Chromosome-level genome of black cutworm provides novel insights into polyphagy and seasonal migration in insects.

BACKGROUND: The black cutworm, Agrotis ipsilon, is a serious global underground pest. Its distinct phenotypic traits, especially its polyphagy and ability to migrate long distances, contribute to its widening distribution and increasing difficulty of control. However, knowledge about these traits is still limited. RESULTS: We generated a high-quality chromosome-level assembly of A. ipsilon using PacBio and Hi-C technology with a contig N50 length of ~ 6.7 Mb. Comparative genomic and transcriptomic analyses showed that detoxification-associated gene families were highly expanded and induced after insects fed on specific host plants. Knockout of genes that encoded two induced ABC transporters using CRISPR/Cas9 significantly reduced larval growth rate, consistent with their contribution to host adaptation. A comparative transcriptomic analysis between tethered-flight moths and migrating moths showed expression changes in the circadian rhythm gene AiCry2 involved in sensing photoperiod variations and may receipt magnetic fields accompanied by MagR and in genes that regulate the juvenile hormone pathway and energy metabolism, all involved in migration processes. CONCLUSIONS: This study provides valuable genomic resources for elucidating the mechanisms involved in moth migration and developing innovative control strategies.

EndHiC: assemble large contigs into chromosome-level scaffolds using the Hi-C links from contig ends.

BACKGROUND: The application of PacBio HiFi and ultra-long ONT reads have enabled huge progress in the contig-level assembly, but it is still challenging to assemble large contigs into chromosomes with available Hi-C scaffolding tools, which count Hi-C links between contigs using the whole or a large part of contig regions. As the Hi-C links of two adjacent contigs concentrate only at the neighbor ends of the contigs, larger contig size will reduce the power to differentiate adjacent (signal) and non-adjacent (noise) contig linkages, leading to a higher rate of mis-assembly. RESULTS: We design and develop a novel Hi-C based scaffolding tool EndHiC, which is suitable to assemble large contigs into chromosomal-level scaffolds. The core idea behind EndHiC, which distinguishes it from other Hi-C scaffolding tools, is using Hi-C links only from the most effective regions of contig ends. By this way, the signal neighbor contig linkages and noise non-neighbor contig linkages are separated more clearly. Benefiting from the increased signal to noise ratio, the reciprocal best requirement, as well as the robustness evaluation, EndHiC achieves higher accuracy for scaffolding large contigs compared to existing tools. EndHiC has been successfully applied in the Hi-C scaffolding of simulated data from human, rice and Arabidopsis, and real data from human, great burdock, water spinach, chicory, endive, yacon, and Ipomoea cairica, suggesting that EndHiC can be applied to a broad range of plant and animal genomes. CONCLUSIONS: EndHiC is a novel Hi-C scaffolding tool, which is suitable for scaffolding of contig assemblies with contig N50 size near or over 10 Mb and N90 size near or over 1 Mb. EndHiC is efficient both in time and memory, and it is interface-friendly to the users. As more genome projects have been launched and the contig continuity constantly improved, we believe EndHiC has the potential to make a great contribution to the genomics field and liberate the scientists from labor-intensive manual curation works.

Haplotype-resolved chromosome-level genome of hexaploid Jerusalem artichoke provides insights into its origin, evolution, and inulin metabolism.

Jerusalem artichoke (Helianthus tuberosus) is a global multifunctional crop. It has wide applications in the food, health, feed, and biofuel industries and in ecological protection; it also serves as a germplasm pool for breeding of the global oil crop common sunflower (Helianthus annuus). However, biological studies of Jerusalem artichoke have been hindered by a lack of genome sequences, and its high polyploidy and large genome size have posed challenges to genome assembly. Here, we report a 21-Gb chromosome-level assembly of the hexaploid Jerusalem artichoke genome, which comprises 17 homologous groups, each with 6 pseudochromosomes. We found multiple large-scale chromosome rearrangements between Jerusalem artichoke and common sunflower, and our results show that the hexaploid genome of Jerusalem artichoke was formed by a hybridization event between a tetraploid and a diploid Helianthus species, followed by chromosome doubling of the hybrid, which occurred approximately 2 million years ago. Moreover, we identified more copies of actively expressed genes involved in inulin metabolism and showed that these genes may still be undergoing loss of function or sub- or neofunctionalization. These genomic resources will promote further biological studies, breeding improvement, and industrial utilization of Helianthus crops.

