Insect Science最新文献

Water striders inhabit the elastic surface tension film of water, sharing their environment with other aquatic organisms. Their survival relies heavily on swift maneuverability and navigation around floating obstacles, which aids in the exploration of their habitat and in escaping from potential threats. Their high agility is strongly based on the ability to execute precise turns, enabling effective directional control. This paper investigates the intricate coordination of leg movements essential for initiating and sustaining turning maneuvers in water striders. We elucidate the distinct roles of each leg in modulating posture and stability during turns, with a focus on the pivotal role of the midlegs in maintaining directional movement. Through analysis of leg accelerations, decelerations, and load distribution, we unveil the spatiotemporal dynamics governing successful turns. Our findings reveal refined turning strategies employed by water striders in varying situations, from narrow to wide turns, characterized by adaptations in their locomotor system, particularly in the widening of the sculling field. Additionally, we report the phenomenon of reverse sculling, a novel escape tactic of water striders. By shedding light on the maneuverability of water striders, this study contributes to a deeper understanding of animal locomotion strategies in aquatic environments.

Feeding and molting are particularly important physiological processes for insects, and it has been reported that neuropeptides are involved in the nervous regulation of these 2 processes. Sulfakinin (SK) is an important neuropeptide that is widely distributed among insects and plays a pivotal role in regulating feeding, courtship, aggression, and locomotion. In this study, we investigated the involvement of SK in feeding and molting on a highly notorious pest insect, the fall armyworm, Spodoptera frugiperda. SK transcript levels were found in all larval stages and there was a predominant expression of SK in the brain of 5th instar larvae. By immunostaining, SK was detected in 2 pairs of cells in the median protocerebrum. But during prolonged periods of starvation, there was a significant reduction in SK messenger RNA levels; however, subsequent refeeding led to a notable increase. To investigate the role of SK in feeding and molting, SK was silenced in S. frugiperda larvae through RNA interference. This resulted in a significant increase in food intake, weight gain, and the molting process happened more rapidly in the double-stranded SK-treated larvae compared to the controls. Conversely, injection of sulfated SK peptide (sSK) caused opposite effects. Interestingly, SK-knockdown in larvae resulted in increased levels of 20-hydroxyecdysone and also of the expression of some of it signaling pathway genes. Altogether, this study highlights the important role played by SK in regulating feeding and molting in S. frugiperda.

As the catalytic subunit of the Elongator complex, Elongator protein 3 (Elp3) plays a crucial role in multiple physiological processes, including growth, development and immune responses. Previous studies on Elp3 have focused on Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens (human) or Mus musculus (mouse), whereas there are few reports on Elp3 in agricultural pests. Here, the role of TcElp3 in reproduction in the red flour beetle, Tribolium castaneum, was investigated, and the underlying mechanisms were explored. The results showed that RNA interference (RNAi)-mediated knockdown of TcElp3 in female pupae led to decreased fecundity in female adults. Consistently, the injection of dsTcElp3 into female pupae decreased the mRNA levels of the vitellogenin (Vg)-encoding genes TcVg1 and TcVg2 in female adults. Notably, knockdown of TcElp3 upregulated the expression of forkhead box protein O (FOXO) at both the mRNA and the protein level in T. castaneum, and promoted the nuclear translocation of TcFOXO. Additionally, TcElp3 directly interacts with TcFOXO and the silencing of TcElp3 significantly decreased the acetylation level of TcFOXO. Overall, our studies reveal that Elp3 regulates beetle reproduction by interacting with FOXO and modulating its acetylation status.

Succession is one of the most extensively studied ecological phenomena, yet debates persist about the importance of dispersal and external factors in driving this process. We aimed to quantify the influence of these factors by investigating how wing-related traits evolve across succession of blowfly (Diptera: Calliphoridae) communities in South Brazil. Rat carrion was placed in both forest and grassland habitats, and the associated blowfly communities were documented throughout the decomposition process. Using morphometric analysis, we measured wing and thorax traits and assessed trait changes over succession through mixed models. Our findings revealed that carrion succession follows distinct trajectories in forest and grassland environments. Specifically, we observed that Calliphora lopesi predominantly visited carcasses during the final phase of decomposition, resulting in significant differences in species composition and wing size between habitats. In forests, wing size increased toward the later stages of succession, whereas an opposite trend was observed in grasslands. Notably, these trait patterns were only evident at the species level, indicating that intraspecific trait variation is irrelevant. Stronger dispersers tend to arrive during the later stages of succession, suggesting that dispersal has a negligible role in shaping successional dynamics. Instead, environmental differences between habitats drive trait patterns throughout succession. Our results suggest that community composition in ephemeral resources is governed by deterministic processes and that successional stages can be predicted based on blowfly wing traits. Specifically, the presence of the large-winged C. lopesi indicates late decay, while the small-winged Chrysomia albiceps and Lucilia eximia are indicative of early decay.

