Wing Morphs Research Articles

Crowding leads to higher incidence of brachypterous females in the tobacco thrips, Frankliniella fusca (Hinds) (Thysanoptera: Thripidae)

• In wing-polyphenic insects, crowding generally promotes to macropter production. • Female of F. fusca exhibits wing diphenism governed by environmental conditions . • Effect of larval density on wing form determination was detected by rearing trials. • Percentage of female macropters decreased as larval density increased. • Developmental time and body length did not differ between two wing morphs. The effects of larval density on the wing form determination of female tobacco thrips, Frankliniella fusca , were investigated by rearing thrips on leaf disks at 27.5 °C. The developmental period, head width, body length, and forewing length of individuals in each wing morph were determined to assess the relationships among larval density, growth, and wing form. Data showed that higher rearing densities increased the production of female F . fusca brachypters. There was no consistent difference in the mean developmental periods between the two wing morphs or among all 5 density treatments. The body length of females tended to decrease with increasing rearing density, but there was no significant difference in body size between the two wing morphs when they were reared under the same density level.

Vestigial mediates the effect of insulin signaling pathway on wing-morph switching in planthoppers.

Wing polymorphism is an evolutionary feature found in a wide variety of insects, which offers a model system for studying the evolutionary significance of dispersal. In the wing-dimorphic planthopper Nilaparvata lugens, the insulin/insulin-like growth factor signaling (IIS) pathway acts as a 'master signal' that directs the development of either long-winged (LW) or short-winged (SW) morphs via regulation of the activity of Forkhead transcription factor subgroup O (NlFoxO). However, downstream effectors of the IIS-FoxO signaling cascade that mediate alternative wing morphs are unclear. Here we found that vestigial (Nlvg), a key wing-patterning gene, is selectively and temporally regulated by the IIS-FoxO signaling cascade during the wing-morph decision stage (fifth-instar stage). RNA interference (RNAi)-mediated silencing of Nlfoxo increase Nlvg expression in the fifth-instar stage (the last nymphal stage), thereby inducing LW development. Conversely, silencing of Nlvg can antagonize the effects of IIS activity on LW development, redirecting wing commitment from LW to the morph with intermediate wing size. In vitro and in vivo binding assays indicated that NlFoxO protein may suppress Nlvg expression by directly binding to the first intron region of the Nlvg locus. Our findings provide a first glimpse of the link connecting the IIS pathway to the wing-patterning network on the developmental plasticity of wings in insects, and help us understanding how phenotypic diversity is generated by the modification of a common set of pattern elements.

Sex-specific associations between life-history traits and a novel reproductive polymorphism in the Pacific field cricket.

Associations between heritable polymorphisms and life-history traits, such as development time or reproductive investment, may play an underappreciated role in maintaining polymorphic systems. This is because selection acting on a particular morph could be bolstered or disrupted by correlated changes in life history or vice versa. In a Hawaiian population of the Pacific field cricket (Teleogryllus oceanicus), a novel mutation (flatwing) on the X-chromosome is responsible for a heritable polymorphism in male wing structure. We used laboratory cricket colonies fixed for male wing morph to investigate whether males and females bearing the flatwing or normal-wing (wild-type) allele differed in their life-history traits. We found that flatwing males developed faster and had heavier testes than normal-wings, whereas flatwing homozygous females developed slower and had lighter reproductive tissues than normal-wing homozygous females. Our results advance our understanding of the evolution of polymorphisms by demonstrating that the genetic change responsible for a reproductive polymorphism can also have consequences for fundamental life-history traits in both males and females.

Identification and Characterization of Neuropeptides and Their G Protein-Coupled Receptors (GPCRs) in the Cowpea Aphid Aphis craccivora.