The genomes of Dahlia pinnata, Cosmos bipinnatus, and Bidens alba in tribe Coreopsideae provide insights into polyploid evolution and inulin biosynthesis.

BACKGROUND: The Coreopsideae tribe, a subset of the Asteraceae family, encompasses economically vital genera like Dahlia, Cosmos, and Bidens, which are widely employed in medicine, horticulture, ecology, and food applications. Nevertheless, the lack of reference genomes hinders evolutionary and biological investigations in this tribe. RESULTS: Here, we present 3 haplotype-resolved chromosome-level reference genomes of the tribe Coreopsideae, including 2 popular flowering plants (Dahlia pinnata and Cosmos bipinnatus) and 1 invasive weed plant (Bidens alba), with assembled genome sizes 3.93 G, 1.02 G, and 1.87 G, respectively. We found that Gypsy transposable elements contribute mostly to the larger genome size of D. pinnata, and multiple chromosome rearrangements have occurred in tribe Coreopsideae. Besides the shared whole-genome duplication (WGD-2) in the Heliantheae alliance, our analyses showed that D. pinnata and B. alba each underwent an independent recent WGD-3 event: in D. pinnata, it is more likely to be a self-WGD, while in B. alba, it is from the hybridization of 2 ancestor species. Further, we identified key genes in the inulin metabolic pathway and found that the pseudogenization of 1-FEH1 and 1-FEH2 genes in D. pinnata and the deletion of 3 key residues of 1-FFT proteins in C. bipinnatus and B. alba may probably explain why D. pinnata produces much more inulin than the other 2 plants. CONCLUSIONS: Collectively, the genomic resources for the Coreopsideae tribe will promote phylogenomics in Asteraceae plants, facilitate ornamental molecular breeding improvements and inulin production, and help prevent invasive weeds.

Identification and functional analysis of odorant-binding proteins provide new control strategies for Apolygus lucorum.

The green bug Apolygus lucorum is a notorious pest that feeds on multiple crops, including fruit trees, vegetables, and cotton. The odorant-binding proteins (OBPs) are considered to perform crucial roles in regulating A. lucorum behaviors such as mating and feeding. In this study, we first identified OBPs in the A. lucorum genome. Then, we calculated the expression levels of these OBP genes in different tissues and stages. Thereafter, we conducted ligand-binding assay to test the interactions between nine selected AlucOBPs and multiple chemical compounds. The result showed that there were 31 OBP genes encoding 39 transcripts in the A. lucorum genome, and several OBP clusters were found. Comprehensive expression profiling revealed the tissue-specific expression of some OBP genes. The results of fluorescence competitive binding assays showed that these nine AlucOBPs could specifically bind to plant volatiles, nonvolatile compounds, and synthetic analogs thereof. Additionally, AlucOBP19 was suggested to function in gustatory sensing to avoid deleterious plant secondary metabolites, as AlucOBP19 showed high expression in the mouthparts and legs and could interact with quercetin. Our findings highlight the potential biotechnological application of plant volatiles and their synthetic analogs as ecological attractants and provide new gene targets for control of A. lucorum.

Chromosome-level genomes of two armyworms, Mythimna separata and Mythimna loreyi, provide insights into the biosynthesis and reception of sex pheromones.

