Wing Morphs Research Articles

Functional evaluation of the insulin/insulin-like growth factor signaling pathway in determination of wing polyphenism in pea aphid.

Wing polyphenism is a common phenomenon that plays key roles in environmental adaptation of insects. Insulin/insulin-like growth factor signaling (IIS) pathway is a highly conserved pathway in regulation of metabolism, development, and growth in metazoans. It has been reported that IIS is required for switching of wing morph in brown planthopper via regulating the development of the wing pad. However, it remains elusive whether and how IIS pathway regulates transgenerational wing dimorphism in aphid. In this study, we found that pairing and solitary treatments can induce pea aphids to produce high and low percentage winged offspring, respectively. The expression level of ILP5 (insulin-like peptide 5) in maternal head was significantly higher upon solitary treatment in comparison with pairing, while silencing of ILP5 caused no obvious change in the winged offspring ratio. RNA interference-mediated knockdown of FoxO (Forkhead transcription factor subgroup O) in stage 20 embryos significantly increased the winged offspring ratio. The results of pharmacological and quantitative polymerase chain reaction experiments showed that the embryonic insulin receptors may not be involved in wing polyphenism. Additionally, ILP4 and ILP11 exhibited higher expression levels in 1st wingless offspring than in winged offspring. We demonstrate that FoxO negatively regulates the wing morph development in embryos. ILPs may regulate aphid wing polyphenism in a developmental stage-specific manner. However, the regulation may be not mediated by the canonical IIS pathway. The findings advance our understanding of IIS pathway in insect transgenerational wing polyphenism.

The transcription factor Zfh1 acts as a wing-morph switch in planthoppers

Insect wing polyphenism is characterized by its ability to produce two or more distinct wing morphs from a single genotype in response to changing environments. However, the molecular basis of this phenomenon remains poorly understood. Here, we identified a zinc finger homeodomain transcription factor Zfh1 that acts as an upstream regulator for the development of long-winged (LW) or shorted-winged (SW) morphs in planthoppers. Knockdown of Zfh1 directs SW-destined nymphs to develop into LW morphs by down-regulating the transcriptional level of FoxO, a prominent downstream effector of the insulin/IGF signaling (IIS) pathway. The balance between transcriptional regulation via the Zfh1-FoxO cascade and post-translational regulation via the IIS-FoxO cascade provides a flexible regulatory mechanism for the development of alternative wing morphs. These findings help us understand how phenotypic diversity is generated by altering the activity of conserved proteins, and provide an extended framework for the evolution of wing morphological diversity in insects.

Comparative transcriptional analysis and identification of hub genes associated with wing differentiation of male in Aphis gossypii

BackgroundAphis gossypii Glover (Hemiptera: Aphididae), a worldwide polyphagous phloem-feeding agricultural pest, has three wing morphs (winged parthenogenetic female, gynopara, and male) in the life cycle. The exclusive males could fly from summer hosts to winter hosts, which are essential for gene exchanges of cotton aphid populations from different hosts or regions. However, the molecular mechanism of wing differentiation of male in A. gossypii remains unclear.ResultsMorphological observation of male A. gossypii showed that there is no distinct difference in the external morphologies of the 1st and 2nd instar nymphs. The obvious differentiation of wing buds started in the 3rd instar nymph and was visible via naked eyes in the 4th instar nymphal stage, then adult male emerged with full wings. According to morphological dynamic changes, the development of wings in males were divided into four stages: preliminary stage (the 1st instar to 2nd instar), prophase (the 3rd instar), metaphase (the 4th instar), anaphase (the 5th instar). Results of feeding behavior monitoring via EPG (electrical penetration graph) technology indicated that although the male cotton aphids had strong desire to feed (longer duration of C 55.24%, F 5.05% and Pd waves 2.56%), its feeding efficiency to summer host cotton was low (shorter E1 3.56% and E2 waves 2.63%). Dynamic transcriptome analysis of male aphid at 5 different developmental periods showed that in the 3rd instar nymph, the number of up-regulated DEGs was significant increased, and time-course gene transcriptional pattern analyses results also showed that numerous genes categorized in clusters 3, 5, and 8 had the highest expressed levels, which were consistent with morphological changes of wing buds. These results indicate that the 3rd instar nymph is the critical stage of wing bud differentiation in males. Furthermore, through pathway enrichment analysis of DEGs and WGCNA, it revealed that the neuroactive ligand-receptor interaction, Ras signaling pathway, dopaminergic synapse, circadian entrainment and the corresponding hub genes of PLK1, BUB1, SMC2, TUBG, ASPM, the kinesin family members (KIF23, KIF20, KIF18-19) and the novel subfamily of serine/threonine (Aurora kinase A and Aurora kinase B) probably played an important role in the critical stage of wing bud differentiation.ConclusionThis study explored morphological changes and genes transcriptional dynamics males in cotton aphid, revealed the phenomenon of low feeding efficiency of winged males on summer host cotton, and identified key signaling pathways and potential hub genes potentially involved in wing bud differentiation of male in A. gossypii.

