Midgut Epithelial Cells Research Articles

Autophagic activity in the midgut cells of three arachnids responds selectively to different modes of overwintering in caves.

Autophagy is a highly conserved metabolic process that regulates cellular homeostasis and energy supply by degrading dysfunctional and excess cell constituents and reserve materials into products that are reused in metabolic and biosynthetic pathways. Macroautophagy is the best studied form of autophagy in invertebrates. Starvation is a common stress factor triggering autophagy in overwintering animals. In arachnids, the midgut diverticula cells perform many vital metabolic functions and are therefore critically involved in the response to starvation. Here we studied macroautophagy in three species which apply different modes for overwintering in caves: the harvestmen Gyas annulatus in diapause, Amilenus aurantiacus with ongoing ontogenesis under fasting conditions, and the spider Meta menardi, which feeds opportunistically even in winter. The main goal was to find eventual qualitative and quantitative differences in autophagic processes by inspecting TEM micrographs. In all three species, the rates of midgut epithelial cells with autophagic structures gradually increased during overwintering, but were significantly lower in G. annulatus in the middle and at the end of overwintering than in the other two species, owing to metabolic activity having been more suppressed. Decomposition of mitochondria and glycogen took place in autophagic structures in all three species. Moreover, spherite disintegration in A. aurantiacus and a special form of lipid disintegration through "lipid bubbly structures" in M. menardi indicate the crucial involvment of selective autophagy, while no specific autophagy was observed in G. annulatus. We conclude that autophagic activities support overwintering in different ways in the species studied.

Identification of a dengue 2 virus envelope protein receptor in Aedes aegypti critical for viral midgut infection

The establishment of a productive dengue virus (DENV) infection in the midgut epithelial cells of Aedes aegypti is critical for the viral transmission cycle. The hypothesis that DENV virions interact directly with specific mosquito midgut proteins was explored. We found that DENV serotype 2 (DENV2) pretreated with trypsin interacted with a single 31 kDa protein, identified as AAEL011180 by protein mass spectrometry. This putative receptor is a highly conserved protein and has orthologs in culicine and anopheline mosquitoes. We confirmed that impairing the expression of AAEL011180 in the midgut of Ae. aegypti females abolished the interaction with DENV2, and the virus also bound to immobilized recombinant purified receptor. Furthermore, recombinant DENV2 surface E glycoprotein bound to recombinant AAEL011180 with high affinity (38.2 nM) in binding kinetic analysis using surface plasmon resonance. The gene for this DENV2 E protein receptor (EPrRec) was disrupted, but since the gene is essential in Ae. aegypti, only heterozygote knockout (ΔEPrRec+/-) females could be recovered. Further reducing EPrRec mRNA expression in the midgut of ΔEPrRec+/- females by systemic dsRNA injection significantly reduced the prevalence of DENV2 midgut infection. EPrRec also interacts with heat shock protein 70 cognate 3 (Hsc70-3), and silencing Hsc70-3 expression in ΔEPrRec females also reduced the prevalence of DENV2 midgut infection.

Single-nucleus RNA sequencing reveals midgut cellular heterogeneity and transcriptional profiles in Bombyx mori cytoplasmic polyhedrosis virus infection.

The gut is not only used by insects as an organ for the digestion of food and absorption of nutrients but also as an important barrier against the invasion and proliferation of pathogenic microorganisms. Bombyx mori cytoplasmic polyhedrosis virus (BmCPV), an insect-specific virus, predominantly colonizes the midgut epithelial cells of the silkworm, thereby jeopardizing its normal growth. However, there is limited knowledge of the cellular immune responses to viral infection and whether the infection is promoted or inhibited by different types of cells in the silkworm midgut. In this study, we used single-nucleus RNA sequencing to identify representative enteroendocrine cells, enterocytes, and muscle cell types in the silkworm midgut. In addition, by analyzing the transcriptional profiles of various subpopulations in the infected and uninfected groups, we found that BmCPV infection suppresses the response of the antiviral pathways and induces the expression of BmHSP70, which plays a role in promoting BmCPV replication. However, certain immune genes in the midgut of the silkworm, such as BmLebocin3, were induced upon viral infection, and downregulation of BmLEB3 using RNA interference promoted BmCPV replication in the midgut of B. mori. These results suggest that viral immune evasion and active host resistance coexist in BmCPV-infected silkworms. We reveal the richness of cellular diversity in the midgut of B. mori larvae by single-nucleus RNA sequencing analysis and provide new insights into the complex interactions between the host and the virus at the single-cell level.