Mythimna separata and Mythimna loreyi are global pests of gramineous cereals, heavily controlled with synthetic insecticides. Here, we generated two high-quality chromosome-level genome assemblies for M. separata (688 Mb) and M. loreyi (683 Mb). Our analysis identified Z and W chromosomes, with few genes and abundant transposable elements (TEs) found on the W chromosome. We also observed a recent explosion of long interspersed nuclear elements (LINEs), which contributed to the larger genomes of Mythimna. The two armyworms diverged ~10.5 MYA, with only three chromosomes have intrachromosomal rearrangements. Additionally, we observed a tandem repeat expansion of α-amylase genes in Mythimna, which may promote the digestion of carbohydrates and exacerbate their damage to crops. Furthermore, we inferred the sex pheromone biosynthesis pathway for M. separata, M. loreyi and Spodoptera frugiperda. We discovered that M. loreyi and S. frugiperda synthesized the same major constituents of sex pheromones through different pathways. Specifically, the double bonds in the dominant sex pheromone components of S. frugiperda were generated by Δ9- and Δ11-desaturase, while they were generated by Δ11-desaturase and chain-shortening reactions in M. loreyi. We also identified pheromone receptor (PR) genes and inferred their corresponding components. These findings provide a better understanding of sex pheromone communication and promote the development of a new pest control strategy involving pheromone traps, which are more effective and environmentally friendly than current strategies.

Adaptive evolution to the natural and anthropogenic environment in a global invasive crop pest, the cotton bollworm.

The cotton bollworm, Helicoverpa armigera, is set to become the most economically devastating crop pest in the world, threatening food security and biosafety as its range expands across the globe. Key to understanding the eco-evolutionary dynamics of H. armigera, and thus its management, is an understanding of population connectivity and the adaptations that allow the pest to establish in unique environments. We assembled a chromosome-scale reference genome and re-sequenced 503 individuals spanning the species range to delineate global patterns of connectivity, uncovering a previously cryptic population structure. Using a genome-wide association study (GWAS) and cell line expression of major effect loci, we show that adaptive changes in a temperature- and light-sensitive developmental pathway enable facultative diapause and that adaptation of trehalose synthesis and transport underlies cold tolerance in extreme environments. Incorporating extensive pesticide resistance monitoring, we also characterize a suite of novel pesticide and Bt resistance alleles under selection in East China. These findings offer avenues for more effective management strategies and provide insight into how insects adapt to variable climatic conditions and newly colonized environments.

Chromosome-level genome of the globe skimmer dragonfly (Pantala flavescens).

BACKGROUND: The globe skimmer dragonfly (Pantala flavescens) is a notable Odonata insect distributed in nature fields and farmlands worldwide, and it is commonly recognized as a natural enemy because it preys on agricultural pests and health pests. As one of the sister groups of winged insects, odonatan species are key to understanding the evolution of insect wings. FINDINGS: We present a high-quality reference genome of P. flavescens, which is the first chromosome-level genome in the Palaeoptera (Odonata and Ephemeroptera). The assembled genome size was 662 Mb, with a contig N50 of 16.2 Mb. Via Hi-C scaffolding, 648 Mb (97.9%) of contig sequences were clustered, ordered, and assembled into 12 large scaffolds, each corresponding to a natural chromosome. The X chromosome was identified by sequence coverage depth. The repetitive sequences and gene density of the X chromosome are similar to those of autosomal sequences, but the X chromosome shows a much lower degree of heterozygosity. Our analysis shows that the effective population size experienced 3 declining events, which may have been caused by climate change and environmental pollution. CONCLUSIONS: The genome of P. flavescens provides more information on the biology and evolution of insects and will help for the use of this species in pest control.

The genomes of chicory, endive, great burdock and yacon provide insights into Asteraceae palaeo-polyploidization history and plant inulin production.

