Lipid homeostasis is crucial for growth and development of organisms. Several cytochrome P450 monooxygenases (CYPs) are involved in lipid metabolism. The function of Cyp311a1 in the anterior midgut as a regulator of phosphatidylethanolamine (PE) metabolism in Drosophila melanogaster has been demonstrated, as depletion of Cyp311a1 caused larval growth arrest that was partially rescued by supplying PE. In this study, we investigated the role of CYP311A1 in wing morphogenesis in Drosophila. Using the GAL4-UAS system, Cyp311a1 was selectively knocked down in the wing disc. A deformed wing phenotype was observed in flies with reduced Cyp311a1 transcripts. BODIPY and oil red O staining revealed a reduction of neutral lipids in the wing disc after the depletion of Cyp311a1. In addition, we observed an enhanced sensitivity to Eosin Y penetration in the wings of Cyp311a1 knocked-down flies. Moreover, the reduction of CYP311A1 function in developing wings does not affect cell proliferation and apoptosis, but entails disordered Phalloidin or Cadherin distribution, suggesting an abnormal cell morphology and cell cortex structure in wing epithelial cells. Taken together, our results suggest that Cyp311a1 is needed for wing morphogenesis by participating in lipid assembly and cell homeostasis.

Sri Lankan cassava mosaic virus (SLCMV) is a prominent causative agent of cassava mosaic disease in Asia and relies on the whitefly Bemisia tabaci cryptic complex for its transmission. However, the molecular mechanisms involved in SLCMV transmission by B. tabaci have yet to be understood. In this study, we identified an aminopeptidase N-like protein (BtAPN) in B. tabaci Asia II 1, an efficient vector of SLCMV, which is involved in the SLCMV transmission process. Through the use of glutathione S-transferase pull-down assay and LC-MS/MS analysis, we demonstrated the interaction between BtAPN and the coat protein (CP) of SLCMV. This interaction was further confirmed in vitro, and we observed an induction of BtAPN gene expression following SLCMV infection. By interfering with the function of BtAPN, the quantities of SLCMV were significantly reduced in various parts of B. tabaci Asia II 1, including the whole body, midgut, hemolymph, and primary salivary gland. Furthermore, we discovered that BtAPN is conserved in B. tabaci Middle East-Asia Minor 1 (MEAM1) and interacts with the CP of tomato yellow leaf curl virus (TYLCV), a begomovirus known to cause severe damage to tomato production. Blocking BtAPN with antibody led to a significant reduction in the quantities of TYLCV in whitefly whole body and organs/tissues. These results demonstrate that BtAPN plays a generic role in interacting with the CP of begomoviruses and positively regulates their acquisition by the whitefly.

The small brown planthopper (SBPH, Laodelphax striatellus) is a significant rice pest, responsible for transmitting rice stripe virus (RSV) in a persistent and propagative manner. RSV is one of the most detrimental rice viruses, causing rice stripe disease, which results in considerable loss of rice grain yield. While RNA interference and gene knockout techniques have enabled gene downregulation in SBPH, no system currently exists for the overexpression of endogenous or exogenous genes. Consequently, the development of a protein expression system for SBPH is imperative to serve as a technical foundation for pest control and gene function investigations. This study aimed to construct an expression vector using the promoter of the constitutive-expressed tubulin gene of SBPH, and promoter of human cytomegalovirus (CMV). Fluorescence experiments demonstrated that both tubulin and CMV promoter could drive green fluorescent protein (GFP) expression in SBPH, and could also facilitate the expression of a nucleocapsid protein (NP) -GFP fusion protein containing viral NP with comparable efficiency. Through expression vector optimization, we have identified that the 3 tandem CMV promoters display a significantly higher promoter activity compared with both the 2 tandem CMV promoters and the single CMV promoter. In addition, the incorporation of Star polycation nanoparticles significantly enhanced the expression efficiency in SBPH. These results provide a promising technical platform for investigating gene functions in SBPH.

Collective behaviors efficiently impart benefits to a diversity of species ranging from bacteria to humans. Fly larvae tend to cluster and form coordinated digging groups under crowded conditions, yet understanding the rules governing this behavior is in its infancy. We primarily took advantage of the Drosophila model to investigate cooperative foraging behavior. Here, we report that Drosophila-related species and the black soldier fly have evolved a conserved strategy of cluster digging in food foraging. Subsequently, we investigated relative factors, including larval stage, population density, and food stiffness and quality, that affect the cluster digging behavior. Remarkably, oxygen supply through the posterior breathing spiracles is necessary for the organization of digging clusters. More importantly, we theoretically devise a mathematical model to accurately calculate how the cluster digging behavior expands food resources by diving depth, cross-section area, and food volume. We found that cluster digging behavior approximately increases 2.2 fold depth, 1.7-fold cross-section area, and 1.9 fold volume than control groups, respectively. Amplification of food sources significantly facilitates survival, larval development, and reproductive success of Drosophila challenged with competition for limited food resources, thereby conferring trophic benefits to fitness in insects. Overall, our findings highlight that the cluster digging behavior is a pivotal behavior for their adaptation to food scarcity, advancing a better understanding of how this cooperative behavior confers fitness benefits in the animal kingdom.