Neurotoxicity, Cytotoxicity, and Genotoxicity of Phyto-radio Synthesized Selenium Nanoparticles in Culex pipiens Complex.

Effective mosquito management strategies are crucial to minimize the number of mosquito-borne diseases. Selenium nanoparticles (SeNPs) are promising in mosquito control because they are effective and eco-friendly rather than synthetic insecticides. The current study was conducted to evaluate the impact of SeNPs on the detoxification enzymes, acetylcholine esterase (AChE), glutathione S-transferase (GST), and α-carboxyl esterase (α-CarE), in larval instars of Culex pipiens complex at the LC50 concentration. In 3rd instar larvae treated with microwave-assisted selenium nanoparticles (SeNPs-MW) and gamma-assisted selenium nanoparticles (SeNPs-G), it was found that AChE activity was significantly inhibited. On the other hand, significant increases in GST and α-CarE activities were observed. Additionally, genotoxic and ultrastructure studies of midgut epithelial cells in 3rd instar larvae revealed DNA damage and cell lysis, including destruction of the cell membrane, microvilli, and nuclei. These findings suggest that SeNPs have an adverse effect on AChE gene expression, resulting in its downregulation. This downregulation can be attributed to the formation of reactive oxygen species induced by SeNPs that can modulate the host defense mechanism leading to apoptosis and subsequent larval mortality. The present study was the first to use phyto-microwave-assisted and gamma-assisted synthesis of SeNPs which provides an eco-friendly and cost-effective solution to reduce the risk of chemical insecticides. Furthermore, an integrated pest management program (IPM) using nanocides can be successfully developed for mosquito control.

Full-Length Transcriptome Construction and Systematic Characterization of Virulence Factor-Associated Isoforms in Vairimorpha (Nosema) Ceranae.

Vairimorpha (Nosema) ceranae is a single-cellular fungus that obligately infects the midgut epithelial cells of adult honeybees, causing bee microsporidiosis and jeopardizing bee health and production. This work aims to construct the full-length transcriptome of V. ceranae and conduct a relevant investigation using PacBio single-molecule real-time (SMRT) sequencing technology. Following PacBio SMRT sequencing, 41,950 circular consensus (CCS) were generated, and 25,068 full-length non-chimeric (FLNC) reads were then detected. After polishing, 4387 high-quality, full-length transcripts were gained. There are 778, 2083, 1202, 1559, 1457, 1232, 1702, and 3896 full-length transcripts that could be annotated to COG, GO, KEGG, KOG, Pfam, Swiss-Prot, eggNOG, and Nr databases, respectively. Additionally, 11 alternative splicing (AS) events occurred in 6 genes were identified, including 1 alternative 5' splice-site and 10 intron retention. The structures of 225 annotated genes in the V. ceranae reference genome were optimized, of which 29 genes were extended at both 5' UTR and 3' UTR, while 90 and 106 genes were, respectively, extended at the 5' UTR as well as 3' UTR. Furthermore, a total of 29 high-confidence lncRNAs were obtained, including 12 sense-lncRNAs, 10 lincRNAs, and 7 antisense-lncRNAs. Taken together, the high-quality, full-length transcriptome of V. ceranae was constructed and annotated, the structures of annotated genes in the V. ceranae reference genome were improved, and abundant new genes, transcripts, and lncRNAs were discovered. Findings from this current work offer a valuable resource and a crucial foundation for molecular and omics research on V. ceranae.