Fungal pathogens produce secretory ribonuclease (RNase) T2 proteins during infection, which contribute to fungal virulence via their enzyme functions in degradation of host cell RNA. However, the details of those proteins entering the host cells are unclear. Our previous study demonstrated that the two secretory RNase T2 members, BbRNT2 and BbTrv, produced by the insect fungal pathogen Beauveria bassiana, caused cytotoxic damage to insect cells and contributed to fungal virulence. Here, the Spodoptera frugiperda ovarian epithelial cells (sf9 cells) were used as models to investigate the interactions of the two fungus-produced RNase T2 proteins with the insect cells. Two transmembrane proteins, an ABC transporter (SfABCG) and an Innexin 7-like protein (Sfinx), were identified from the sf9 cells as interacting with BbRNT2 and BbTrv, respectively, through protein immunoprecipitation, yeast-two hybrid tests and protein pull-down assays. Although a slight decrease in the sf9 cell viability was examined by transfection of RNA interference of SfABCG or Sfinx, the transfected cells displayed a dramatically decreased sensitivity to BbRNT2 or BbTrv, suggesting the requirement of the two transmembrane proteins for BbRNT2 and BbTrv to enter the insect cells. These results reveal a mechanism of the cytotoxic molecules, T2 RNases, produced by the fungal pathogen, entering the insect cells via interaction with specific insect cell transmembrane proteins and causing cytotoxic damage.

The regulation and maintenance of immune homeostasis are essential for animal survival, but the molecular mechanisms are not fully understood. Here, we used the model organism Drosophila melanogaster to uncover a potential mechanism by which the nuclear factor-κB transcription factor Relish and miR-100 cooperatively regulate innate immune homeostasis. We first demonstrated in vitro and in vivo that miR-100 can negatively regulate the immune responses of the Imd pathway by inhibiting the expression of TAK1-associated binding protein 2 (Tab2) gene. Second, we found that Relish, an important transcription factor in the Drosophila Imd pathway, could not only modulate the expressions of antimicrobial peptides (AMPs) to promote immune responses, but also bind to the promoter region of miR-100 and activate its transcription to inhibit immune responses. Third, the dynamic expression of genes profiling indicated that the Relish/miR-100/Tab2 regulatory axis could contribute to innate immune homeostasis in Drosophila. Together, our findings reveal the dual role of Relish in immune regulation, that is, Relish promotes the expression of AMPs to resist pathogen infection in the early immune response, while in the late immune stages, Relish readjusts the expression of miR-100 to negatively control immune responses to avoid excessive immunity thus maintaining immunohomeostasis. Meanwhile, our study provides a new perspective for further understanding the complex regulatory mechanism of immune homeostasis in animals.

Juvenile hormone (JH) plays a pivotal role in regulating post-emergence development and metabolism in previtellogenic female Aedes aegypti mosquitoes. In contrast, yolk protein precursor production and egg maturation after a blood meal are regulated by the steroid hormone 20-hydroxyecdysone, the insulin-like growth factor (IGF)/insulin signaling (IIS) pathway, and the mammalian target of rapamycin (mTOR) pathway. The role of IIS/mTOR signaling in female adults prior to blood feeding has not been thoroughly investigated. In this study, we identified a significant increase in the phosphorylation of key effector proteins in the IIS/mTOR signaling pathway, including eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), ribosomal protein S6 kinase (S6K) and forkhead box protein O1 (FoxO1), in previtellogenic females. In vitro fat body culture experiments suggest that JH induces these phosphorylations through rapid nongenomic signaling mediated by the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mTOR network. RNA interference experiments demonstrated that activation of IIS/mTOR signaling in previtellogenic females modulate metabolic gene expression, promoting the accumulation of energy reserves (glycogen and triglycerides), which influence mosquito fecundity. Additionally, depletion of either the insulin receptor (InR) or the JH receptor Methoprene-tolerant (Met) in adult mosquitoes abolished the phosphorylation of these proteins, indicating that both receptors are involved in JH-induced membrane-initiated signal transduction. Although the precise mechanisms remain unclear, this study uncovers a novel function of the IIS/mTOR pathway in adult mosquitoes before blood feeding, as well as a new mode of JH action through its crosstalk with the IIS pathway.