Inulin is an important reserve polysaccharide in Asteraceae plants, and is also widely used as a sweetener, a source of dietary fibre and prebiotic. Nevertheless, a lack of genomic resources for inulin-producing plants has hindered extensive studies on inulin metabolism and regulation. Here, we present chromosome-level reference genomes for four inulin-producing plants: chicory (Cichorium intybus), endive (Cichorium endivia), great burdock (Arctium lappa) and yacon (Smallanthus sonchifolius), with assembled genome sizes of 1.28, 0.89, 1.73 and 2.72 Gb, respectively. We found that the chicory, endive and great burdock genomes were shaped by whole genome triplication (WGT-1), and the yacon genome was shaped by WGT-1 and two subsequent whole genome duplications (WGD-2 and WGD-3). A yacon unique whole genome duplication (WGD-3) occurred 5.6-5.8 million years ago. Our results also showed the genome size difference between chicory and endive is largely due to LTR retrotransposons, and rejected a previous hypothesis that chicory is an ancestor of endive. Furthermore, we identified fructan-active-enzyme and transcription-factor genes, and found there is one copy in chicory, endive and great burdock but two copies in yacon for most of these genes, except for the 1-FEH II gene which is significantly expanded in chicory. Interestingly, inulin synthesis genes 1-SST and 1-FFT are located close to each other, as are the degradation genes 1-FEH I and 1-FEH II. Finally, we predicted protein structures for 1-FFT genes to explore the mechanism determining inulin chain length.

A chromosome-level reference genome of a Convolvulaceae species Ipomoea cairica.

Ipomoea cairica is a perennial creeper that has been widely introduced as a garden ornamental across tropical, subtropical, and temperate regions. Because it grows extremely fast and spreads easily, it has been listed as an invasive species in many countries. Here, we constructed the chromosome-level reference genome of Ipomoea cairica by Pacific Biosciences HiFi and Hi-C sequencing, with the assembly size of 733.0 Mb, the contig N50 of 43.8 Mb, the scaffold N50 of 45.7 Mb, and the Benchmarking Universal Single-Copy Orthologs complete rate of 98.0%. Hi-C scaffolding assigned 97.9% of the contigs to 15 pseudo-chromosomes. Telomeric repeat analysis reveals that 7 of the 15 pseudo-chromosomes are gapless and telomere to telomere. The transposable element content of Ipomoea cairica is 73.4%, obviously higher than that of other Ipomoea species. A total of 38,115 protein-coding genes were predicted, with the Benchmarking Universal Single-Copy Orthologs complete rate of 98.5%, comparable to that of the genome assembly, and 92.6% of genes were functional annotated. In addition, we identified 3,039 tRNA genes and 2,403 rRNA genes in the assembled genome. Phylogenetic analysis showed that Ipomoea cairica formed a clade with Ipomoea aquatica, and they diverged from each other 8.1 million years ago. Through comparative genome analysis, we reconfirmed that a whole genome triplication event occurred specific to Convolvulaceae family and in the ancestor of the genus Ipomoea and Cuscuta. This high-quality reference genome of Ipomoea cairica will greatly facilitate the studies on the molecular mechanisms of its rapid growth and invasiveness.

A microbial gene catalog of anaerobic digestion from full-scale biogas plants.

BACKGROUND: Biogas production with anaerobic digestion (AD) is one of the most promising solutions for both renewable energy production and resolving the environmental problem caused by the worldwide increase in organic waste. However, the complex structure of the microbiome in AD is poorly understood. FINDINGS: In this study, we constructed a microbial gene catalog of AD (22,840,185 genes) based on 1,817 Gb metagenomic data derived from digestate samples of 56 full-scale biogas plants fed with diverse feedstocks. Among the gene catalog, 73.63% and 2.32% of genes were taxonomically annotated to Bacteria and Archaea, respectively, and 57.07% of genes were functionally annotated with KEGG orthologous groups. Our results confirmed the existence of core microbiome in AD and showed that the type of feedstock (cattle, chicken, and pig manure) has a great influence on carbohydrate hydrolysis and methanogenesis. In addition, 2,426 metagenome-assembled genomes were recovered from all digestate samples, and all genomes were estimated to be ≥80% complete with ≤10% contamination. CONCLUSIONS: This study deepens our understanding of the microbial composition and function in the AD process and also provides a huge number of reference genome and gene resources for analysis of anaerobic microbiota.

Wheat Rhizosphere Metagenome Reveals Newfound Potential Soil Zn-Mobilizing Bacteria Contributing to Cultivars' Variation in Grain Zn Concentration.