Scavenger Receptor C1 Mediates Toxicity of Binary Toxin from Lysinibacillus sphaericus to Ag55 Cells.

Lysinibacillus sphaericus harboring Binary (BinA and BinB) toxins is highly toxic against Anopheles and Culex mosquito larvae. The Anopheles Ag55 cell line is a suitable model for investigating the mode of Bin toxin action. Based on the low-levels of α-glycosidase Agm3 mRNA in Ag55 cells and the absence of detectable Agm3 proteins, we hypothesized that a scavenger receptor could be mediating Bin cytotoxicity. Preliminary RNA interference knockdown of the expressed scavenger receptors, combined with Bin cytotoxicity assays, was conducted. The scavenger Receptor C1 (SCRC1) became the focus of this study, as a putative receptor for Bin toxins in Ag55 cells, and SCRBQ2 was selected as a negative control. Open reading frames encoding SCRC1 and SCRBQ2 were cloned and expressed in vitro, and polyclonal antibodies were prepared for immunological analyses. The RNAi silencing of SCRC1 and SCRBQ2 resulted in the successful knockdown of both SCRC1 and SCRBQ2 transcripts and protein levels. The cytolytic toxicity of Bin against Ag55 cells was severely reduced after the SCRC1-RNAi treatment. The phagocytic receptor protein SCRC1 mediates endocytosis of the Bin toxin into Ag55 cells, thereby facilitating its internal cytological activity. The results support a mechanism of the Bin toxin entering Ag55 cells, possibly via SCRC1-mediated endocytosis, and encourage investigations into how Bin is transferred from its bound form on the midgut epithelial cells into the epithelial endocytic system.

Ultrastructural comparison of the larval midguts between Trypoxylus dichotomus (Linnaeus, 1771) and Anomala corpulenta (Motschulsky, 1854) (Coleoptera: Scarabaeidae)

Larvae are the most important feeding and developmental stage in the life cycle of insects. Correspondingly, the larval midguts, as the primary digestive organs, undergo diverse specialization among insect lineages. Larvae of Scarabaeoidae, commomly known as white grubs, exhibit diversity on feeding habits at the familial or subfamilial level. However, the ultrastructure of larval midguts is not yet satisfactorily understood. In this study, the larval midguts of Trypoxylus dichotomus and Anomala corpulenta were compared using light and transmission electron microscopy for the first time, to uncover the ultrastructural differences between the midguts of saprophagous and phytophagous white grubs. The larval midguts of both species are tubular with three circles of the gastric caeca, and share morphological similarities in midgut epithelial cells, layers of basal lamina, and the digestive and regenerative cells. However, the midguts of the two species differ significantly in the shape of the gastric caeca and exhibit slightly differences in muscle structure. The morphology of larval midgut is related to the feeding habits.

Actinobacteria mediated synthesis of silver nanoparticles using Streptomyces diastaticus and their biological efficacy against human vector mosquitoes and agricultural insect pests