The olfactory system of adult lepidopterans is among the best described neuronal circuits. However, comparatively little is known about the organization of the olfactory system in the larval stage of these insects. Here, we explore the expression of olfactory receptors and the organization of olfactory sensory neurons in caterpillars of Pieris brassicae, a significant pest species in Europe and a well-studied species for its chemical ecology. To describe the larval olfactory system in this species, we first analyzed the head transcriptome of third-instar larvae (L3) and identified 16 odorant receptors (ORs) including the OR coreceptor (Orco), 13 ionotropic receptors (IRs), and 8 gustatory receptors (GRs). We then quantified the expression of these 16 ORs in different life stages, using qPCR, and found that the majority of ORs had significantly higher expression in the L4 stage than in the L3 and L5 stages, indicating that the larval olfactory system is not static throughout caterpillar development. Using an Orco-specific antibody, we identified all olfactory receptor neurons (ORNs) expressing the Orco protein in L3, L4, and L5 caterpillars and found a total of 34 Orco-positive ORNs, distributed among three sensilla on the antenna. The number of Orco-positive ORNs did not differ among the three larval instars. Finally, we used retrograde axon tracing of the antennal nerve and identified a mean of 15 glomeruli in the larval antennal center (LAC), suggesting that the caterpillar olfactory system follows a similar design as the adult olfactory system, although with a lower numerical redundancy. Taken together, our results provide a detailed analysis of the larval olfactory neurons in P. brassicae, highlighting both the differences as well as the commonalities with the adult olfactory system. These findings contribute to a better understanding of the development of the olfactory system in insects and its life-stage-specific adaptations.

The insect gustatory system participates in identifying potential food sources and avoiding toxic compounds. During this process, gustatory receptors (GRs) recognize feeding stimulant and deterrent compounds. However, the GRs involved in recognizing stimulant and deterrent compounds in the red imported fire ant, Solenopsis invicta, remain unknown. Therefore, we conducted a study on the genes SinvGR1, SinvGR32b, and SinvGR28a to investigate the roles of GRs in detecting feeding stimulant and deterrent compounds. In this current study, we found that sucrose and fructose are feeding stimulants and the bitter compound quinine is a feeding deterrent. The fire ant workers showed significant behavior changes to avoid the bitter taste in feeding stimulant compounds. Reverse transcription quantitative real-time polymerase chain reaction results from developmental stages showed that the SinvGR1, SinvGR32b, and SinvGR28a genes were highly expressed in fire ant workers. Tissue-specific expression profiles indicated that SinvGR1, SinvGR32b, and SinvGR28a were specifically expressed in the antennae and foreleg tarsi of workers, whereas SinvGR32b gene transcripts were also highly accumulated in the male antennae. Furthermore, the silencing of SinvGR1 or SinvGR32b alone and the co-silencing of both genes disrupted worker stimulation and feeding on sucrose and fructose. The results also showed that SinvGR28a is required for avoiding quinine, as workers with knockdown of the SinvGR28a gene failed to avoid and fed on quinine. This study first identified stimulant and deterrent compounds of fire ant workers and then the GRs involved in the taste recognition of these compounds. This study could provide potential target gustatory genes for the control of the fire ant.

Juvenile hormone (JH) acts in the regulation of caste differentiation between queens and workers (i.e., with or without reproductive capacity) during vitellin synthesis and oogenesis in social insects. However, the regulatory mechanisms have not yet been elucidated. Here, we identified a highly expressed microRNA (miRNA), miR-1175-3p, in the red imported fire ant, Solenopsis invicta. We found that miR-1175-3p is prominently present in the fat bodies and ovaries of workers. Furthermore, miR-1175-3p interacts with its target gene, broad-complex core (Br-C), in the fat bodies. By utilizing miR-1175-3p agomir, we successfully suppressed the expression of the Br-C protein in queens, resulting in reduced vitellogenin expression, fewer eggs, and poorly developed ovaries. Conversely, decreasing miR-1175-3p levels led to the increased expression of Br-C and vitellogenin in workers, triggering the “re-development” of the ovaries. Moreover, when queens were fed with JH, the expression of miR-1175-3p decreased, whereas the expression of vitellogenin-2 and vitellogenin-3 increased. Notably, the suppression of fertility in queens caused by treatment with agomir miR-1175-3p was completely rescued by the increased vitellogenin expression induced by being fed with JH. These results suggest the critical role of miR-1175-3p in JH-regulated reproduction, shedding light on the molecular mechanism underlying miRNA-mediated fecundity in social insects and providing a novel strategy for managing S. invicta.