Neuropeptides are the most abundant and diverse signal molecules in insects. They act as neurohormones and neuromodulators to regulate the physiology and behavior of insects. The majority of neuropeptides initiate downstream signaling pathways through binding to G protein-coupled receptors (GPCRs) on the cell surface. In this study, RNA-seq technology and bioinformatics were used to search for genes encoding neuropeptides and their GPCRs in the cowpea aphid Aphis craccivora. And the expression of these genes at different developmental stages of A. craccivora was analyzed by quantitative real-time PCR (qRT-PCR). A total of 40 candidate genes encoding neuropeptide precursors were identified from the transcriptome data, which is roughly equivalent to the number of neuropeptide genes that have been reported in other insects. On this basis, software analysis combined with homologous prediction estimated that there could be more than 60 mature neuropeptides with biological activity. In addition, 46 neuropeptide GPCRs were obtained, of which 40 belong to rhodopsin-like receptors (A-family GPCRs), including 21 families of neuropeptide receptors and 7 orphan receptors, and 6 belong to secretin-like receptors (B-family GPCRs), including receptors for diuretic hormone 31, diuretic hormone 44 and pigment-dispersing factor (PDF). Compared with holometabolous insects such as Drosophila melanogaster, the coding genes for sulfakinin, corazonin, arginine vasopressin-like peptide (AVLP), and trissin and the corresponding receptors were not found in A. craccivora. It is speculated that A. craccivora likely lacks the above neuropeptide signaling pathways, which is consistent with Acyrthosiphon pisum and that the loss of these pathways may be a common feature of aphids. In addition, expression profiling revealed neuropeptide genes and their GPCR genes that are differentially expressed at different developmental stages and in different wing morphs. This study will help to deepen our understanding of the neuropeptide signaling systems in aphids, thus laying the foundation for the development of new methods for aphid control targeting these signaling systems.

Density-dependent sex-biased development of macroptery in a water strider.

In wing‐polymorphic insects, wing morphs differ not only in dispersal capability but also in life history traits because of trade‐offs between flight capability and reproduction. When the fitness benefits and costs of producing wings differ between males and females, sex‐specific trade‐offs can result in sex differences in the frequency of long‐winged individuals. Furthermore, the social environment during development affects sex differences in wing development, but few empirical tests of this phenomenon have been performed to date. Here, I used the wing‐dimorphic water strider Tenagogerris euphrosyne to test how rearing density and sex ratio affect the sex‐specific development of long‐winged dispersing morphs (i.e., sex‐specific macroptery). I also used a full‐sib, split‐family breeding design to assess genetic effects on density‐dependent, sex‐specific macroptery. I reared water strider nymphs at either high or low densities and measured their wing development. I found that long‐winged morphs developed more frequently in males than in females when individuals were reared in a high‐density environment. However, the frequency of long‐winged morphs was not biased according to sex when individuals were reared in a low‐density environment. In addition, full‐sib males and females showed similar macroptery incidence rates at low nymphal density, whereas the macroptery incidence rates differed between full‐sib males and females at high nymphal density. Thus complex gene‐by‐environment‐by‐sex interactions may explain the density‐specific levels of sex bias in macroptery, although this interpretation should be treated with some caution. Overall, my study provides empirical evidence for density‐specific, sex‐biased wing development. My findings suggest that social factors as well as abiotic factors can be important in determining sex‐biased wing development in insects.

Transcriptome analysis of the male polymorphisms of fig wasp species Philotrypesis tridentata

Intraspecific male polymorphism exhibiting extreme differences in morphology, behavior and life history presents good opportunities to explore adaptation mechanisms to different environments. In this study, we examined the transcriptomic differences between wingless and winged morphs of a fig wasp species Philotrypesis tridentata to investigate molecular basis to maintain polymorphisms. The winged male adults fly outside fig syconia to mate, while the wingless only stay and mate inside fig syconia where they have developed. We identified 2,391 differentially expressed genes (DEGs) with 1,396 highly expressed in winged morphs and 995 in wingless morphs. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses on the DEGs and differential alternative splicing genes and analyzed the top ten DEGs with the highest differential expression in each morph. The results showed that genes related to biosynthesis processes, lipid metabolism, energy production, flight and defense of the complex environments outside fig syconia were up-regulated in winged morphs. Genes involved in substance and energy metabolism and chemical reception were up-regulated in wingless morphs which might relate to their living inside fig syconia. The differences in highly expressed genes between two morphs prove adaptation of P. tridentata male polymorphism to different living environments.