Mosquitoes and agricultural insects were harmful to both public health and crops. Prolonged use of synthetic chemical pesticides for insect pest control was associated with resistance development and negative human and ecological effects. This study investigates the larvicidal activity of Ag-NPs produced using Streptomyces diastaticus against Culex quinquefasciatus, Anopheles stephensi, Aedes aegypti, Spodoptera litura, and Plutella xylostella. UV-Vis spectroscopy, XRD, SEM-EDX, FT-IR, TEM, DLS, and Zeta potential analysis were used to characterize the biosynthesized Ag-NPs. The results showed that biosynthesized Ag-NPs were more toxic to, A. stephensi, C. quinquefasciatus, and A. aegypti with LC50 values of 15.70, 11.10, and 17.53 µg/mL, respectively. Biosynthesized Ag-NPs exhibited the highest antifeedant effects against S. litura (88.73 %) and P. xylostella (92.36 %) at 50 µg/mL concentration. The mortality bioassay revealed considerable larvicidal activity against S. litura and P. xylostella larvae at greater doses of 50 µg/mL, 80.67 and 84.05 %, respectively. Morphogenetic variations were observed on treated larvae of C. quinquefasciatus, A. aegypti, and A. stephensi, S. litura, and P. xylostella with Ag-NPs. In the present investigation the impact of Ag-NPs on the antioxidant enzymes (SOD, CAT, and GPx), the activity of each enzyme were dramatically increased with higher concentrations resulting in significant differences. The study also found that Ag-NPs inhibited the detoxifying enzyme (GST and AChE) activity of target organisms. The histological structure of the treated and untreated larvae revealed structural changes between the midgut epithelial cells. As a consequence of these findings, the S. diastaticus-mediated Ag-NPs serve as a possible, eco-friendly biopesticide and alternative to synthetic chemicals for the control of human vector mosquitoes and destructive arthropod insect pests.

Syntaxin5 is essential for survival by ensuring midgut epithelial homeostsis and regulating feeding in Locusta migratoria

Syntaxin5 (Syx5) belongs to SNAREs family, which play important roles in fusion of vesicles to target membranes. Most of what we know about functions of Syx5 originates from studies in fungal or vertebrate cells, how Syx5 operates during the development of insects is poorly understood. In this study, we investigated the role of LmSyx5 in the gut development of the hemimetabolous insect Locusta migratoria. LmSyx5 was expressed in many tissues, with higher levels in the gut. Knockdown of LmSyx5 by RNA interference (RNAi) considerably suppressed feeding in both nymphs and adults. The dsLmSyx5-injected locusts lost body weight and finally died at a mortality of 100%. Furthermore, hematoxylin-eosin staining indicated that the midgut is deformed in dsLmSyx5-treated nymphs and the brush border in midgut epithelial cells is severely damaged, suggesting that LmSyx5 is involved in morphogenesis of the midgut. TEM further showed that the endoplasmic reticulum of midgut cells have a bloated appearance. Taken together, these results suggest that LmSyx5 is essential for midgut epithelial homeostsis that affects growth and development of L. migratoria. Thus, Syx5 is a promising RNAi target for controlling L. migratoria, and even other pests.

Identification of a novel protein localized to the crystalloid of the Plasmodium ookinete

Reducing Plasmodium parasite transmission via the mosquito vector is a promising strategy for malaria control and elimination in endemic regions. In the mosquito midgut after the ingestion of an infected blood meal, malaria parasite gametes egress from erythrocytes and fertilize to develop into motile ookinetes that traverse midgut epithelial cells and transform into oocysts adjacent the basal lamina. Plasmodium ookinetes and young oocysts possess a unique organelle called the crystalloid; which has a honeycomb-like matrix structure and is indicated to be involved in sporozoite formation and maturation. In this study, we identified a novel crystalloid protein, PY17X_1113800, that is exclusively expressed in developing ookinetes. The protein possesses a signal peptide sequence, but lacks a transmembrane domain or GPI anchor signal sequence, as well as predicted adhesive domains which are characterisitic of many crystalloid proteins. The protein is highly conserved across the phylum Apicomplexa and within the greater clade Alveolata, such as Vitrella and the ciliates Paramecium and Tetrahymena, but is absent in cryptosporidia.

Bruceine D inhibits the growth of Spodoptera litura by inducing cell apoptosis in the midgut via an oxidative burst.