Tsetse flies are the sole cyclic vectors of African trypanosomes, which cause human and animal African trypanosomiases in Africa. Tsetse fly control remains a promising option for disease management. The sterile insect technique (SIT) stands as an environmentally friendly tool to control tsetse populations. SIT requires the mass-rearing of competent sterile males to mate with wild females. However, long-term colonization might affect the genetic structure of the reared flies. This study investigated the genetic structure of four Glossina palpalis gambiensis colonies of different ages: two originating from Senegal (SEN and ICIRSEN) and two from Burkina Faso (CIR and IBD). Samples from these colonies were genotyped at ten microsatellite loci, followed by downstream population genetic analyses. The results show that the two colonies from Burkina Faso collected from close sites (∼20 km apart) over 45-year interval retained the same genetic background (F_{ST_CIR∼IBD} ≈ 0, P-value = 0.47). These flies were however, genetically different from those from the Senegal colonies (F_{ST_CIR∼SEN} ≈ 0.047; F_{ST_IBD∼SEN} ≈ 0.058, P-value = 10^-4). Moreover, no significant difference was detected in the gene diversity of the CIR and IBD colonies, with H_S values of 0.650 and 0.665, respectively. The inbreeding coefficient showed that all four colonies where under Hardy-Weinberg equilibrium, with F_IS values of 0.026, 0.012, -0.064, and 0.001, for CIR, IBD, ICIRSEN, and SEN, respectively. Furthermore, no sign of a recent bottleneck was identified in tsetse samples from any of the four colonies. The results suggest that long-term mass-rearing of tsetse flies has no significant impact on their genetic background and diversity.

The tobacco cutworm Spodoptera litura is one of the most destructive polyphagous crop pests. Olfaction and taste play a crucial role in its host plant selection and sexual communication, but the expression profile of chemosensory genes remains unclear. In this study, we identified 185 chemosensory genes from 7 organs in S. litura by transcriptome sequencing, of which 72 genes were published for the first time, including 27 odorant receptors (ORs), 26 gustatory receptors (GRs), 1 ionotropic receptor (IR), 16 odorant-binding proteins (OBPs), and 2 chemosensory proteins (CSPs). Phylogenetic analyses revealed that ORs, IRs, OBPs, and sensory neuron membrane proteins (SNMPs) were mainly expressed in antennae and sequence-conserved among Noctuidae species. The most differentially expressed genes (DEGs) between sexes were ORs and OBPs, and no DEGs were found in GRs. GR transcripts were enriched in proboscis, and the expression of sugar receptors was the highest. Carbon dioxide receptors, sugar receptor-SliuGR6, and bitter GRs-SlituGR43 and SlituGR66 had higher sequence identities between Noctuidae species. CSPs were broadly expressed in various organs, and SlituCSP13 was a DEG in adult antennae. The functional analysis in the Drosophila OR67d expression system found that SlituOR50, a receptor highly expressed in female antennae, is selectively tuned to farnesyl acetate. The results provide a solid foundation for understanding the molecular mechanisms by which chemosensory genes operate to elicit behavioral responses in polyphagous insects.

The tanning hormone, Bursicon, is a neuropeptide secreted by the insect nervous system that functions as a heterodimer composed of Burs-α and Burs-β subunits. It plays a critical role in the processes of cuticle tanning and wing expansion in insects. In this study, we successfully identified the AcBurs-α and AcBurs-β genes in Aphis citricidus. The open reading frames of AcBurs-α and AcBurs-β were 480 and 417 bp in length, respectively. Both AcBurs-α and AcBurs-β exhibited 11 conserved cysteine residues. AcBurs-α and AcBurs-β were expressed during all developmental stages of A. citricidus and showed high expression levels in the winged aphids. To investigate the potential role of AcBurs-α and AcBurs-β in wing development, we employed RNA interference (RNAi) techniques. With the efficient silencing of AcBurs-α (44.90%) and AcBurs-β (52.31%), malformed wings were induced in aphids. The proportions of malformed wings were 22.50%, 25.84%, and 38.34% in dsAcBurs-α-, dsAcBur-β-, and dsAcBurs-α + dsAcBur-β-treated groups, respectively. Moreover, feeding protein kinase A inhibitors (H-89) also increased the proportion of malformed wings to 30.00%. Feeding both double-stranded RNA and inhibitors (H-89) significantly downregulated the wing development-related genes nubbin, vestigial, notch and spalt major. Silence of vestigial through RNAi also led to malformed wings. Meanwhile, the exogenous application of 3 hormones that influence wing development did not affect the expression level of AcBursicon genes. These findings indicate that AcBursicon genes plays a crucial role in wing development in A. citricidus; therefore, it represents a potential molecular target for the control of this pest through RNAi-based approaches.