Expression patterns and functional analysis of the short neuropeptide F and NPF receptor genes in Rhopalosiphum padi.

The short neuropeptide F (sNPF) and NPF receptor (NPFR) genes play important roles in many physiological processes. However, information on the survival-related functions of sNPF and NPFR under different stress conditions is lacking in aphids. In this study, we cloned sNPF and NPFR, and investigated the expression levels of these genes in different developmental stages, wing morphs, and stress conditions of the bird cherry-oat aphid (Rhopalosiphum padi L.), an important agricultural pest. The sNPF and NPFR transcript levels varied among developmental stages, and their expression levels in alate females were significantly higher than those in apterous females. In addition, starvation resulted in significantly increased sNPF expression, which then recovered after refeeding. Heat stress and insecticides significantly affected transcription of both genes. sNPF and NPFR knockdown in R. padi using RNA interference revealed optimal interference efficiency at 48 h post-injection. sNPF knockdown significantly decreased adult longevity, 15-d fecundity, and food intake. Additionally, mortality under starvation, insecticides, and heat stress conditions was significantly higher after injection with double-stranded sNPF in R. padi. NPFR knockdown significantly affected food intake and starvation resistance in R. padi. These results strongly indicate that sNPF plays vital roles in food intake, longevity, and reproduction in R. padi, and it can significantly affect the pest's response to stress conditions.

Spermatophore retention may accommodate sexual signal loss in Pacific field crickets

Sexual signals are gained and lost over evolutionary time. While signal gain has obvious fitness benefits, signal loss should present significant costs due to decreased mating opportunities. Just as female mating preferences can promote evolutionary gain and elaboration of sexual signals, they may also maintain signal loss. We investigated how two components of female mate choice are involved in rapid sexual signal loss in the Pacific field cricket (Teleogryllus oceanicus), in which many males have lost the ability to sing. Males that can sing (“normal-wings”) and obligately silent males (“flatwings”) coexist in Hawaiian populations. While we know that females prefer not to mate with flatwings, we tested whether females discriminate against flatwing males before copulation due to the lack of a song or something inherent about their wing morphology. We combined this assessment with a test of post-copulatory preference by presenting females with either a normal-wing or flatwing male in the presence or absence of a courtship song stimulus. Females took significantly longer to mount males in the absence of a courtship song regardless of male wing morph. This is the first evidence that females discriminate against the absence of a song during mate choice, not male wing morph. However, females retained spermatophores for equally long regardless of male wing morph and whether they heard a courtship song, suggesting no post-copulatory barriers in the absence of a song. Pre- and post-copulatory sexual selections may not operate synchronously in this system, which may help explain the success of the silent morph in wild populations. Signal loss is ubiquitous in nature, despite the associated decrease in mating opportunities. We assessed how the interaction of pre- and post-copulatory preferences may accommodate signal loss. Song attracts mates in Pacific field crickets, but some males have lost the ability to sing in response to an acoustically orienting parasitoid. We measured how long females took to mount males (pre-copulatory choice) and the length of sperm transfer, i.e., spermatophore retention time (post-copulatory choice), when presented with normal and silent males in the presence and absence of a song stimulus. Females took longer to mate in the absence of a courtship song but kept spermatophores for full sperm transfer, regardless of song presence or male type. Pre-copulatory choice in this system acts against silent males, while post-copulatory choice may not. Asynchrony between these two episodes of sexual selection may allow signal loss to persist in spite of the challenges it presents to mating.

Cell Cycle Progression Determines Wing Morph in the Polyphenic Insect Nilaparvata lugens.