Spodoptera litura is one of the most harmful lepidoptera pests in China, and is difficult to control due to its strong resistance to the current frequently used insecticide species. The requirement to develop pesticides with novel toxicology mechanisms to control S. litura is urgent. The quassinoid of bruceine D display outstanding systemic properties and strong insecticidal activity against S. litura, which possess notable application potential for integrative management of S. litura, but the mechanism of toxicity remains unclear. In this study, we found that bruceine D exerts potent growth inhibitory activity against S. litura, disrupting the ecdysone and juvenile hormone titers, and causing long-term adverse effects. Association analysis between transcriptomics and metabolomics suggested that bruceine D affected the digestion and absorption capacity of S. litura larvae by inducing a strong oxidative stress response and cell apoptosis in the intestine. Further analysis demonstrated that bruceine D can inhibit the activities of digestive and antioxidant enzymes and induce malondialdehyde (MDA)and reactive oxygen species (ROS) overaccumulation in the midgut. Moreover, the protein level of Bax, cleavage caspase 3, and cytochrome c expressed in cytoplasm (cyto) were up-regulated by bruceine D, while Bcl-2 and cytochrome c expressed in mitochondria (mito) were down-regulated. In addition, there was a noticeable increase in caspase-3 protease activity. Histopathological observations revealed that bruceine D damages the structure of midgut epithelial cells and activates lysosomes, which subsequently disrupts the midgut tissue. Overall, our findings suggested that bruceine D induced excessive ROS accumulation in midgut epithelial cells. The resulting cell apoptosis disrupted midgut tissue, leading ultimately to reduced nutrient digestion and absorption in the midgut and the inhibition of larval growth. © 2024 Society of Chemical Industry.

Searching for new molecules involved in Anopheles mosquitoes' response to Plasmodium infection.

Plasmodium parasites within mosquitoes are exposed to various physiological processes, such as blood meal digestion activity, the gonotrophic cycle, and host responses preventing the entry of parasites into the midgut wall. However, when in vitro-cultured ookinetes are injected into the hemocoel of mosquitoes, Plasmodium parasites are not affected by the vertebrate host's blood contents and do not pass through the midgut epithelial cells. This infection method might aid in identifying mosquito-derived factors affecting Plasmodium development within mosquitoes. This study investigated novel mosquito-derived molecules related to parasite development in Anopheles mosquitoes. We injected in vitro-cultured Plasmodium berghei (ANKA strain) ookinetes into female and male Anopheles stephensi (STE2 strain) mosquitoes and found that the oocyst number was significantly higher in males than in females, suggesting that male mosquitoes better support the development of parasites. Next, RNA-seq analysis was performed on the injected female and male mosquitoes to identify genes exhibiting changes in expression. Five genes with different expression patterns between sexes and greatest expression changes were identified as being potentially associated with Plasmodium infection. Two of the five genes also showed expression changes with infection by blood-feeding, indicating that these genes could affect the development of Plasmodium parasites in mosquitoes.

Mechanism of the toxic effects of tetracycline on blood meal digestion in Haemaphysalis longicornis.

