drought in transgenic Arabidopsis plants. However, GoPIP1 over-expression in Arabidopsis had no significant effect under saline condition. The present data provides a gene resource that contributes to furthering our understanding of water channel protein and their application in plant stress tolerance.

Transmission from seed to seedling and elimination of alfalfa viruses.

Introduction: Viral diseases have become a vital factor limiting the development of the alfalfa (Medicago sativa) industry. Six viruses infecting alfalfa with a high incidence rate are Alfalfa mosaic virus (AMV), Medicago sativa alphapartitivirus 1 (MsAPV1), Medicago sativa alphapartitivirus 2 (MsAPV2), Medicago sativa deltapartitivirus 1 (MsDPV1), Medicago sativa amalgavirus 1 (MsAV1), and Cnidium vein yellowing virus 1 (CnVYV1). The purpose of this study was to develop preventive measures against these viruses by investigating their transmission through alfalfa seeds. Methods: In this study, we investigated the transmission rate of alfalfa viruses from seed to seedling by PCR, determined the location of viruses in seed by dissecting seed embryos and seed coat, tracked the changes of viruses in seedlings, and finally discover effective elimination measures for alfalfa viruses from 16 measures. Results and discussion: Our results demonstrated that all these six viruses could be transmitted from alfalfa seeds to seedlings with the transmission rate ranging from 44.44% to 88.89%. For AMV, MsAPV2, and MsAV1, the viral load was significantly higher in the seed coats than in the seed embryos; however, it did not show significant differences between these two parts of the seeds for MsAPV1, MsDPV1, and CnVYV1. Dynamic accumulation analysis of AMV and MsAPV2 indicated that the viral load in plants increased continuously in the early growth stage, making it important to inactivate these viruses prior to their seed-to-seedling transmission. Sixteen treatments including physical, chemical, and combinations of physical and chemical measures were compared in terms of their elimination efficiency on AMV and MsAPV2 and impacts on seed germination. The results showed that soaking alfalfa seeds in sterile distilled water for 2h + 2% NaClO for 1h or 2% NaClO for 1h were more promisingly applicable because it could significantly reduce AMV and MsAPV2 particles in both seeds and seedlings. Our data revealed a route of virus transmission in alfalfa and shed light on the discovery of a highly efficient method for the management of alfalfa viral diseases.

Identification of pheromone-like compounds in male reproductive organs of the oriental locust Locusta migratoria.

Despite the great economical interest of locusts in agriculture, knowledge on their chemoreception systems is still poor. Phenylacetonitrile is recognised as a pheromone of the desert locust Schistocerca gregaria, triggering gregarization, promoting aggregation and inhibiting courtship. However, in the other major locust species, Locusta migratoria, pheromones have not been reported. We have identified the two isomers of naphthylpropionitrile from the male reproductive organs of L. migratoria. Chemical synthesis has confirmed the identity of the two compounds. Both isomers show significant affinity to CSP91, a protein reported in the testis, but not to three other proteins of the same family (CSP180, CSP540 and CSP884) expressed in female accessory glands. The striking similarity of these compounds with phenylacetonitrile and the unusual nature of such chemicals strongly suggest that naphthylpropionitrile could be pheromones for L. migratoria, while their site of expression and binding activity indicate a role in communication between sexes.

Diversity, abundance, and sex-specific expression of chemosensory proteins in the reproductive organs of the locust Locusta migratoria manilensis.

Chemosensory proteins (CSPs) are small soluble proteins often associated with chemosensory organs in insects but include members involved in other functions, such as pheromone delivery and development. Although the CSPs of the sensory organs have been extensively studied, little is known on their functions in other parts of the body. A first screening of the available databases has identified 70 sequences encoding CSPs in the oriental locust Locusta migratoria manilensis. Applying proteomic analysis, we have identified 17 of them abundantly expressed in the female reproductive organs, but only one (CSP91) in male organs. Bacterially expressed CSP91 binds fatty acids with a specificity for oleic and linoleic acid, as well as medium-length alcohols and esters. The same acids have been detected as the main gas chromatographic peaks in the dichloromethane extracts of reproductive organs of both sexes. The abundance and the number of CSPs in female reproductive organs indicates important roles for these proteins. We cannot exclude that different functions can be associated with each of the 17 CSPs, including delivery of semiochemicals, solubilization of hormones, direct control of development, or other unknown tasks.

Immunolocalization of odorant-binding proteins on antennal chemosensilla of the peach aphid Myzus persicae (Sulzer).