SummaryWing polyphenism is a phenomenon in which one genotype can produce two or more distinct wing phenotypes adapted to the particular environment. What remains unknown is how wing pad development is controlled downstream of endocrine signals such as insulin and JNK pathways. We show that genes important in cellular proliferation, cytokinesis, and cell cycle progression are necessary for growth and development of long wings. Wing pad cellular development of the long-winged morph was characterized by a highly structured epithelial layer with microvilli-like structures. Cells of adult short wing pads are largely in the G2/M phase of the cell cycle, whereas those of long wings are largely in G1. Our study is the first to report the comparative developmental and cellular morphology and structure of the wing morphs and to undertake a comprehensive evaluation of the cell cycle genes necessary for wing development of this unique, adaptive life history strategy.

Sexual signal loss, pleiotropy, and maintenance of a male reproductive polymorphism in crickets.

Pleiotropy between male signals and female preferences can facilitate evolution of sexual communication by maintaining coordination between the sexes. Alternatively, it can favor variation in the mating system, such as a reproductive polymorphism. It is unknown how common either of these scenarios is in nature. In Pacific field crickets (Teleogryllus oceanicus) on Kauai, Hawaii, a mutation (flatwing) that segregates as a single locus is responsible for the rapid loss of song production in males. We used outbred cricket colonies fixed for male wing morph to investigate whether homozygous flatwing and normal-wing (wild-type) females differ in responsiveness to male calling song and propensity to mate when paired with either a flatwing or normal-wing male in the presence or absence of courtship song. Flatwing females were less likely to mount a male than normal-wing females. Females of both genotypes showed a preference for normal-wing males and were more likely to mate in the presence of courtship song; normal-wing females were particularly likely to mate with song. Our results show that negative pleiotropy between obligate male silence and female mating behavior can constrain the evolution of sexual signal loss and contribute to the maintenance of a male reproductive polymorphism in the wild.

MiR-147b-modulated expression of vestigial regulates wing development in the bird cherry-oat aphid Rhopalosiphum padi

BackgroundMost aphids exhibit wing polyphenism in which wingless and winged morphs produce depending on the population density and host plant quality. Although the influence of environmental factors on wing polyphenism of aphids have been extensively investigated, molecular mechanisms underlining morph differentiation (i.e. wing development /degeneration), one downstream aspect of the wing polyphenism, has been poorly understood.ResultsWe examined the expression levels of the twenty genes involved in wing development network, and only vestigial (vg) showed significantly different expression levels in both whole-body and wall-body of third instar nymphs, with 5.4- and 16.14- fold higher expression in winged lines compared to wingless lines, respectively in Rhopalosiphum padi. vg expression was higher in winged lines compared to wingless lines in third, fourth instar nymphs and adults. Larger difference expression was observed in third (21.38-fold) and fourth (20.91-fold) instar nymphs relative to adults (3.12-fold). Suppression of vg using RNAi repressed the wing development of third winged morphs. Furthermore, dual luciferase reporter assay revealed that the miR-147 can target the vg mRNA. Modulation of miR-147b levels by microinjection of its agomir (mimic) decreased vg expression levels and repressed wing development.ConclusionsOur findings suggest that vg is essential for wing development in R. padi and that miR-147b modulates its expression.

Transcriptomic Analysis Suggests Genes Expressed Stage-Independently and Stage-Dependently Modulating the Wing Dimorphism of the Brown Planthopper.