The extensive utilization of antibiotics in the field of animal husbandry gives rise to various concerns pertaining to the environment and human health. Here, we demonstrate that the administration of tetracycline impedes blood meal digestion in the tick Haemaphysalis longicornis. Tissue sectioning, 16S rRNA high-throughput sequencing, and transcriptome sequencing of the midgut were employed to elucidate the mechanism underlying tetracycline toxicity. The treatment group consisted of engorged female ticks that were subjected to tetracycline microinjections (75µg per tick), whereas the control group received sterile water injections. On days 2 and 4 following the injections, the tick body weight changes were assessed and the midguts were dissected and processed. Change in tick body weight in tetracycline-treated group was less than in the control group. In tetracycline-treated ticks, midgut epithelial cells were loosely connected and blood meal digestion was impaired compared to the control group. There was no significant change in midgut bacterial diversity after tetracycline treatment. On day 2 following treatment, the relative abundance of Escherichia-Shigella was significantly decreased, whereas the relative abundance of Allorhizobium was significantly increased compared to the control group. On day 4 following treatment, the relative abundance of Escherichia-Shigella, Allorhizobium, Ochrobactrum, and Acidibacter decreased significantly, whereas the relative abundance of Paraburkholderia and Pelomonas increased significantly. Tetracycline treatment also affected midgut gene expression, producing a cumulative effect wherein the differentially expressed genes (DEGs) were mostly down-regulated. KEGG enrichment pathway analysis revealed that on day 2 the up-regulated DEGs were significantly enriched in 21 pathways, including apoptosis and phagosome. Comparatively, the down-regulated DEGs were significantly enriched in 26 pathways, including N-glycan biosynthesis, lysosome, and autophagy. In contrast, on day 4 the up-regulated DEGs were significantly enriched in 10 pathways including aminoacyl-tRNA biosynthesis, ribosome biogenesis, RNA transport, and DNA replication, whereas the down-regulated differential genes were significantly enriched in 11 pathways including lysosome, peroxisome, N-glycan biosynthesis, and fatty acid synthesis. This indicates that tetracycline injection inhibited blood meal digestion by affecting midgut digestive cells, gut flora diversity, and gene expression. These findings could contribute to tick control by inhibiting blood meal digestion.

The heat shock protein Hsc70-3 mediates an anti-apoptotic response critical for Plasmodium evasion of Anopheles gambiae immunity

ABSTRACT The mosquito immune system limits Plasmodium infection and malaria transmission. Plasmodium falciparum evades the mosquito defense response by expressing the surface protein P. falciparum P47 (Pfs47) that inhibits midgut epithelial nitration by interacting with the mosquito midgut P47 receptor (P47Rec). However, the mechanism by which P47Rec suppresses caspase-mediated nitration is unknown. Here, we show that epithelial invasion by Pfs47 knockout parasites is followed by an extrusion of cells undergoing caspase-mediated apoptosis, which triggers the release of hemocyte-derived microvesicles (HdMv’s), known to promote complement activation and ookinete lysis. In contrast, invasion by P. falciparum parasites that express Pfs47 accelerates the extrusion of damaged cells and disrupts caspase activation and HdMv release. The Anopheles gambiae heat shock protein 70 cognate 3 (Hsc70-3), the ortholog of Drosophila binding immunoglobulin protein, was identified as a molecular partner of P47Rec. Silencing of Hsc70-3 promotes lysis of Pfs47 wild-type parasites through a caspase S2-dependent mechanism. The interaction of P47Rec activates a Hsc70-3-mediated anti-apoptotic response that prevents caspase activation. The interaction of P47Rec with Hsc70-3 is necessary for P. falciparum to evade the mosquito early immune responses that target the ookinete stage. IMPORTANCE Malaria transmission by Anopheles gambiae mosquitoes is very effective, in part because the parasite expresses a surface protein called Pfs47 that allows it to evade the mosquito immune system. Here we investigate how this protein changes the response of mosquito midgut epithelial cells to invasion by the parasite. Pfs47 is known to interact with P47Rec, a mosquito midgut receptor. We found that Pf47Rec inhibits caspase-mediated apoptosis by interacting with the Hsc70-3. This disrupts nitration of midgut epithelial cells invaded by the parasite and the release of hemocyte-derived microvesicles, which are critical for effective activation of the mosquito complement system that eliminates the parasite.

A knockdown gene approach identifies an insect vector membrane protein with leucin-rich repeats as one of the receptors for the VmpA adhesin of flavescence dorée phytoplasma.