Assessment of Non-Consumptive Predation Risk of Coccinella septempunctata (Coleoptera: Coccinellidae) on the Population Growth of Sitobion miscanthi (Hemiptera: Aphididae).

Simple SummaryChanges in prey biology driven by predation threats that do not involve direct consumption are referred to as non-consumptive effects (NCEs). In general, NCEs are considered common and can affect herbivores sometimes stronger than the direct consumptive effects. However, how the NCEs of predators affect the development, survival, fecundity, and population growth of prey has not been well documented, which is the primary consideration for the compatibility of prey with its natural enemies in agricultural ecosystems. We examined the NCEs of the predator Coccinella septempunctata on the life-history traits and population growth of Sitobion miscanthi via caged predator (i.e., S. miscanthi co-existed with caged C. septempunctata) and caged prey (i.e., C. septempunctata co-existed with caged S. miscanthi) treatments by employing the age-stage, two-sex life table. The findings indicate that S. miscanthi could respond to the predation risk of caged predators by either accelerating the developmental rate or reducing the net reproductive rate, while S. miscanthi might reduce their fitness in response to the predation risk of caged prey. Furthermore, S. miscanthi might also increase the number of winged morphs under both of the above treatments. The results have practical ramifications on managing this economically important pest on wheat production with reduced insecticide applications.How the non-consumptive effects (NCEs) of predators influence the development, survival, fecundity, and population growth of prey has not been well documented, which is the primary consideration for the compatibility of prey with its natural enemies in agricultural ecosystems. We herein employed the age-stage, two-sex life table to examine the NCEs of the predator Coccinella septempunctata on the life-history traits and population growth of prey Sitobion miscanthi via caged predator (prey co-existing with caged predator) and caged prey (predator co-existing with caged prey) treatments with daily different exposure times (i.e., 0 h (control), 12 h, and 24 h). The results indicated that the predation risk of a caged predator could reduce the first nymphal duration and net reproductive rate (R0) of S. miscanthi at 12 h, and the first nymphal duration, preadult duration, and mean generation time (T) at 24 h. However, the predation risk of the caged prey resulted in the prolongation of the pre-adult development time and total pre-reproductive period (TPRP) as well as lowered the intrinsic rate of increase (r), finite rate of increase (𝜆), R0, life expectancy, and reproductive value of S. miscanthi after both 12 h and 24 h. Furthermore, the predation risk of both the caged predator and caged prey could increase the percent of winged morph at 24 h. These findings indicate that S. miscanthi could respond to the predation risk of the caged predator by either accelerating the developmental rate or reducing the net reproductive rate, while S. miscanthi might reduce their fitness in response to the predation risk of caged prey. Furthermore, S. miscanthi might also alter to winged morphs for dispersal under both of the above treatments. The findings obtained have practical ramifications for managing this economically important pest in wheat production with reduced insecticide applications.

No Evidence of Bacterial Symbionts Influencing Host Specificity in Aphis gossypii Glover (Hemiptera: Aphididae).