Mosquito-borne diseases (MBDs) annually kill nearly half a million people. Due to the lack of effective vaccines and drugs on most MBDs, disease prevention relies primarily on controlling mosquitoes. Despite huge efforts having been put into mosquito control, eco-friendly and sustainable mosquito-control strategies are still lacking and urgently demanded. Most mosquito-transmitted pathogens have lost the capacity of de novo nutrition biosynthesis, and rely on their vertebrate and invertebrate hosts for sustenance during the long-term obligate parasitism process. Therefore, a better understanding of the metabolic interactions between mosquitoes and pathogens will contribute to the discovery of novel metabolic targets or regulators that lead to reduced mosquito populations or vector competence. This review summarizes the current knowledge about the effects of mosquito metabolism on the transmission of multiple pathogens. We also discuss that research in this area remains to be explored to develop multiple biological prevention and control strategies for MBDs.

Insects are the host or vector of diverse viruses including those that infect vertebrates, plants, and fungi. Insect viruses reside inside their insect hosts and are vertically transmitted from parent to offspring. The insect virus–host relationship is intricate, as these viruses can impact various aspects of insect biology, such as development, reproduction, sex ratios, and immunity. Arthropod-borne viruses (arboviruses) that cause substantial global health or agricultural problems can also be vertically transmitted to insect vector progeny. Multiple infections with insect viruses and arboviruses are common in nature. Such coinfections involve complex interactions, including synergism, dependence, and antagonism. Recent studies have shed light on the influence of insect viruses on the competence of insect vectors for arboviruses. In this review, we focus on the biological effects of insect viruses on the transmission of arboviruses by insects. We also discuss the potential mechanisms by which insect viruses affect the ability of hosts to transmit arboviruses, as well as potential strategies for disease control through manipulation of insect viruses. Analyses of the interactions among insect vectors, insect viruses and arboviruses will provide new opportunities for development of innovative strategies to control arbovirus transmission.

The rice stem borer (RSB), Chilo suppressalis, a notorious rice pest in China, has evolved a high resistance level to commonly used insecticides. Tetraniliprole, a new anthranilic diamide insecticide, effectively controls multiple pests, including RSB. However, the potential resistance risk of RSB to tetraniliprole is still unknown. In this study, the tetraniliprole-selection (Tet-R) strain was obtained through 10 continuous generations of selection with tetraniliprole 30% lethal concentration (LC₃₀). The realized heritability (h²) of the Tet-R strain was 0.387, indicating that resistance of RSB to tetraniliprole developed rapidly under the continuous selection of tetraniliprole. The Tet-R strain had a high fitness cost (relative fitness = 0.53). We established the susceptibility baseline of RSB to tetraniliprole (lethal concentration at LC₅₀ = 0.727 mg/L) and investigated the resistance level of 6 field populations to tetraniliprole. All tested strains that had resistance to chlorantraniliprole exhibited moderate- to high-level resistance to tetraniliprole (resistance ratio = 27.7−806.8). Detection of ryanodine receptor (RyR) mutations showed that the Y4667C, Y4667D, I4758M, and Y4891F mutations were present in tested RSB field populations. RyR mutations were responsible for the cross-resistance between tetraniliprole and chlorantraniliprole. Further, the clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated protein 9-mediated genome-modified flies were used to study the contribution of RyR mutations to tetraniliprole resistance. The order of contribution of a single RyR mutation to tetraniliprole resistance was Y4667D > G4915E > Y4667C ≈ I4758M > Y4891F. In addition, the I4758M and Y4667C double mutations conferred higher tetraniliprole resistance than single Y4667C mutations. These results can guide resistance management practices for diamides in RSB and other arthropods.