An effective solution to global human zinc (Zn) deficiency is Zn biofortification of staple food crops, which has been hindered by the low available Zn in calcareous soils worldwide. Many culturable soil microbes have been reported to increase Zn availability in the laboratory, while the status of these microbes in fields and whether there are unculturable Zn-mobilizing microbes remain unexplored. Here, we use the culture-independent metagenomic sequencing to investigate the rhizosphere microbiome of three high-Zn (HZn) and three low-Zn (LZn) wheat cultivars in a field experiment with calcareous soils. The average grain Zn concentration of HZn was higher than the Zn biofortification target 40 mg kg-1, while that of LZn was lower than 40 mg kg-1. Metagenomic sequencing and analysis showed large microbiome difference between wheat rhizosphere and bulk soil but small difference between HZn and LZn. Most of the rhizosphere-enriched microbes in HZn and LZn were in common, including many of the previously reported soil Zn-mobilizing microbes. Notably, 30 of the 32 rhizosphere-enriched species exhibiting different abundances between HZn and LZn possess the functional genes involved in soil Zn mobilization, especially the synthesis and exudation of organic acids and siderophores. Most of the abundant potential Zn-mobilizing species were positively correlated with grain Zn concentration and formed a module with strong interspecies relations in the co-occurrence network of abundant rhizosphere-enriched microbes. The potential Zn-mobilizing species, especially Massilia and Pseudomonas, may contribute to the cultivars' variation in grain Zn concentration, and they deserve further investigation in future studies on Zn biofortification.

Variation of Metagenome From Feedstock to Digestate in Full-Scale Biogas Plants.

Anaerobic digestion (AD) has been widely used to resolve the problem of organic wastes worldwide. Previous studies showed that the types of feedstock have a great influence on the AD microbiome, and a huge number of AD populations are migrated from upstream feedstocks. However, the changes of microbial compositions from feedstock to AD digestate are still less understood. We collected feedstock samples from 56 full-scale biogas plants, generated 1,716 Gb feedstock metagenomic data in total, and constructed the first comprehensive microbial gene catalog of feedstock containing 25.2 million genes. Our result indicated that the predominant phyla in feedstock are Firmicutes, Bacteroidetes, and Proteobacteria, which is similar to that in AD digestate, and the microbial diversity of feedstock samples is higher than that of AD digestate samples. In addition, the relative abundance of most genes involved in methanogenesis increase from feedstock to AD digestate. Besides, the amount of antibiotic resistance genes (ARGs) and pathogenic bacteria in AD are effectively reduced compared to feedstocks. This study provides a comprehensive microbial gene catalog of feedstock, and deepens the understanding of variation of microbial communities from feedstock to AD digestate of full-scale AD. The results also suggest the potential of AD to reduce the level of ARGs and pathogens in animal manure.

Apolygus lucorum genome provides insights into omnivorousness and mesophyll feeding.

Apolygus lucorum (Miridae) is an omnivorous pest that occurs worldwide and is notorious for the serious damage it causes to various crops and substantial economic losses. Although some studies have examined the biological characteristics of the mirid bug, no reference genome is available in Miridae, limiting in-depth studies of this pest. Here, we present a chromosome-scale reference genome of A. lucorum, the first sequenced Miridae species. The assembled genome size was 1.02 Gb with a contig N50 of 785 kb. With Hi-C scaffolding, 1,016 Mb contig sequences were clustered, ordered and assembled into 17 large scaffolds with scaffold N50 length 68 Mb, each corresponding to a natural chromosome. Numerous transposable elements occur in this genome and contribute to the large genome size. Expansions of genes associated with omnivorousness and mesophyll feeding such as those related to digestion, chemosensory perception, and detoxification were observed in A. lucorum, suggesting that gene expansion contributed to its strong environmental adaptability and severe harm to crops. We clarified that a salivary enzyme polygalacturonase is unique in mirid bugs and has significantly expanded in A. lucorum, which may contribute to leaf damage from this pest. The reference genome of A. lucorum not only facilitates biological studies of Hemiptera as well as an understanding of the damage mechanism of mesophyll feeding, but also provides a basis on which to develop efficient control technologies for mirid bugs.