Simple SummaryThe cotton-melon aphid, Aphis gossypii Glover, is a polyphagous insect pest with many host-specialized biotypes. The mechanism of host specificity remains unknown in this aphid. In this study, we investigated whether bacterial symbionts control the host specificity of A. gossypii, as reported in some aphids. The two typical host-specialized biotypes used in this study produced significantly fewer nymphs on non-native hosts than on a native host, indicating a high host specificity of the two biotypes. We found that the winged morph of both biotypes had a significantly lower host specificity than its corresponding wingless morph. Bacterial analysis indicated that the composition of the bacterial symbionts was not different between the two biotypes, but within each biotype, the Buchnera abundance in the winged morph was only about 10% of that in the wingless morph. We suspected that a low Buchnera abundance was associated with a low host specificity. We compared the reproduction of A. gossypii with different Buchnera abundances, and did not find that a low Buchnera abundance resulted in a low host specificity. We then concluded that the host specificity of A. gossypii is not controlled by specific bacterial symbionts or Buchnera abundance.The cotton-melon aphid, Aphis gossypii Glover, is a polyphagous insect pest with many host-specialized biotypes, such as the Cucurbitaceae- and Malvaceae-specialized (CU and MA) biotypes. Bacterial symbionts were reported to determine the host range in some aphids. Whether this is the case in A. gossypii remains unknown. Here, we tested the host specificity of the CU and MA biotypes, compared the host specificity between the wingless and winged morph within the same biotype, and analyzed the composition of the bacterial symbionts. The reproduction of the CU and MA biotypes reduced by 66.67% and 82.79%, respectively, on non-native hosts, compared with on native hosts. The composition of bacterial symbionts was not significantly different between the CU and MA biotypes, with a Buchnera abundance >95% in both biotypes. Meanwhile, the winged morph produced significantly more nymphs than the wingless morph on non-native hosts, and the Buchnera abundance in the winged morph was only about 10% of that in the wingless morph. There seemed to be a relationship between the Buchnera abundance and host specificity. We regulated the Buchnera abundance by temperature and antibiotics, but did not find that a low Buchnera abundance resulted in the high reproduction on non-native hosts. We conclude that the host specificity of A. gossypii is not controlled by specific bacterial symbionts or by Buchnera abundance.

Photoperiod controls wing polyphenism in a water strider independently of insulin receptor signalling.

Insect wing polyphenism has evolved as an adaptation to changing environments and a growing body of research suggests that the nutrient-sensing insulin receptor signalling pathway is a hot spot for the evolution of polyphenisms, as it provides a direct link between growth and available nutrients in the environment. However, little is known about the potential role of insulin receptor signalling in polyphenisms which are controlled by seasonal variation in photoperiod. Here, we demonstrate that wing length polyphenism in the water strider Gerris buenoi is determined by photoperiod and nymphal density, but is not directly affected by nutrient availability. Exposure to a long-day photoperiod is highly inducive of the short-winged morph whereas high nymphal densities moderately promote the development of long wings. Using RNA interference we demonstrate that, unlike in several other species where wing polyphenism is controlled by nutrition, there is no detectable role of insulin receptor signalling in wing morph induction. Our results indicate that the multitude of possible cues that trigger wing polyphenism can be mediated through different genetic pathways and that there are multiple genetic origins to wing polyphenism in insects.

Distal leg structures of Zoraptera – did the loss of adhesive devices curb the chance of diversification?

The distal leg structures of Zoraptera are documented and discussed with respect to their functional morphology and evolutionary aspects. We investigated eight species using scanning electron microscopy. We analyzed material compositions of the tarsus in three representative species using confocal laser scanning microscopy. When possible, we included both sexes, wing morphs, and nymphs and compared the structures among them. The distal leg structure is unusually uniform across zorapterans regardless of the sex, morphs, and developmental stages. The observed features combine simplification with innovation. The former is likely partially correlated with cryptic microhabitats and miniaturization. Innovation includes a protibial cleaning organ. This is very likely an autapomorphy of Zoraptera. The tarsi are composed of two tarsomeres covered with setae. The pretarsus distally bears an unguitractor plate and well-sclerotized claws. The tarsomeres appear less-sclerotized than the covering setae. The articulation between the basitarsus and tarsomere 2 is hinge-like, implying that tarsomere 2 moves only mediolaterally. The simplified and specialized tarsal morphology is likely suitable for the typical zorapteran microhabitat, under bark. However, the irreversible complete loss of adhesive devices prevented zorapterans to make use of a broader spectrum of environments and was presumably one reason for the species paucity of the group.

Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens.

