Transcript abundances of <i>A</i>. <i>lucorum</i> OBP genes.

<p>Transcription levels of OBP genes were normalized by GAPDH, and normalized transcript levels to that of male abdomen. The error bar represents standard error and the different small letters above each bar indicate significant differences in transcript abundances (<i>p</i> < 0.05).</p

Alignment of <i>A</i>. <i>lucorum</i> ‘classic’ odorant-binding proteins (OBPs).

<p>Sequences were aligned using the program ClustalW and further edited using BioEdit Sequence Alignment Editor 7.1.3.0. The conserved Cys residues (C1-C6) in the ‘classic’ OBP motif are indicated. Shading represents conservation of sequence identity.</p

Identification and Expression Profiling of Odorant Binding Proteins and Chemosensory Proteins between Two Wingless Morphs and a Winged Morph of the Cotton Aphid <i>Aphis gossypii</i> Glover

<div><p>Insects interact with their environment and respond to the changes in host plant conditions using semiochemicals. Such ecological interactions are facilitated by the olfactory sensilla and the use of olfactory recognition proteins. The cotton aphid <i>Aphis gossypii</i> can change its phenotype in response to ecological conditions. They reproduce mainly as wingless asexual morphs but develop wings to find mates or new plant hosts under the influence of environmental factors such as temperature, plant nutrition and population density. Two groups of small soluble proteins, odorant binding proteins (OBPs) and chemosensory proteins (CSPs) are believed to be involved in the initial biochemical recognition steps in semiochemical perception. However, the exact molecular roles that these proteins play in insect olfaction remain to be discovered. In this study, we compared the transcriptomes of three asexual developmental stages (wingless spring and summer morphs and winged adults) and characterised 9 OBP and 9 CSP genes. The gene structure analysis showed that the number and length of introns in these genes are much higher and this appears to be unique feature of aphid OBP and CSP genes in general. Another unique feature in aphids is a higher abundance of CSP transcripts than OBP transcripts, suggesting an important role of CSPs in aphid physiology and ecology. We showed that some of the transcripts are overexpressed in the antennae in comparison to the bodies and highly expressed in the winged aphids compared to wingless morphs, suggesting a role in host location. We examined the differential expression of these olfactory genes in ten aphid species and compared the expression profile with the RNA-seq analyses of 25 pea aphid transcriptome libraries hosted on AphidBase.</p> </div

Phylogenetic relationship of 192 odorant-binding proteins (OBPs) from 24 Hemipteran species.

<p>Sequences were aligned using MAFFT and the phylogenetic tree constructed using MEGA5 with bootstrap support based on 1000 iterations (only bootstrap values > 60% are shown). Bug sequences are shown in red, AlucOBP sequences are shown in bold italic; Aphid sequences are shown in blue; Planthopper sequences are shown in green.</p

Odorant-binding proteins in <i>A</i>. <i>lucorum</i>.

<p>“—” Genes were obtained by gene cloning and the RPKM values can not be calcuated.</p><p>Odorant-binding proteins in <i>A</i>. <i>lucorum</i>.</p

Molecular Characterization and Expression Profiling of Odorant-Binding Proteins in <i>Apolygus lucorum</i>

<div><p><i>Apolygus lucorum</i> (Meyer-Dür) (Hemiptera: Miridae) is one of the most important agricultural pests, with broad host range and cryptic feeding habits in China. Chemosensory behavior plays an important role in many crucial stages in the life of <i>A</i>. <i>lucorum</i>, such as the detection of sex pheromone cues during mate pursuit and fragrant odorants during flowering host plant localization. Odorant-binding proteins (OBPs) are involved in the initial biochemical recognition steps in semiochemical perception. In the present study, a transcriptomics-based approach was used to identify potential OBPs in <i>A</i>. <i>lucorum</i>. In total, 38 putative OBP genes were identified, corresponding to 26 ‘classic’ OBPs and 12 ‘Plus-C’ OBPs. Phylogenetic analysis revealed that <i>A</i>. <i>lucorum</i> OBP proteins are more closely related to the OBP proteins of other mirid bugs as the same family OBP clustering together. Quantitative real-time PCR analysis for the first reported 23 AlucOBPs revealed that the expression level of 11 AlucOBP genes were significantly higher in antennae of both sexes than in other tissues. Three of them were male antennae-biased and six were female antennae-biased, suggesting their putative roles in the detection of female sex pheromones and host plant volatiles. In addition, three, four, two and one AlucOBPs had the highest degree of enrichment in the stylet, head, leg, and in abdomen tissues, respectively. Two other OBPs were ubiquitously expressed in the main tissues, including antennae, stylets, heads, legs and wings. Most orthologs had similar expression patterns, strongly indicating that these genes have the same function in olfaction and gustation.</p></div

Number of annotated OBP and CSP genes in insect genomes.