Giant African snail genomes provide insights into molluscan whole-genome duplication and aquatic-terrestrial transition.

Whole-genome duplication (WGD), contributing to evolutionary diversity and environmental adaptability, has been observed across a wide variety of eukaryotic groups, but not in molluscs. Molluscs are the second largest animal phylum in terms of species numbers, and among the organisms that have successfully adapted to the nonmarine realm through aquatic-terrestrial (A-T) transition. We assembled a chromosome-level reference genome for Achatina immaculata, a globally invasive species, and compared the genomes of two giant African snails (A. immaculata and Achatina fulica) to other available mollusc genomes. Macrosynteny, colinearity blocks, Ks peak and Hox gene clusters collectively suggested a WGD event in the two snails. The estimated WGD timing (~70 million years ago) was close to the speciation age of the Sigmurethra-Orthurethra (within Stylommatophora) lineage and the Cretaceous-Tertiary (K-T) mass extinction, indicating that the WGD may have been a common event shared by all Sigmurethra-Orthurethra species and conferred ecological adaptability allowing survival after the K-T extinction event. Furthermore, the adaptive mechanism of WGD in terrestrial ecosystems was confirmed by the presence of gene families related to the respiration, aestivation and immune defence. Several mucus-related gene families expanded early in the Stylommatophora lineage, and the haemocyanin and phosphoenolpyruvate carboxykinase families doubled during WGD, and zinc metalloproteinase genes were highly tandemly duplicated after WGD. This evidence suggests that although WGD may not have been the direct driver of the A-T transition, it played an important part in the terrestrial adaptation of giant African snails.

The Rhizosphere Microbiome of Mikania micrantha Provides Insight Into Adaptation and Invasion.

Mikania micrantha is a noxious invasive plant causing enormous economic losses and ecological damage. Soil microbiome plays an important role in the invasion process of M. micrantha, while little is known about its rhizosphere microbiome composition and function. In this study, we identified the distinct rhizosphere microbial communities of M. micrantha, by comparing them with those of two coexisting native plants (Polygonum chinense and Paederia scandens) and the bulk soils, using metagenomics data from field sampling and pot experiment. As a result, the enrichment of phosphorus-solubilizing bacteria Pseudomonas and Enterobacter was consistent with the increased soil available phosphorus in M. micrantha rhizosphere. Furthermore, the pathogens of Fusarium oxysporum and Ralstonia solanacearum and pathogenic genes of type III secretion system (T3SS) were observed to be less abundant in M. micrantha rhizosphere, which might be attributed to the enrichment of biocontrol bacteria Catenulispora, Pseudomonas, and Candidatus Entotheonella and polyketide synthase (PKS) genes involved in synthesizing antibiotics and polyketides to inhibit pathogens. These findings collectively suggested that the enrichment of microbes involved in nutrient acquisition and pathogen suppression in the rhizosphere of M. micrantha largely enhances its adaptation and invasion to various environments.

Mikania micrantha genome provides insights into the molecular mechanism of rapid growth.

Mikania micrantha is one of the top 100 worst invasive species that can cause serious damage to natural ecosystems and substantial economic losses. Here, we present its 1.79 Gb chromosome-scale reference genome. Half of the genome is composed of long terminal repeat retrotransposons, 80% of which have been derived from a significant expansion in the past one million years. We identify a whole genome duplication event and recent segmental duplications, which may be responsible for its rapid environmental adaptation. Additionally, we show that M. micrantha achieves higher photosynthetic capacity by CO2 absorption at night to supplement the carbon fixation during the day, as well as enhanced stem photosynthesis efficiency. Furthermore, the metabolites of M. micrantha can increase the availability of nitrogen by enriching the microbes that participate in nitrogen cycling pathways. These findings collectively provide insights into the rapid growth and invasive adaptation.

Key Amino Residues Determining Binding Activities of the Odorant Binding Protein AlucOBP22 to Two Host Plant Terpenoids of Apolygus lucorum.