Wing dimorphism is a fascinating feature of the ability of insects to adapt to environments. The brown planthopper (BPH) Nilaparvata lugens, a serious pest of rice, can switch between the long- and short-winged morphs. It has been known that environmental factors can affect the wing morph of BPH. However, it is still unclear whether the effect of environment is dependent on BPH genetic backgrounds or not. In the present study, we established the pure-bred lineages of short- and long-winged BPHs via multigenerational selection, and we found that survival and fecundity were similar between these 2 lineages. Wing morphs of the pure-bred lineages were almost fully dependent on genetics, but independent of the environmental factors, nymphal density and rice plant stage, 2 key factors affecting BPH wing morphs. In the unselected BPH population, short- and long-winged morphs were produced depending on those 2 environmental factors, indicating the contribution of environment to wing morph. In the wing-selected lineages, 4 developmental regulated genes of wing, NlInR1, NlInR2, NlAkt, and NlFoxo were expressed stably in the short-winged adults, but almost silenced in the long-winged adults. However, all these genes were expressed normally with a similar level in both the short- and long-winged adults in an unselected population except NlFoxo. The pure-bred lineages of long- and short-winged morphs exhibited different expression patterns of wing development-regulated genes, suggesting the genetic determination of wing morphs. Effects of environmental factors on wing morphs occurred only in the genetic mix population.

Rapid Changes in Composition and Contents of Cuticular Hydrocarbons in Sitobion avenae (Hemiptera: Aphididae) Clones Adapting to Desiccation Stress.

Cuticular hydrocarbons (CHCs) are diverse in insects, and include variable classes of cuticular lipids, contributing to waterproofing for insects under desiccation environments. However, this waterproofing function of CHCs is still not well characterized in aphids. In this study, we compared CHC profiles for desiccation-resistant and nonresistant genotypes of the grain aphid, Sitobion avenae (Fabricius), in responses to desiccation. Our result showed that a total of 27 CHCs were detected in S. avenae, and linear alkanes (e.g., n-C29) were found to be the predominant components. Long-chain monomethyl alkanes were found to associate closely with water loss rates in S. avenae in most cases. Resistant genotypes of both wing morphs had higher contents of short-chain n-alkanes under control than nonresistant genotypes, showing the importance of short-chain n-alkanes in constitutive desiccation resistance. Among these, n-C25 might provide a CHC signature to distinguish between desiccation-resistant and nonresistant individuals. Compared with linear alkanes, methyl-branched CHCs appeared to display higher plasticity in rapid responses to desiccation, especially for 2-MeC26, implying that methyl-branched CHCs could be more sensitive to desiccation, and play more important roles in induced desiccation-resistance. Thus, both constitutive and induced CHCs (linear or methyl-branched) can contribute to adaptive responses of S. avenae populations under desiccation environments. Our results provide substantial evidence for adaptive changes of desiccation resistance and associated CHCs in S. avenae, and have significant implications for aphid evolution and management in the context of global climate change.

Aphis spiraecola and Aphis (Toxoptera) citricidus differently manipulate plant metabolism to gain fitness in terms of population abundance or dispersal

AbstractThe response of plant cultivars to infestation by single aphid species has been widely reported, whereas the response of plants to multiple aphid species, and the mechanisms by which various aphids benefit from the induced changes, has been largely ignored. Here we analyzed the symptoms and physiological responses of sweet orange, Citrus sinensis (L.) Osbeck (Rutaceae), as affected by Aphis spiraecola Patch and Aphis (Toxoptera) citricidus (Kirkaldy) (Hemiptera: Aphididae). We further compared the feeding behavior, population abundance, and proportion of winged morph of the two aphid species when separately feeding on sweet orange. Results showed that feeding by A. spiraecola, but not A. citricidus, caused leaf curling, reduced shoot length, shoot fresh weight, and chlorophyll concentration. In addition, A. spiraecola feeding increased the concentration of essential amino acids in leaves when compared with A. citricidus and uninfested control plants. Electrical penetration graph‐studies showed that A. citricidus gained faster access and acceptance of phloem, and spent more time ingesting phloem sap, than A. spiraecola. Furthermore, after 2 weeks of infestation, A. spiraecola produced more winged morphs, whereas A. citricidus achieved higher population abundance. Thus, our results indicate that the two citrus aphids utilize divergent strategies to manipulate host metabolism, and gain fitness benefits in population abundance or winged form production. The results could improve our understanding of varied adaptive strategies of co‐existing insects and extend our knowledge of aphid‐plant interactions.

Selection of Reference Genes for RT-qPCR Analysis of Wing Dimorphism in English Grain Aphid, Sitobion avenae (Hemiptera: Aphididae).