The adhesion of flavescence dorée phytoplasma to the midgut epithelium cells of their insect vectors is partially mediated by the variable membrane protein A (VmpA), an adhesin which shows lectin properties. In order to identify the insect receptor for VmpA, we identified Euscelidius variegatus cell proteins interacting with recombinant VmpA-His6. The E. variegatus proteins were identified by mass spectrometry analysis of VmpA-E. variegatus protein complexes formed upon in vitro interaction assays. To assess their impact in VmpA binding, we reduced the expression of the candidate genes on E. variegatus cells in culture by dsRNA-mediated RNAi. The effect of candidate gene knockdown on VmpA binding was measured by the capacity of E. variegatus cells to bind VmpA-coated fluorescent beads. There were 13 candidate proteins possessing potential N-glycosylation sites and predicted transmembrane domains selected. The decrease of expression of an unknown transmembrane protein with leucine-rich repeat domains (uk1_LRR) was correlated with the decreased adhesion of VmpA beads to E. variegatus cells. The uk1_LRR was more expressed in digestive tubes than salivary glands of E. variegatus. The protein uk1_LRR could be implicated in the binding with VmpA in the early stages of insect infection following phytoplasmas ingestion.

Opuntia ficus-indica cladode extract is a phagostimulant agent that impairs the morphophysiology of midgut of Spodoptera frugiperda (Lepidoptera: Noctuidae) caterpillars

The fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) is a polyphagous insect whose control mainly involves the use of synthetic insecticides that can be highly toxic to non-target organisms and lead to the selection of resistant populations. This work reports the effects of the saline extract of Opuntia ficus-indica cladodes (CE) on the feeding survival and midgut morphophysiology of S. frugiperda third instar caterpillars. CE exerted a phagostimulant effect to the caterpillars but was not able to kill them. Despite of this, the midguts of caterpillars treated with CE (12.8 mg/g) showed intense disorganization of epithelium, vacuolation of the cytoplasm of columnar cells and increased size of goblet cells, as well as absence of the peritrophic membrane. The caterpillars treated with CE showed a reduction in the amount of neutral polysaccharides and protein content at the midgut epithelial cells. Together these data may indicate that the ingestion of CE in higher concentrations or by a longer period would lead the caterpillars to death or to damage in development. In conclusion, CE ingestion resulted in damage to the midgut morphology of caterpillars, with a reduction in carbohydrate and protein content.

Low concentration of indoxacarb interferes with the growth and development of silkworm by damaging the structure of midgut cells

As an important economic insect, Bombyx mori plays an essential role in the development of the agricultural economy. Indoxacarb, a novel sodium channel blocker insecticide, has been widely used for the control of various pests in agriculture and forestry, and its environmental pollution caused by flight control operations has seriously affected the safe production of sericulture in recent years. However, the lethal toxicity and adverse effects of indoxacarb on silkworm remain largely unknown. In this study, the toxicity of indoxacarb on the 5th instar larvae of silkworm was determined, with an LC50 (72 h) of 2.07 mg/L. Short-term exposure (24 h) to a low concentration of indoxacarb (1/2 LC50) showed significantly reduced body weight and survival rate of silkworm larvae. In addition, indoxacarb also led to decreased cocoon weight and cocoon shell weight, but had no significant effects on pupation, adult eclosion, and oviposition. Histopathological and ultrastructural analysis indicated that indoxacarb could severely damage the structure of the midgut epithelial cells, and lead to physiological impairment of the midgut. A total of 3883 differentially expressed genes (DEGs) were identified by midgut transcriptome sequencing and functionally annotated using GO and KEGG. Furthermore, the transcription level and enzyme activity of the detoxification related genes were determined, and our results suggested that esterases (ESTs) might play a major role in metabolism of indoxacarb in the midgut of B. mori. Future studies to examine the detoxification or biotransformation function of candidate genes will greatly enhance our understanding of indoxacarb metabolism in B. mori. The results of this study provide a theoretical basis for elucidating the mechanism of toxic effects of indoxacarb on silkworm by interfering with the normal physiological functions of the midgut.