Odorant binding proteins (OBPs) are considered to be highly expressed at antennae sensillum lymph and play crucial roles in detection of insect host plant volatiles. The polyphagous mirid bug Apolygus lucorum is one of a series of insect pests on many important agricultural crops that heavily rely on sophisticated olfaction to locate host plants. Previously, putative OBP genes and their tissue-related expression patterns in this pest species have been clarified. In this study, we characterized the ligand spectrum and the molecular binding mechanism of the antennae-biased AlucOBP22 to host plant volatiles of A. lucorum. Frist, the recombinant AlucOBP22 protein was constructed and purified, and its binding affinities to selected host plant volatiles were assessed. Two terpenoids, ß-ionone and ß-caryophyllene, could highly bind to AlucOBP22. Next, three-dimensional model prediction indicated that AlucOBP22 employed six α-helices to form a typical pocket for ligand accommodation. Molecular docking analysis suggested that both ß-ionone and ß-caryophyllene were located at the AlucOBP22 pocket with some hydrophobic amino acid residues close to the two chemicals, suggesting that hydrophobic interactions might be crucial for ligand-specific binding. Finally, site-directed mutagenesis combined with fluorescence binding assays revealed that mutants of five hydrophobic residues Leu5, Ile40, Met41, Val44, and Met45 displayed significantly decreased or completely abolished binding affinities to the two ligands. Our findings showed the specific binding characteristic of AlucOBP22 and suggested that hydrophobic residues and their hydrophobic interactions were involved in AlucOBP22 binding to terpenoids, which provided new insights into the molecular interaction mechanisms of hemipteran insect OBPs to host plant odors.

Odorant-binding and chemosensory proteins identified in the antennal transcriptome of Adelphocoris suturalis Jakovlev.

Adelphocoris suturalis Jakovlev (Hemiptera: Miridae) is an insect pest that causes severe agricultural damage to cotton and many other important crops. In insects, olfaction is very important throughout their lifetime. There are two groups of small soluble proteins, named odorant binding proteins (OBPs) and chemosensory proteins (CSPs), which are suggested to participate in the initial biochemical recognition steps of insect olfactory signal transduction. In this study, a total of 16 OBPs (12 classical OBPs and 4 plus-C OBPs) and 8 CSPs, were identified in the antennal transcriptome of A. suturalis. The sex- and tissue-specific profiles of these binding protein genes showed that 13 of the 16 OBP transcripts were highly expressed in the antennae of both sexes, and 4 OBPs (AsutOBP1, 4, 5 and 9) were expressed higher in the male antennae compared to the female antennae. Three CSPs (AsutCSP1, 4 and 5) were expressed specifically in the antennae of both sexes, and AsutCSP1 was expressed higher in the male antennae than in the female antennae. Our findings identify several novel OBP and CSP genes for further investigation of the olfactory system of A. suturalis at the molecular level.

Identification and expression analysis of an olfactory receptor gene family in green plant bug Apolygus lucorum (Meyer-Dür).

Olfactory receptors are believed to play a central role in insects host-seeking, mating, and ovipositing. On the basis of male and female antennal transcriptome of adult Apolygus lucorum, a total of 110 candidate A. lucorum odorant receptors (AlucOR) were identified in this study including five previously annotated AlucORs. All the sequences were validated by cloning and sequencing. Tissue expression profiles analysis by RT-PCR indicated most AlucORs were antennal highly expressed genes. The qPCR measurements further revealed 40 AlucORs were significantly higher in the antennae. One AlucOR was primarily expressed in the female antennae, while nine AlucORs exhibited male-biased expression patterns. Additionally, both the RPKM value and RT-qPCR analysis showed AlucOR83 and AlucOR21 were much higher abundant in male antennae than in female antennae, suggesting their different roles in chemoreception of gender. Phylogenetic analysis of ORs from several Hemipteran species demonstrated that most AlucORs had orthologous genes, and five AlucOR-specific clades were defined. In addition, a sub-clade of potential male-based sex pheromone receptors were also identified in the phylogenetic tree of AlucORs. Our results will facilitate the functional studies of AlucORs, and thereby provide a foundation for novel pest management approaches based on these genes.