The English grain aphid, Sitobion avenae (Fabricius), exhibits classic and dramatic phenotypic plasticity in wing development. Both genetic and environmental inputs contribute to the wing polyphenism in aphids, an extreme form of phenotypic plasticity in which a single genotype produces discrete winged and wingless morphs. Validated reference genes are needed to accurately normalize temporal and spatial variation in gene expression estimates by RT-qPCR. In this research, the stability of 11 candidate reference genes selected from S. avenae transcriptomes was evaluated under an array of abiotic and biotic conditions relevant to wing development. RefFinder, a comprehensive software integrating rankings from delta Ct, BestKeeper, NormFinder, and geNorm, offered a series of reference genes for every experimental condition. Overall, helicase (HEL) and ubiquitin ribosomal protein S27A fusion protein (RpS27) are suited for most of the conditions examined in this study, although exceptions do exist. Specifically, NADH dehydrogenase (Ap-NADH) and 28S ribosomal RNA (28S) are recommended for insecticide and antibiotic treatments, while ribosomal RNA L14 (RPL14) and 18S ribosomal RNA (18S) are selected for density treatment, respectively. This study provides a suite of reference genes to investigate the wing polyphenism in S. avenae, and is important for application of RT-qPCR in future experiments of novel tactics to control aphids.

Novel Temporal Expression Patterns of EBF-Binding Proteins in Wing Morphs of The Grain Aphid Sitobion miscanthi.

High chemosensitivity of insects to volatile organic compounds (VOC) stimuli is mediated by odorant binding proteins (OBPs). In aphids, three OBPs (OBP3, OBP7 and OBP9) are E-β-farnesene (EBF)-binding proteins. Winged aphids are generally more sensitive than wingless aphids to VOCs, thus, wing presence is a phenotypic correlate of olfaction sensitivity. Here, we investigate the detailed temporal expression of these EBF-binding proteins and two other OBPs (OBP6 and OBP10), in the grain aphid Sitobion miscanthi 0 h, 2 h, 1 day, 3 days, 10 days, and 20 days after adult emergence. Both winged and wingless aphids were examined to further uncover phenotypic specification. Then, the expression patterns before and after EBF induction were analyzed. Throughout adulthood, only OBP7 had significantly higher antennal expression in winged aphids; however, there was no significant difference in the antennal expression of OBP3 between wing morphs at most time points. Except it was lower in newly emerged winged aphids but increased rapidly to the same level in wingless aphids at 1 day. OBP9 did not differ in expression between the morphs and was the only OBP that did not exhibit an expression trough at the beginning of the adult stage (0 h). The expression of OBP9 remained relatively stable and high throughout the adult stage in both phenotypes, showing the highest level among the three EBF-binding proteins. After EBF induction, its expression was further up-regulated in both morphs. Therefore, this protein may be an important molecule for EBF recognition in aphids. OBP7 strongly responded to EBF but only in winged aphids, suggesting that this protein is important in the more sensitive EBF recognition process of winged aphids. In addition, the antennal expression level of OBP3 did not respond to EBF induction. These findings revealed a temporal expression pattern of OBPs in aphids and showed that figuring out the pattern is critical for correctly selecting morphs and sampling times, which will support the discovery of reliable findings and allow solid conclusions to be drawn. Our findings also inspire on the interaction mode of the three EBF-binding proteins in relation to EBF perception in aphids.

Morph-specific life-history correlations in a wing-dimorphic water strider.

Life-history theory predicts a negative correlation between reproduction and survival because individuals differ in their investment in early reproduction at the expense of survival. However, life-history trade-offs can be masked when individual differences in resource allocation are smaller than those in resource acquisition. In polymorphic species, as distinct morphs exhibit differences in intrinsic physiology, the relative effects of resource acquisition and allocation on life-history traits will differ between morphs, contributing to morph-specific life-history correlations. Here, in the wing-dimorphic water strider Aquarius paludum, we found that wing morphs differed in within-morph individual-level life-history correlations. Longer-lived flight-capable long-winged females produced fewer eggs per day and matured later, whereas life-history trade-offs were not observed in short-winged flightless females. The survival-reproduction trade-off observed in long-winged females may be a result of individual differences in the timing of wing muscle histolysis. Individuals that underwent wing histolysis early would have increased reproduction at the expense of a shorter life, whereas individuals with late wing histolysis would have reduced reproduction but a longer life. Short-winged females, who never develop wings, effectively have more resources to allocate to both survival and reproduction, masking any life-history trade-offs. Thus, we suggest that morph-specific effects of resource allocation trade-offs can shape the morph-specific extent of individual variation in life-history strategies, which may contribute to the evolution and maintenance of within-species polymorphism.