Wing dimorphism is considered as an adaptive trait of insects. Brown planthoppers (BPHs) Nilaparvata lugens, a serious pest of rice, are either macropterous or brachypterous. Genetic and environmental factors are both likely to control wing morph determination in BPHs, but the hereditary law and genes network are still unknown. Here, we investigated changes in gene expression levels between macropterous and brachypterous BPHs by creating artificially bred morphotype lines. The nearly pure-bred strains of macropterous and brachypterous BPHs were established, and their transcriptomes and gene expression levels were compared. Over ten-thousand differentially expressed genes (DEGs) between macropterous and brachypterous strains were found in the egg, nymph, and adult stages, and the three stages shared 6523 DEGs. The regulation of actin cytoskeleton, focal adhesion, tight junction, and adherens junction pathways were consistently enriched with DEGs across the three stages, whereas insulin signaling pathway, metabolic pathways, vascular smooth muscle contraction, platelet activation, oxytocin signaling pathway, sugar metabolism, and glycolysis/gluconeogenesis were significantly enriched by DEGs in a specific stage. Gene expression trend profiles across three stages were different between the two strains. Eggs, nymphs, and adults from the macropterous strain were distinguishable from the brachypterous based on gene expression levels, and genes that were related to wing morphs were differentially expressed between wing strains or strain × stage. A proposed mode based on genes and environments to modulate the wing dimorphism of BPHs was provided.

Sublethal effects of abamectin on the development, fecundity, and wing morphs of the brown planthopper Nilaparvata lugens

Abstract The brown planthopper Nilaparvata lugens negatively affects rice yield by sucking nutrients from the rice stem and spreading viruses. In this study, the effects of sublethal concentrations of abamectin on development, fecundity, and wing morphs of N. lugens were investigated. Treatment with sublethal concentrations of abamectin showed no significant effects on the developmental period of F0 nymphs. Although LC10 and LC25 treatments resulted in 10% and 25% mortality, the LC25 treatment significantly prolonged the lifespan of macropterous and brachypterous females. Abamectin-treated brachypterous females showed significantly lower fecundity than control females. Furthermore, abamectin treatment showed no significant effects on the developmental period of F1 nymphs. However, LC25 treatment significantly inhibited the fecundity of brachypterous F1 females and significantly reduced the proportion of macropterous F1 females and brachypterous F1 males. LC25 treatment showed no significant effects on the fecundity of macropterous F1 females. Considering the proportion of macropterous and brachypterous F1 females, the relative fitness of the macropterous F1 nymphs in the control, LC10, and LC25 treatment groups was 1, 1.02, and 0.84, respectively, and that of brachypterous F1 nymphs was 1, 0.79, and 0.93, respectively. Sublethal concentrations of abamectin inhibited N. lugens emergence. The present findings indicate the potential of abamectin for N. lugens field control.

Comparative transcriptional analysis provides insights of possible molecular mechanisms of wing polyphenism induced by postnatal crowding in Aphis gossypii

BackgroundAphis gossypii is a worldwide sap-sucking pest with a variety of hosts and a vector of more than 50 plant viruses. The strategy of wing polyphenism, mostly resulting from population density increasing, contributes to the evolutionary success of this pest. However, the related molecular basis remains unclear. Here, we identified the effects of postnatal crowding on wing morph determination in cotton aphid, and examined the transcriptomic differences between wingless and wing morphs.ResultsEffect of postnatal crowding on wing determination in A. gossypii was evaluated firstly. Under the density of 5 nymphs·cm− 2, no wing aphids appeared. Proportion of wing morphs rised with the increase of density in a certain extent, and peaked to 56.1% at the density of 20 nymphs·cm− 2, and reduced afterwards. Then, transcriptomes of wingless and wing morphs were assembled and annotated separately to identify potentially exclusively or differentially expressed transcripts between these two morphs, in which 3 126 and 3 392 unigenes annotated in Nr (Non-redundant protein sequence) database were found in wingless or wing morphs exclusively. Moreover, 3 187 up- and 1 880 down-regulated genes were identified in wing versus wingless aphid. Pathways analysis suggested the involvement of differentially expressed genes in multiple cellular signaling pathways involved in wing morphs determination, including lipid catabolic and metabolism, insulin, ecdysone and juvenile hormone biosynthesis. The expression levels of related genes were validated by the reverse transcription quantitative real time polymerase chain reaction (RT-qPCR) soon afterwards.ConclusionsThe present study identified the effects of postnatal crowding on wing morphs induction and demonstrated that the critical population density for wing morphs formation in A. gossypii was 20 nymphs·cm− 2. Comparative transcriptome analysis provides transcripts potentially expressed exclusively in wingless or wing morph, respectively. Differentially expressed genes between wingless and wing morphs were identified and several signaling pathways potentially involved in cotton aphid wing differentiation were obtained.

