Aphids are infected with a wide variety of endosymbionts that can confer ecologically relevant traits. However, the bacterial communities of most aphid species are still poorly characterized. This study investigated the bacterial diversity of the cotton aphid Aphis gossypii associated with Bt cotton in northern China by targeting the V4 region of the 16S rDNA using the Illumina MiSeq platform. Our sequencing data revealed that bacterial communities of A. gossypii were generally dominated by the primary symbiont Buchnera, together with the facultative symbionts Arsenophonus and Hamiltonella. To our knowledge, this is the first report documenting the facultative symbiont Hamiltonella in A. gossypii. Moreover, the bacterial community structure was similar within aphids from the same province, but distinct among those from different provinces. The taxonomic diversity of the bacterial community is greater in Hebei Province compared with in samples from Henan and Shandong Provinces. The selection pressure exerted by the different geographical locations could explain the differences found among the various provinces. These findings broaden our understanding of the interactions among aphids, endosymbionts and their environments, and provide clues to develop potential biocontrol techniques against this cotton aphid.

BackgroundThe cotton-melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a polyphagous species with a worldwide distribution and a variety of biotypes. North China is a traditional agricultural area with abundant winter and summer hosts of A. gossypii. While the life cycles of A. gossypii on different plants have been well studied, those of the biotypes of North China are still unclear.ResultsHost transfer experiments showed that A. gossypii from North China has two host-specialized biotypes: cotton and cucumber. Based on complete mitochondrial sequences, we identified a molecular marker with five single-nucleotide polymorphisms to distinguish the biotypes. Using this marker, a large-scale study of biotypes on primary winter and summer hosts was conducted. All A. gossypii collected from three primary hosts—hibiscus, pomegranate, and Chinese prickly ash—were cotton biotypes, with more cotton-melon aphids found on hibiscus than the other two species. In May, alate cotton and cucumber biotypes coexisted on cotton and cucumber seedlings, but each preferred its natal host. Both biotypes existed on zucchini, although the cucumber biotype was more numerous. Aphids on muskmelon were all cucumber biotypes, whereas most aphids on kidney bean were cotton biotypes. Aphids on seedlings of potato and cowpea belong to other species. In August, aphids on cotton and cucumber were the respective biotypes, with zucchini still hosting both biotypes as before. Thus, the biotypes had different fitnesses on different host plants.ConclusionsTwo host-specialized biotypes (cotton and cucumber) are present in North China. Hibiscus, pomegranate, and Chinese prickly ash can serve as winter hosts for the cotton biotype but not the cucumber biotype in North China. The fitnesses of the two host-specialized biotypes differ on various summer hosts. When alate aphids migrate to summer hosts, they cannot accurately land on the corresponding plant.

No abstract

For the sucking insect, Apolygus lucorum, taste is essential for finding host plants and oviposition sites. In A. lucorum, taste relies largely on the sensory system located within its proboscis. In this study, we constructed a cDNA library from A. lucorum proboscises and conducted preliminary analysis of 1554 ESTs. From this collection, we identified three putative odorant-binding proteins (AlucOBP3, AlucOBP4, AlucOBP6) and one chemosensory protein (AlucCSP1). Quantitative real-time polymerase chain reaction (qPCR) was used to study the expression pattern of these four genes. All four were expressed mainly in antennae, proboscises and legs, suggestive of roles in olfaction and gustation. We expressed and purified recombinant versions of AlucOBP3, AlucOBP4, AlucOBP6, and AlucCSP1 in a prokaryotic expression system. The ligand-binding specificities of the four proteins then were investigated in competition assays using 4,4'-dianilino-1,1'-binaphthyl-5, 5'-sulfonic acid (bis-ANS) as a probe. Of the 58 small organic compounds and five cotton secondary metabolites tested, plant volatiles cannot effectively displace bis-ANS from any of the four proteins. In contrast, most of the cotton secondary metabolites have high affinities for the three OBPs and AlucCSP1, indicating that these binding proteins more likely play a role in gustation than in olfaction.