Body condition indices are better surrogates for lean mass and water content than for body fat content in an insect

AbstractEcologists and evolutionary biologists often use body condition indices (BCIs) to approximate an animal’s energetic state, which is important because energy (typically, lipid) reserves influence an animal’s investment into fitness‐related traits. A BCI’s utility is typically assessed by examining its ability to predict standardized fat content (fat mass in fresh mass after correcting for body size) across a population. Less frequently, a BCI is assessed as a response variable by comparing its sensitivity to a particular treatment or factor (e.g. food availability or age) relative to that of standardized fat content. We assessed five common BCIs (or equivalent) with these two approaches in the wing‐dimorphic sand field cricket (Gryllus firmus Scudder 1902). All of the BCI methods significantly predicted standardized fat content in both sexes and wing morphs where the scaled mass index and Que ́telet’s index explained the most and least amount of variation, respectively. The BCIs and fat content were also similarly affected by adult age. However, BCIs were universally better proxies for lean mass and water content than for fat content. The relationships between BCIs and standardized lean mass and water content were stronger than those between BCIs and standardized fat content, and the effect sizes of age on BCIs were closer to that of lean mass relative to that of fat content. Thus, although BCIs reasonably predicted energy (fat) stores in G. firmus, they may be more indicative of lean mass or water content in insects. If BCIs are surrogates for protein and water storage, they may still approximate the storage of resources that fuel fitness‐related traits. Yet, future work is required to understand which body components (e.g. fat, protein or water) are most tightly linked to fitness, and whether traditional BCIs explain variation in fitness‐related body components across animal taxa.

Non-consumptive effects of the zigzag ladybird beetle, Cheilomenes sexmaculata (Fab.) on its prey, the cotton aphid, Aphis gossypii Glover

ABSTRACT Non-consumptive effects (NCEs) of predators include non-lethal changes in prey altering their behaviour and physiology with increased oxidative stress under predation-risk. Although prey species may exhibit a complex of antioxidant mechanisms, these may be inadequate to result in a reduction of adverse biological consequences in the prey. Reduced prey fitness may result and could contribute to enhancing biological control. Cotton aphid, Aphis gossypii is an important polyphagous pest predated by a variety of coccinellids and very much preferred by zigzag ladybird beetle, Cheilomenes sexmaculata (F.). Possible NCEs of C. sexmaculata on cotton aphid were studied to understand the underlying anti-oxidative mechanisms. We found that the non-consumptive effect is induced by olfactory cues, and even short-duration exposure could raise antioxidant enzyme levels in the cotton aphid. Aphids antioxidant mechanism uses upregulation of superoxide dismutase (SOD) and catalase (CAT) but not sufficiently to offset the oxidative damage that led to increased Malondialdehyde (MDA) content. Affected aphid biology with reduced reproductive performance as recorded 30.0 ± 4.40 nymphs/female under predation-risk compared to no-predation (41.6 ± 5.60). Further, the induction of winged morphs increased with active predation (21.53 ± 1.05%) and increased risk of predation (18.28 ± 4.86%) compared to aphids not exposed to predators (6.00 ± 2.99%). Antioxidant production costs were compensated by the exposed aphids directly through reduced reproduction and also triggered winged morphs in progeny. Non-consumptive effect might directly contribute to declines in aphid populations through reduced reproduction and may also stimulate dispersal of winged morphs.

Seamless Active Morphing Wing Simultaneous Gust and Maneuver Load Alleviation

This paper deals with the simultaneous gust and maneuver load alleviation problem of a seamless active morphing wing. The incremental nonlinear dynamic inversion with quadratic programming control allocation and virtual shape functions (denoted as INDI-QP-V) is proposed to fulfill this goal. The designed control allocator provides an optimal solution while satisfying actuator position constraints, rate constraints, and relative position constraints. Virtual shape functions ensure the smoothness of the morphing wing at every moment. In the presence of model uncertainties, external disturbances, and control allocation errors, the closed-loop stability is guaranteed in the Lyapunov sense. Wind tunnel tests demonstrate that INDI-QP-V can make the seamless wing morph actively to resist “1-cos” gusts and modify the spanwise lift distribution at the same time. The wing root shear force and bending moment have been alleviated by more than 44% despite unexpected actuator fault and nonlinear backlash. Moreover, during the experiment, all the input constraints were satisfied, the wing shape was smooth all the time, and the control law was executed in real time. Furthermore, as compared with the linear quadratic Gaussian control, the hardware implementation of INDI-QP-V is easier; the robust performance of INDI-QP-V is also superior.