Bio-efficacy of the indigenous entomopathogenic fungus, Beauveria bassiana in conjunction with desiccant dust to control of coleopteran stored product pests

The insecticidal activity and effects of sublethal combinations of the fungus, Beauveria bassiana-IRAN441C and commercial diatomaceous earth (DE) were assessed on adult coleopterans, Callosobruchus maculatus (F.) (Chrysomelidae), and Oryzaephilus surinamensis (L.) (Silvanidae). Dry conidia and DE were applied singly or in combination. The agents produced acceptable mortality, however, results were not affected by species of host plant seeds fed to the beetles. F1 progeny reduction was notably increased in both beetle species when mixtures of the fungus and DE were each at the LC50 level. In addition to avoidance behavior, different combinations of fungus/DE dosages induced winged morphs (non-reproductive phase) in the C. maculatus population after 50 d exposure. Our results demonstrated that a combination of B. bassiana and DE resulted in high mortality of both beetle species and co-application of B. bassiana and DE is feasible in a stored product pest management program.

Transcriptome profiling of maternal stress-induced wing dimorphism in pea aphids.

Wing dimorphism, that is, wingless and winged forms, can be induced by maternal stress signals and is an adaptive response of aphids to environmental changes. Here, we investigated the ecological and molecular effects of three kinds of stress, namely crowding, predation, and aphid alarm pheromone, on wing dimorphism. These three stressors induced high proportion of up to 60% of winged morphs in offspring. Transcriptome analysis of stress‐treated female aphids revealed different changes in maternal gene expression induced by the three stressors. Crowding elicited widespread changes in the expression of genes involved in nutrient accumulation and energy mobilization. Distinct from crowding, predation caused dramatic expression changes in cuticle protein (CP) genes. Twenty‐three CP genes that belong to CP RR2 subfamily and are highly expressed in legs and embryos were greatly repressed by the presence of ladybird. By contrast, application of alarm pheromone, E‐β‐farnesene, caused slight changes in gene expression. The three factors shared a responsive gene, cuticle protein 43. This study reveals the adaptive response of aphids to environmental stresses and provides a rich resource on genome‐wide expression genes for exploring molecular mechanisms of ecological adaptation in aphids.OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.55b2b15.

<i>Tetraneura (Tetraneurella) nigriabdominalis</i> (Hemiptera: Aphidoidea) – a species extending its range in Europe, and morphological comparison with <i>Tetraneura (Tetraneura) ulmi</i>

The paper presents the first records of Tetraneura (Tetraneurella) nigriabdominalis (Sasaki, 1899) (Eriosomatinae, Eriosomatini) from Poland, an alien species that has been expanding its range northward, which is presumably connected with climate warming. Secondary hosts of this aphid are different plant species from the family Poaceae, including Zea L. Considering the steady increase in maize cultivation area in Europe, the species can become a potential threat to this cereal. We present the morphological characteristics of winged morphs developing in galls on trees from the genus Ulmus L. Those characteristics enable to distinguish this species from Tetraneura (Tetraneura) ulmi (Linnaeus, 1758), which dominates on elms in northwestern Europe. The data on the distribution of T. (T.) nigriabdominalis in Europe are also provided.

Obligately silent males sire more offspring than singers in a rapidly evolving cricket population.