Bumblebees are important pollinators in agricultural ecosystems, but their abundance is declining globally. There is an urgent need to protect bumblebee health and their pollination services. Bumblebees possess specialized gut microbiota with potential to be used as probiotics to help defend at-risk bumblebee populations. However, evidence for probiotic benefits on bumblebees is lacking. Here, we evaluated how supplementation with Lactobacillus melliventris isolated from bumblebee gut affected the colony development of Bombus terrestris. This native strain colonized robustly and persisted long-term in bumblebees, leading to a significantly higher quality of offspring. Subsequently, the tyrosine pathway was upregulated in the brain and fat body, while the Wnt and mTOR pathways of the gut were downregulated. Notably, the field experiment in the greenhouse revealed the supplementation of L. melliventris led to a 2.5-fold increase in the bumblebee survival rate and a more than 10% increase in the number of flowers visited, indicating a better health condition and pollination ability in field conditions. Our study represents a first screening for the potential use of the native gut member, L. melliventris, as probiotic strains in hive supplement for bumblebee breeding, which may be a practical approach to improve immunity and hive health.

Due to rapidly developed resistance, pest management relies less on pyrethroids to control economically damaging infestations of the tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois) in cotton fields of Mississippi. Yet, pyrethroid resistance remains prevalent in TPB populations. This study assessed the resistance levels in adult TPB to six common pyrethroids and acephate. Resistant TBPs were collected from wild host plants in late October after harvest in the Mississippi Delta region of the United States. Based on LC₅₀ values, the field-resistant TPBs displayed higher resistance to permethrin, esfenvalerate, and bifenthrin (approximately 30 fold) and moderate resistance to λ-cyhalothrin, β-cyfluthrin, ζ-cypermethrin, and acephate (approximately 15 fold). Further investigations showed that the inhibitors of three detoxification enzyme, triphenyl phosphate (TPP), diethyl maleate (DEM), and piperonyl butoxide (PBO) had synergistic effects on permethrin, λ-cyhalothrin, and bifenthrin in resistant TPBs. Furthermore, elevated esterase, GST, and P450 activities were significantly expressed in field-resistant TPBs. Additionally, GST and esterase were reduced after 48 h exposure to certain pyrethroids at LC₅₀ dose. The synergistic and biochemical assays consistently indicated that P450 and esterase were involved in pyrethroid detoxification in TPBs. This study provides valuable information for the continued use of pyrethroids and acephate in controlling TPBs in cotton fields in the Mississippi Delta region of the United States.

Plant pathogens can alter the behavior of their insect vectors as well as their survival and reproduction. The African psyllid, Trioza erytreae, is one of the vectors of Huanglongbing, a citrus disease caused mainly by “Candidatus Liberibacter asiaticus” (CLas). The purpose of this study was to characterize the effects of CLas on the psyllid, T. erytreae using Citrus volkamerina plants as the study system. The study focused more specifically on the CLas effects prior to and after its acquisition by the psyllid T. erytreae. Our results did not support the hypothesis that CLas effects psyllid probing behavior prior to acquisition; few differences were observed between uninfected T. erytrea feeding on CLas-infected versus control plants. On the other hand, compared to psyllids that had completed their development on control plants, the ones that had completed their development on a CLas-infected plant exhibited changes in their behavior (greater velocity), physiology (smaller mass) and biochemistry (lower water and lipid content). Altogether, our results confirm the existence of a marked postacquisition effect on the vector locomotor behavior and a minor preacquisition effect of CLas on the vector behavior, which can be partially explained by physiological and biochemical changes.

Molting and metamorphosis are important physiological processes in insects that are tightly controlled by ecdysone receptor (EcR) through the 20-hydroxyecdysone (20E) signaling pathway. EcR is a steroid nuclear receptor (SR). Several FK506-binding proteins (FKBPs) have been identified from the mammal SR complex, and are thought to be involved in the subcellular trafficking of SR. However, their roles in insects are poorly understood. To explore whether FKBPs are involved in insect molting or metamorphosis, we injected an FKBP inhibitor (FK506) into a lepidopteran insect, Spodoptera litura, and found that molting was inhibited in 61.11% of the larvae, and that the time for larvae to pupate was significantly extended. A total of 10 FKBP genes were identified from the genome of S. litura and were clustered into 2 distinct groups, according to their subcellular localization, with FKBP13 and FKBP14 belonging to the endoplasmic reticulum (ER) group and with the other members belonging to the cytoplasmic (Cy) group. All the CyFKBPs were significantly upregulated in the prepupal or pupal stages, with the opposite being observed for the ER group members. FK506 completely blocked the transfer of EcR to the nucleus under 20E induction, and significantly downregulated the transcriptional expression of many 20E signaling genes. A similar phenomenon was observed after RNA interference of 2 CyFKBPs (FKBP45 and FKBP12b), but not for FKBP13. Taken together, our data indicate that the cytoplasmic FKBPs, especially FKBP45 and FKBP12b, mediate the nuclear localization of EcR, thereby regulating the 20E signaling and ultimately affecting molting and metamorphosis in insects.