The antennal sensilla of Myzus persicae were mapped using scanning and transmission electron microscopy. Placoid sensilla and coeloconic sensilla were found on the 6th segments, whereas 2 types of trichoid sensilla were present all through the length of the antenna. A single sensillum placoideum was located on the 5th segment, whereas alate aphids also presented placoid sensilla on the 3rd antennal segment. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of antennal chemosensilla. The antiserum against OBP7 intensively labeled all placoid sensilla from both primary and secondary rhinaria, with gold granules concentrated in the lymph surrounding the dendrite. OBP6 and OBP3 could also be detected in placoid sensilla, but less strongly than OBP7. Barely significant reaction or no reaction was observed with antibodies against OBP8.

Identification of CNGCs in Glycine max and Screening of Related Resistance Genes after Fusarium solani Infection.

Cyclic nucleotide-gated channels (CNGCs), non-selective cation channels localised on the plasmalemma, are involved in growth, development, and regulatory mechanisms in plants during adverse stress. To date, CNGC gene families in multiple crops have been identified and analysed. However, there have been no systematic studies on the evolution and development of CNGC gene families in legumes. Therefore, in the present study, via transcriptome analysis, we identified 143 CNGC genes in legumes, and thereafter, classified and named them according to the grouping method used for Arabidopsis thaliana. Functional verification for disease stress showed that four GmCNGCs were specifically expressed in the plasmalemma during the stress process. Further, functional enrichment analysis showed that their mode of participation and coordination included inorganic ion concentration regulation inside and outside the membrane via the transmembrane ion channel and participation in stress regulation via signal transduction. The CNGC family genes in G. max involved in disease stress were also identified and physiological stress response and omics analyses were also performed. Our preliminary results revealed the basic laws governing the involvement of CNGCs in disease resistance in G. max, providing important gene resources and a theoretical reference for the breeding of resistant soybean.

The Efficiency of Pest Control Options against Two Major Sweet Corn Ear Pests in China.

Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenée) are the most devastating insect pests at the ear stage of maize, causing significant losses to the sweet corn industry. Pesticide control primarily relies on spraying during the flowering stage, but the effectiveness is inconsistent since larvae are beneath husks within hours to a day, making pesticide treatments simpler to avoid. Insufficient understanding of pest activity patterns impedes precise and efficient pesticide control. H. armigera and O. furnacalis in corn fields were monitored in the last few years in Beijing China, and we observed a higher occurrence of both moths during the R1 stage of sweet corn. Moth captures reached the maximum during this stage, with 555-765 moths per hectare corn field daily. The control efficiency of nine synthetic insecticides and five biopesticides was assessed in the field during this period. Virtako, with mineral oil as the adjuvant, appeared to be the most effective synthetic insecticide, with the efficiencies reaching 88% and 87% on sweet and waxy corn, respectively. Pesticide residue data indicated that the corn is safe after 17 days of its use. The most effective bioinsecticide was Beauveria bassiana combined with mineral oil, with 88% and 80% control efficiency in sweet and waxy corn, respectively. These results suggested that spraying effective insecticides 5 days after corn silking could effectively control corn ear pests H. armigera and O. furnacalis. Our findings provide valuable insights for the development of ear pest management strategies in sweet corn.

A rapid and simplified method for protein silver staining in polyacrylamide gels.

Silver staining is widely used to detect protein in polyacrylamide gels when high sensitivity is required. A simple and rapid protocol for silver staining of proteins following PAGE was developed in the present study. The number of steps was reduced compared to conventional protocol by combining fixing, rinsing, and soaking into a single impregnating step, thus achieving detection of proteins in 20 min. The present method is as sensitive as current protocols with the advantage of saving time and costs.

Cooperative interactions between odorant-binding proteins of Anopheles gambiae.

To understand olfactory discrimination in Anopheles gambiae, we made six purified recombinant OBPs and investigated their ligand-binding properties. All OBPs were expressed in bacteria with additional production of OBP47 in the yeast Kluveromyces lactis. Ligand-binding experiments, performed with a diverse set of organic compounds, revealed marked differences between the OBPs. Using the fluorescent probe N-phenyl-1-naphthylamine, we also measured the binding curves for binary mixtures of OBPs and obtained, in some cases, unexpected behaviour, which could only be explained by the OBPs forming heterodimers with binding characteristics different from those of the component proteins. This shows that OBPs in mosquitoes can form complexes with novel ligand specificities, thus amplifying the repertoire of OBPs and the number of semiochemicals that can be discriminated. Confirmation of the likely role of heterodimers was demonstrated by in situ hybridisation, suggesting that OBP1 and OBP4 are co-expressed in some antennal sensilla of A. gambiae.

Occurrence, Distribution, and Transmission of Alfalfa Viruses in China.