Background Chrysopa pallens (Rambur) are the most important natural enemies and predators of various agricultural pests. Understanding the sophisticated olfactory system in insect antennae is crucial for studying the physiological bases of olfaction and also could lead to effective applications of C. pallens in integrated pest management. However no transcriptome information is available for Neuroptera, and sequence data for C. pallens are scarce, so obtaining more sequence data is a priority for researchers on this species.ResultsTo facilitate identifying sets of genes involved in olfaction, a normalized transcriptome of C. pallens was sequenced. A total of 104,603 contigs were obtained and assembled into 10,662 clusters and 39,734 singletons; 20,524 were annotated based on BLASTX analyses. A large number of candidate chemosensory genes were identified, including 14 odorant-binding proteins (OBPs), 22 chemosensory proteins (CSPs), 16 ionotropic receptors, 14 odorant receptors, and genes potentially involved in olfactory modulation. To better understand the OBPs, CSPs and cytochrome P450s, phylogenetic trees were constructed. In addition, 10 digital gene expression libraries of different tissues were constructed and gene expression profiles were compared among different tissues in males and females.ConclusionsOur results provide a basis for exploring the mechanisms of chemoreception in C. pallens, as well as other insects. The evolutionary analyses in our study provide new insights into the differentiation and evolution of insect OBPs and CSPs. Our study provided large-scale sequence information for further studies in C. pallens.

Differences in sex pheromone component can lead to reproductive isolation. The sibling noctuid species, Helicoverpa armigera and Helicoverpa assulta, share the same two sex pheromone components, Z9-16:Ald and Z11-16:Ald, but in opposite ratios, providing an typical example of such reproductive isolation. To investigate how the ratios of the pheromone components are differently regulated in the two species, we sequenced cDNA libraries from the pheromone glands of H. armigera and H. assulta. After assembly and annotation, we identified 108 and 93 transcripts putatively involved in pheromone biosynthesis, transport, and degradation in H. armigera and H. assulta, respectively. Semi-quantitative RT-PCR, qRT-PCR, phylogenetic, and mRNA abundance analyses suggested that some of these transcripts involved in the sex pheromone biosynthesis pathways perform. Based on these results, we postulate that the regulation of desaturases, KPSE and LPAQ, might be key factor regulating the opposite component ratios in the two sibling moths. In addition, our study has yielded large-scale sequence information for further studies and can be used to identify potential targets for the bio-control of these species by disrupting their sexual communication.

Wilms tumor gene, Wt1, is abundantly expressed in testis Sertoli cells. Our recent study demonstrated that Wt1 is involved in spermatogenesis by regulating Sertoli cell polarity. In the present study, we found that Wt1 is also required for steroidogenesis in Leydig cells and that deletion of the Wt1 gene resulted in defects in testosterone biosynthesis and downregulation of steroidogenic gene expression, including cytochrome P450 side-chain cleavage (P450scc), steroidogenic acute regulatory protein (StAR), 3beta-hydroxysteroid dehydrogenase I (3beta-HSD), and cytochrome P450 17A1 (Cyp17a1). The expression of LHR was significantly decreased in Wt1(-/flox); Cre-ER(TM) testes after tamoxifen induction, whereas the luteinizing hormone level in serum was unchanged. Further studies revealed that desert hedgehog (Dhh) expression was regulated by Wt1 in Sertoli cells and that its expression was significantly reduced in Wt1-deficient testes. In vitro study demonstrated that the defect in testosterone production and decreased expression of several steroidogenic genes in Wt1-deficient testis explants was partially rescued by smoothened agonist (SAG), a hedgehog pathway agonist. These results indicate that Wt1 is most likely involved in Leydig cell steroidogenesis by regulating the expression of paracrine factors in seminiferous tubules. Dhh probably had important roles in this process, but we could not exclude the possibility that other factors were also required for Leydig cell steroidogenesis. Loss of Wt1 leads to downregulation of paracrine factors, which in turn causes a decrease in steroidogenic enzyme expression and reduces testosterone production in Leydig cells. The results of this study further confirm that the cross talk between Sertoli cells and Leydig cells has important roles in Leydig cell steroidogenesis.

BackgroundThe cotton aphid, Aphis gossypii Glover, is a destructive insect pest worldwide; it directly or indirectly damages (virus transmission) 300 species of host plants. Knowledge of their ecologically adaptive mechanisms at the molecular level may provide an essential and urgent method to effectively control this pest. However, no transcriptome information is available for the cotton aphid and sequence data are scarce. Therefore, we obtained transcriptome data.ResultsTo facilitate such a study, two cotton aphid transcriptomes at different growth stages of cotton, seedling and summer, were sequenced. A total of 161,396 and 66,668 contigs were obtained and assembled into 83,671 and 42,438 transcripts, respectively. After combining the raw date for both transcriptomes, the sequences were reassembled into 66,695 transcripts, and 52,160 were annotated based on BLASTX analyses. Comparison of the transcriptomes revealed that summer presented less challenges for the cotton aphids than the seedling stage of cotton. In total, 58 putative heat shock protein genes and 66 candidate cytochrome p450 genes were identified with BLASTX.ConclusionsOur results form a basis for exploring the molecular mechanisms of ecological adaption in the cotton aphid. Our study also provides a baseline for the exploration of abiotic stress responses. In addition, it provides large-scale sequence information for further studies on this species.