An oral dsRNA delivery system based on chitosan induces G protein-coupled receptor kinase 2 gene silencing for Apolygus lucorum control

RNA interference (RNAi) is recognized as a new and environmentally friendly pest control strategy due to its high specificity. However, the RNAi efficiency is relatively low in many sucking insect pests, such as Apolygus lucorum. Therefore, there is an urgent need to develop new and effective ways of dsRNA delivery. Bacterially expressed or T7 synthesized dsRNA targeting a G Protein-Coupled Receptor Kinase 2 gene was mixed with chitosan in a 1:2 ratio by mass. The size of the chitosan/dsRNA nanoparticles was 69 ± 12 nm, and the TEM and AFM images showed typical spherical or ellipsoidal structures. The chitosan nanoparticles protected the dsRNA from nuclease activity, and pH and temperature-dependent degradation, and the fluorescently-tagged nanoparticles were found to be stable on the surface of green bean plants (48 h) (Phaseolus vulgaris) and were absorbed by midgut epithelial cells and transported to hemolymph. Once fed to the A. lucorum nymph, chitosan/dsRNA could effectively inhibit the expression of the G protein-coupled receptor kinase 2 gene (70%), and led to significantly increase mortality (50%), reduced weight (26.54%) and a prolonged developmental period (8.04%). The feeding-based and chitosan-mediated dsRNA delivery method could be a new strategy for A. lucorum management, providing an effective tool for gene silencing of piercing-sucking insects.

Plasmodium parasitophorous vacuole membrane protein Pfs16 promotes malaria transmission by silencing mosquito immunity

With rising cases for the first time in years, malaria remains a significant public health burden. The sexual stage of the malaria parasite infects mosquitoes to transmit malaria from host to host. Hence, an infected mosquito plays an essential role in malaria transmission. Plasmodium falciparum is the most dominant and dangerous malaria pathogen. Previous studies identified a sexual stage-specific protein 16 (Pfs16) localized to the parasitophorous vacuole membrane. Here, we elucidate the function of Pfs16 during malaria transmission. Our structural analysis identified Pfs16 as an alpha-helical integral membrane protein with one transmembrane domain connecting to two regions across parasitophorous vacuole membrane. ELISA assays showed that insect cell-expressed recombinant Pfs16 (rPfs16) interacted with Anopheles gambiae midguts, and microscopy found that rPfs16 was bound to midgut epithelial cells. Transmission-blocking assays demonstrated that polyclonal antibodies against Pfs16 significantly reduced the number of oocysts in mosquito midguts. However, on the contrary, feeding rPfs16 increased the number of oocysts. Further analysis revealed that Pfs16 reduced the activity of mosquito midgut caspase 3/7, a key enzyme in the mosquito Jun-N-terminal kinase immune pathway. We conclude that Pfs16 facilitates parasites to invade mosquito midguts by actively silencing the mosquito's innate immunity through its interaction with the midgut epithelial cells. Therefore, Pfs16 is a potential target to control malaria transmission.

Proteomics and Immune Response Differences in Apis mellifera and Apis cerana Inoculated with Three Nosema ceranae Isolates.

Nosema ceranae infects midgut epithelial cells of the Apis species and has jumped from its original host A. cerana to A. mellifera worldwide, raising questions about the response of the new host. We compared the responses of these two species to N. ceranae isolates from A. cerana, A. mellifera from Thailand and A. mellifera from France. Proteomics and transcriptomics results were combined to better understand the impact on the immunity of the two species. This is the first combination of omics analyses to evaluate the impact of N. ceranae spores from different origins and provides new insights into the differential immune responses in honeybees inoculated with N. ceranae from original A. cerana. No difference in the antimicrobial peptides (AMPs) was observed in A. mellifera, whereas these peptides were altered in A. cerana compared to controls. Inoculation of A. mellifera or A. cerana with N. ceranae upregulated AMP genes and cellular-mediated immune genes but did not significantly alter apoptosis-related gene expression. A. cerana showed a stronger immune response than A. mellifera after inoculation with different N. ceranae isolates. N. ceranae from A. cerana had a strong negative impact on the health of A. mellifera and A. cerana compared to other Nosema isolates.