<p>Agos: <i>Aphis </i><i>gossypii</i>. <i>Apis: Acyrthosiphon pisum</i>. Bmor: <i>Bombyx </i><i>mori</i>. Amel: <i>Apis </i><i>mellifera</i>. Dmel: <i>Drosophila </i><i>melanogaster</i>.</p

Phylogenetic tree of 62 OBPs from 12 aphid species.

<p>Numbers on branches show values of 1000 times replication bootstrap analysis and the bootstrap values are listed at each node. Accession numbers of the 62 aphid OBPs are as follow: Agos, <i>Aphis </i><i>gossypii</i>. The accession numbers of AgosOBP2-10 are listed in Table 1. Psal, <i>Pterocomma </i><i>salicis</i> (PsalOBP1: CAR85660; PsalOBP2: CAR85661; PsalOBP4: CAR85662; PsalOBP9: CAR85663; PsalOBP10: CAX63261); Afab, <i>Aphis </i><i>fabae</i> (AfabOBP2: CAR85656; AfabOBP8: CAR85657); Acra, <i>Aphis </i><i>craccivora</i> (AcraOBP2; CAR85658); Tsal, <i>Tuberolachnus </i><i>salignus</i> (TsalOBP1: CAR85659); Mvic, <i>Megoura </i><i>viciae</i> (MvicOBP1: CAR85650; MvicOBP2: CAR85651; MvicOBP5: CAR85652; MvicOBP8: CAR85653; MvicOBP10: CAX63260); Mdir, <i>Metopolophium </i><i>dirhodum</i> (MdirOBP1: CAR85638; MdirOBP2: CAR85639; MdirOBP3: CAX63256; MdirOBP4: CAR85640; MdirOBP5: CAR85641; MdirOBP6: CAR85642; MdirOBP8: CAR85643); Mper, <i>Myzus </i><i>persicae</i> (MperOBP3: CAR85644; MperOBP4: CAR85645; MperOBP6: CAR85646; MperOBP7: CAR85647; MperOBP8: CAR85648; MperOBP10: CAR85649); Nrib, <i>Nasonovia </i><i>ribis-nigri</i> (NribOBP2: CAR85654; NribOBP3: CAX63257; NribOBP5: CAX63258; NribOBP7: CAX63259; NribOBP8: CAR85655). Save, <i>Sitobion </i><i>avenae</i> (SaveOBP2: CAX63247; SaveOBP3: CAX63248; SaveOBP4: CAX63249; SaveOBP5: CAX63250; SaveOBP6: CAX63251; SaveOBP7: ACW03675; SaveOBP9: GQ847860; SaveOBP10: CAX63252); Rpad, <i>Rhopalosiphum </i><i>padi</i> (RpadOBP2: CAX63253; RpadOBP5: CAX63254; RpadOBP10: CAX63255). Apis, <i>Acyrthosiphon </i><i>pisum</i> (ApisOBP1-AipsOBP10: CAR85628-CAR85637).</p

Tissue-specific expression profiles of <i>A</i>.

<div><p><b><i>gossypii</i> OBPs and CSPs as measured by qRT-PCR</b>. </p> <p>The fold changes are relative to the transcript levels in the body. Standard errors represented by the error bars, and the letter above each bar indicates the statistical differences; the bars with different letters (a, b, c) indicate significant differences (<i>p</i><0.05) and with same letters indicate no differences between mean expression levels.</p></div

Introns in OBP and CSP genes.

<p>(A) intron number, (B) intron length. Agos: <i>Aphis </i><i>gossypii</i>. <i>Apis: Acyrthosiphon pisum</i>. Bmor: <i>Bombyx </i><i>mori</i>. Amel: <i>Apis </i><i>mellifera</i>. Dmel: <i>Drosophila </i><i>melanogaster</i>.</p