Alfalfa (Medicago sativa L.) is one of the most important quality forages worldwide and is cultivated throughout China. Alfalfa is susceptible to a variety of viral diseases during its growth, which has caused huge amounts of commercial losses. However, the profile of the alfalfa virus in China remains ambiguous and the viruses transmitted by Odontothrips loti (Haliday), dominant insect pests in alfalfa, are also poorly understood. In the present study, virus diversity was investigated in the primary alfalfa-growing areas in China. A total of 18 alfalfa viruses were identified through RNA-sequencing (RNA-seq) and reverse transcription-polymerase chain reaction (RT-PCR). Two new plant viruses, Medicago sativa virus 1 (MsV1) and Medicago sativa luteovirus 1 (MsLV1), were detected for the first time. Another four viruses, including the Alfalfa ringspot-associated virus (ARaV), Alfalfa virus F (AVF), Alfalfa enamovirus 1 (AEV1), and Alfalfa deltaparitivirus (ADPV), were reported in China for the first time as well. Both Alfalfa mosaic virus (AMV) and Medicago sativa alphapartitivirus 2 (MsAPV2) are the dominant pathogens, with an infection incidence of 91.7-100%, and 74.4-97.2%, respectively. Additionally, O. loti with first- and second-instar nymphs were shown to acquire the AMV within 0.25 h of feeding on a virus-infected alfalfa. Transmission by thrips to healthy alfalfa plants was also demonstrated. Additionally, we clarified the dynamic changes in the AMV in pre-adult stages of O. loti, which indicated that the AMV is propagated in the nymph stage of O. loti. These findings provide valuable information for understanding the alfalfa virome, confirm the role thrips O. loti plays in alfalfa virus transmission, and improve our fundamental knowledge and management of diseases in China.

Genome-Wide Selective Signature Analysis Revealed Insecticide Resistance Mechanisms in Cydia pomonella.

The codling moth, Cydia pomonella L. (Lepidoptera, Tortricidae), is a serious invasive pest of pome fruits. Currently, C. pomonella management mainly relies on the application of insecticides, which have driven the development of resistance in the insect. Understanding the genetic mechanisms of insecticide resistance is of great significance for developing new pest resistance management techniques and formulating effective resistance management strategies. Using existing genome resequencing data, we performed selective sweep analysis by comparing two resistant strains and one susceptible strain of the insect pest and identified seven genes, among which, two (glycine receptor and glutamate receptor) were under strong insecticide selection, suggesting their functional importance in insecticide resistance. We also found that eight genes including CYP6B2, CYP307a1, 5-hydroxytryptamine receptor, cuticle protein, and acetylcholinesterase, are potentially involved in cross-resistance to azinphos-methyl and deltamethrin. Moreover, among several P450s identified as positively selected genes, CYP6B2, CYP4C1, and CYP4d2 showed the highest expression level in larva compared to other stages tested, and CYP6B2 also showed the highest expression level in midgut, supporting the roles they may play in insecticide metabolism. Our results provide several potential genes that can be studied further to advance understanding of complexity of insecticide resistance mechanisms in C. pomonella.

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.

Characterization of Antennal Sensilla and Immunolocalization of Odorant-Binding Proteins on Spotted Alfalfa Aphid, Therioaphis trifolii (Monell).

The spotted alfalfa aphid [Therioaphis trifolii (Monell), Homoptera, Drepanosiphidae] is a well-known destructive pest that can significantly reduce alfalfa yields. Herein, the morphology of antennal sensilla of T. trifolii has been examined by using scanning electron microscopy and the ultrastructure of sensilla stellate and placoidea was described by transmission electron microscopy. Stellate sensilla, placoid sensilla, and coeloconic sensilla were found on the 6th segment, and a single sensillum placoidea was located on the 5th segment. Placoid sensilla were also present on the 3rd antennal segment of alate and apterous aphids, and the number was similar between two morphs. Two types of trichoid sensilla and coeloconic sensilla were found on the antennae, respectively. The results of ultrastructure showed that stellate sensilla are innervated by three neurons, while placoid sensilla present three groups of neurons, equipped with 2-3 dendrites in each neuron group. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of sensilla stellate and placoidea, and we observed that the antiserum against OBP6 intensively labeled all placoid sensilla from both primary and secondary rhinaria. OBP7 and OBP8 could also be detected in placoid sensilla, but less strongly than OBP6. In addition, OBP6, OBP7, and OBP8 were densely labeled in stellate sensilla, suggesting OBP6, OBP7, and OBP8 may sense alarm pheromone germacrene A in T. trifolii.