Transcriptome Analysis of the Regulatory Mechanism of FoxO on Wing Dimorphism in the Brown Planthopper, Nilaparvata lugens (Hemiptera: Delphacidae).

Simple SummaryThe brown planthopper (BPH) Nilaparvata lugens can develop into either long-winged or short-winged adults depending on environmental stimuli received during larval stages. The transcription factor NlFoxO serves as a key regulator determining alternative wing morphs in BPH, but the underlying molecular mechanism is largely unknown. Here, we investigated the transcriptomic profile of forewing and hindwing buds across the 5th-instar stage, the wing-morph decision stage. Our results indicated that NlFoxO modulated the developmental plasticity of wing buds mainly by regulating the expression of cell proliferation-associated genes.The brown planthopper (BPH), Nilaparvata lugens, can develop into either short-winged (SW) or long-winged (LW) adults according to environmental conditions, and has long served as a model organism for exploring the mechanisms of wing polyphenism in insects. The transcription factor NlFoxO acts as a master regulator that directs the development of either SW or LW morphs, but the underlying molecular mechanism is largely unknown. Here, we microinjected SW-destined morphs with double stranded-RNA (dsRNA) targeting NlFoxO (dsNlFoxO) to change them into LW-winged morphs. In parallel, SW-destined morphs microinjected with dsRNA targeting the gene encoding green fluorescence protein (dsGfp) served as a negative control. The forewing and hindwing buds of 5th-instar nymphs collected at 24, 36, and 48 h after eclosion (hAE) were used for RNA sequencing. We obtained a minimum of 43.4 million clean reads from forewing and hindwing buds at a single developmental time. Differentially expressed genes (DEGs) were significantly enriched in various Gene Ontology (GO) terms, including cellular process, binding, and cell part. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis showed that up-regulated genes in dsNlFoxO-treated forewing and hindwing buds were largely associated with the cell cycle and DNA replication. Furthermore, most up-regulated genes displayed higher expression at 24-, and 36-hAE relative to 48 hAE, indicating that wing cells in LW-destined wings might actively proliferate during the first 36 h in 5th-instar nymphs. Our findings indicated that LW development in BPH was likely dependent on the duration of cell proliferation in the 5th-instar stage, which sheds light on the molecular basis of wing polymorphism in insects.

Temporal analysis of microRNAs associated with wing development in the English grain aphid, Sitobion avenae (F.) (Homoptera: Aphidiae)

Molecular mechanisms underlying wing evolution and development have been a point of scientific inquiry for decades. Phloem-feeding aphids are one of the most devastating global insect pests, where dispersal of winged morphs lead to annual movements, migrations, and range expansions. Aphids show a polyphenic wing dimorphism trait, and offer a model to study the role of environment in determining morphological plasticity of a single genotype. Despite recent progresses in the genetic understanding of wing polyphenism, the influence of environmental cues remains unclear. To investigate the involvement of miRNAs in wing development, we sequenced small RNA libraries of the English grain aphid, Sitobion avenae (F.) across six different developmental stages. As a result, we identified 113 conserved and 193 S. avenae-specific miRNAs. Gene Ontology and KEGG pathway analyses of putative target mRNAs for the six differentially expressed miRNAs are enriched for wing development processes. Dietary uptake of miR-263a, miR-316, and miR-184a agomirs and antagomirs led to significantly higher mortality (>70%) and a lower proportion of winged morphs (<5%). On the other hand, wing malformation was observed in miR-2 and miR-306 agomirs and miR-2 and miR-14 antagomirs, respectively, suggesting their involvement in S. avenae wing morphogenesis. These combined results not only shed light on the regulatory role of miRNAs in wing dimorphism, but also provide potential novel targets for the long-term sustainable management of S. avenae, a devastating global grain pest.