How sexual traits are gained and lost in the wild remains an important question in evolutionary biology. Pacific field crickets (Teleogryllus oceanicus) in Hawaii provide an unprecedented opportunity to investigate the factors facilitating evolutionary loss of a sexual signal in real time. Natural selection from an acoustically orienting parasitoid fly drove rapid evolution of a novel, silent male morph. While silent (flatwing) males enjoy protection from the fly, they face difficulty attracting mates. We tested how offspring production varies in association with three male attributes affected by the spread of flatwing: wing morph (flatwing or normal-wing), age (flatwings should survive longer than singers) and exposure to calling song during rearing (wild populations with many flatwings lack ambient calling song). Per mating event, flatwings sired more offspring than singers and older males were mounted more quickly by females when presented with standard courtship song. Despite prior work showing that male age and acoustic experience influence sperm characteristics associated with fertilization, age and song exposure had no influence on male offspring production per mating. This represents the first evidence that the silent male morph possesses a reproductive advantage that may help compensate for precopulatory barriers to mate attraction.

MiR-34 modulates wing polyphenism in planthopper.

Polyphenism is a successful strategy adopted by organisms to adapt to environmental changes. Brown planthoppers (BPH, Nilaparvata lugens) develop two wing phenotypes, including long-winged (LW) and short-winged (SW) morphs. Though insulin receptor (InR) and juvenile hormone (JH) have been known to regulate wing polyphenism in BPH, the interaction between these regulators remains largely elusive. Here, we discovered that a conserved microRNA, miR-34, modulates a positive autoregulatory feedback loop of JH and insulin/IGF signaling (IIS) pathway to control wing polyphenism in BPH. Nlu-miR-34 is abundant in SW BPHs and suppresses NlInR1 by targeting at two binding sites in the 3’UTR of NlInR1. Overexpressing miR-34 in LW BPHs by injecting agomir-34 induces the development towards SW BPHs, whereas knocking down miR-34 in SW BPHs by injecting antagomir-34 induces more LW BPHs when another NlInR1 suppressor, NlInR2, is also suppressed simultaneously. A cis-response element of Broad Complex (Br-C) is found in the promoter region of Nlu-miR-34, suggesting that 20-hydroxyecdysone (20E) might be involved in wing polyphenism regulation. Topic application of 20E downregulates miR-34 expression but does not change wing morphs. On the other hand, JH application upregulates miR-34 expression and induces more SW BPHs. Moreover, knocking down genes in IIS pathway changes JH titers and miR-34 abundance. In all, we showed that miRNA mediates the cross talk between JH, 20E and IIS pathway by forming a positive feedback loop, uncovering a comprehensive regulation mechanism which integrates almost all known regulators controlling wing polyphenism in insects.

Identification of genes underlying phenotypic plasticity of wing size via insulin signaling pathway by network-based analysis in Sogatella furcifera

BackgroundPhenotypic plasticity is a common and highly adaptive phenomenon where the same genotype produces different phenotypes in response to environmental cues. Sogatella furcifera, a migratory pest of rice exhibits wing dimorphism, is a model insect for studying phenotypic plasticity of wing size. The Insullin-PI3K-Akt-FOXO signaling pathway plays a crucial role in the manipulation of wing size in the migratory insects. However, the regulatory mechanism via the pathway involved in wing dimorphism are still unexplored.ResultsAccompanied by special alternative splicing, genes involved in muscle contraction and energy metabolism were highly expressed in the wing hinges of macropters, demonstrating their adaptation for energy-demanding long-distance flights. Based on FOXO ChIP-Seq analysis, a total of 1259 putative target genes were observed in the wing hinges, including wing morph development, flight muscle and energy metabolism genes. An integrated gene interaction network was built by combining four heterogeneous datasets, and the IIS-PI3K-Akt-FOXO pathway was clustered in a divided functional module. In total, 45 genes in the module directly interacting with the IIS-PI3K-Akt-FOXO pathway showed differential expression levels between the two wing hinges, thus are regarded as potential Insulin pathway mediated wing dimorphism related genes (IWDRGs). Of the 45 IWDRGs, 5 were selected for verification by gene knockdown experiments, and played significant roles in the insect wing size regulation.ConclusionsWe provided valuable insights on the genetic basis of wing dimorphism, and also demonstrated that network analysis is a powerful approach to identify new genes regulating wing dimorphic development via insulin signaling pathway in the migratory insect.