Environmental Factors Predicting Dispersal Mode of the Wing-Dimorphic Psammophilous Beetle Mecynotarsus niponicus Lewis, 1895 (Coleoptera: Anthicidae) in a Sandy Floodplain: An Exploratory Analysis

Wing-dimorphic insects occur in diverse habitats in heterogeneous environments. However, little is known about the wing dimorphism of insects that inhabit floodplains and the possible environmental factors affecting their wing morphs. In this study, we used cantharidin-baited traps to collect and quantify the psammobiont beetle Mecynotarsus niponicus Lewis, 1895 (Anthicidae) in a sandy floodplain of the Tamagawa River, Japan, in a one-year repeated cross-sectional study design. Our analysis of the demographic characteristics of over 400 M. niponicus adults and public weather-related data showed that: 1) two distinct wing morphs, long-winged (macropterous) and short-winged (brachypterous) individuals, were present within the population; 2) macroptery rates were consistently lower but varied greatly (6.7–50.0%) within a year; and 3) higher macroptery was significantly associated with greater fluctuation in river water level, namely flooding (odds ratio, 2.96; 95% confidence interval, 1.78–4.91; P < 0.001). Thus, the macropterous form of M. niponicus may be advantageous in avoiding temporal habitat loss due to river flooding. These observations may represent a first step toward testing a flooding-dispersal hypothesis for the morph alteration of wing-dimorphic insects in floodplains.

Insights into wing dimorphism in worldwide agricultural pest and host-alternating aphid Aphis gossypii

BackgroundThe worldwide pest Aphis gossypii has three-winged morphs in its life cycle, namely, winged parthenogenetic female (WPF), winged gynopara (GP), and winged male, which are all produced by a wingless parthenogenetic female (WLPF). Most studies on A. gossypii have focused on WPF, while few have investigated GP and male. The shared molecular mechanism underlying the wing differentiation in the three wing morphs of A. gossypii remains unknown. The wing differentiation of WPF was explored in a previous study. Herein, GP and male were induced indoors. The characters of the body, internal genitals, wing veins, and fecundity of GP and male were compared with those of WPF or WLPF. Compared with WLPF, the shared and separate differentially expressed genes (DEGs) were identified in these three-wing morphs.ResultsNewly-born nymphs reared in short photoperiod condition (8 L:16D, 18 °C) exclusively produced gynoparae (GPe) and males in adulthood successively, in which the sex ratio was GP biased. A total of 14 GPe and 9 males were produced by one mother aphid. Compared with WLPF, the three-wing morphs exhibited similar morphology and wing vein patterns but were obviously discriminated in the length of fore- and underwings, reproductive system, and fecundity. A total of 37 090 annotated unigenes were obtained from libraries constructed using the four morphs via RNA sequencing (RNA-Seq). In addition, 10 867 and 19 334 DEGs were identified in the pairwise comparison of GP versus WLPF and male versus WLPF, respectively. Compared with WLPF, the winged morphs demonstrated 2 335 shared DEGs (1 658 upregulated and 677 downregulated). The 1 658 shared upregulated DEGs were enriched in multiple signaling pathways, including insulin, FoxO, MAPK, starch and sucrose metabolism, fatty acid biosynthesis, and degradation, suggesting their key roles in the regulation of wing plasticity in the cotton aphid. Forty-four genes that spanned the range of differential expression were chosen to validate statistical analysis based on RNA-Seq through the reverse transcription quantitative real time polymerase chain reaction (RT-qPCR). The comparison concurred with the expression pattern (either up- or downregulated) and supported the accuracy and reliability of RNA-Seq. Finally, the potential roles of DEGs related to the insulin signaling pathway in wing dimorphism were discussed in the cotton aphid.ConclusionsThe present study established an efficiently standardized protocol for GP and male induction in cotton aphid by transferring newly-born nymphs to short photoperiod conditions (8 L:16D, 18 °C). The external morphological characters, especially wing vein patterns, were similar among WPFs, GPe, and males. However, their reproductive organs were strikingly different. Compared with WLPF, shared (2 335) and exclusively (1 470 in WLPF, 2 419 in GP, 10 774 male) expressed genes were identified in the three-wing morphs through RNA-Seq, and several signaling pathways that are potentially involved in their wing differentiation were obtained, including insulin signaling, starch and sucrose metabolism.