Metagenomic profiling of gut microbiota in Fall Armyworm (Spodoptera frugiperda) larvae fed on different host plants.

BACKGROUND: The fall armyworm (FAW, Spodoptera frugiperda) is a polyphagous pest known for causing significant crop damage. The gut microbiota plays a pivotal role in influencing the biology, physiology and adaptation of the host. However, understanding of the taxonomic composition and functional characteristics of the gut microbiota in FAW larvae fed on different host plants remains limited. METHODS: This study utilized metagenomic sequencing to explore the structure, function and antibiotic resistance genes (ARGs) of the gut microbiota in FAW larvae transferred from an artificial diet to four distinct host plants: maize, sorghum, tomato and pepper. RESULTS: The results demonstrated significant variations in gut microbiota structure among FAW larvae fed on different host plants. Firmicutes emerged as the dominant phylum, with Enterococcaceae as the dominant family and Enterococcus as the prominent genus. Notably, Enterococcus casseliflavus was frequently observed in the gut microbiota of FAW larvae across host plants. Metabolism pathways, particularly those related to carbohydrate and amino acid metabolism, played a crucial role in the adaptation of the FAW gut microbiota to different host plants. KEGG orthologs associated with the regulation of the peptide/nickel transport system permease protein in sorghum-fed larvae and the 6-phospho-ß-glucosidase gene linked to glycolysis/gluconeogenesis as well as starch and sucrose metabolism in pepper-fed larvae were identified. Moreover, the study identified the top 20 ARGs in the gut microbiota of FAW larvae fed on different host plants, with the maize-fed group exhibiting the highest abundance of vanRC. CONCLUSIONS: Our metagenomic sequencing study reveals significant variations in the gut microbiota composition and function of FAW larvae across diverse host plants. These findings underscore the intricate co-evolutionary relationship between hosts and their gut microbiota, suggesting that host transfer profoundly influences the gut microbiota and, consequently, the adaptability and pest management strategies for FAW.

Efficient CRISPR-mediated genome editing can be initiated by embryonic injection but not by ovarian delivery in the beetle Tribolium castaneum.

The clustered regularly interspaced small palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 (Cas9)-mediated gene editing technology has revolutionized the study of fundamental biological questions in various insects. Diverse approaches have been developed to deliver the single-guide RNA (sgRNA) and Cas9 to the nucleus of insect embryos or oocytes to achieve gene editing, including the predominant embryonic injection methods and alternative protocols through parental ovary delivery. However, a systematic comparative study of these approaches is limited, especially within a given insect. Here, we focused on revealing the detailed differences in CRISPR/Cas9-mediated gene editing between the embryo and ovary delivery methods in the beetle Tribolium castaneum, using the cardinal and tyrosine hydroxylase (TH) as reporter genes. We demonstrated that both genes could be efficiently edited by delivering Cas9/sgRNA ribonucleoproteins to the embryos by microinjection, leading to the mutant phenotypes and indels in the target gene sites. Next, the Cas9/sgRNA complex, coupled with a nanocarrier called Branched Amphiphilic Peptide Capsules (BAPC), were delivered to the ovaries of parental females to examine the efficacy of BAPC-mediated gene editing. Although we observed that a small number of beetles' progeny targeting the cardinal exhibited the expected white-eye phenotype, unexpectedly, no target DNA indels were found following subsequent sequencing analysis. In addition, we adopted a novel approach termed "direct parental" CRISPR (DIPA-CRISPR). However, we still failed to find gene-editing events in the cardinal or TH gene-targeted insects. Our results indicate that the conventional embryonic injection of CRISPR is an effective method to initiate genome editing in T. castaneum. However, it is inefficient by the parental ovary delivery approach.

Efficient CRISPR/Cas9-mediated ebony gene editing in the greater wax moth Galleria mellonella.

The greater wax moth, Galleria mellonella (Lepidoptera, Pyralidae), is a major bee pest that inflicts considerable harm on beehives, leading to economic losses. It also serves as a valuable resource insect and a model organism. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system plays a crucial role in improving economic insect breeding and developing efficient agricultural pest management systems in Lepidoptera. However, the CRISPR/Cas9 protocols have not been developed for G. mellonella. Here, the Gmebony knockout (KO) strain was established using the CRISPR/Cas9 genome editing system. We obtained Gmebony KO strain in the G4 generation, which took approximately 10 months. When compared with wild-type, the head, notum, and the terminal abdominal surface of 1st to 4th instar larvae in the KO strain changed from yellow to brown, and these regions of the KO strain gradually transformed into a black color from the 5th instar larvae, and the body color of the adult moth in the KO strain changed to black. The developmental period of the early larval and the following larval instars extended. The embryonic hatchability of the Gmebony KO strain was significantly decreased. The pupal body weight of the Gmebony KO strain was not affected. The feasibility of the CRISPR/Cas9 methodology was validated by single-target editing of Gmebony. Our findings provide the first evidence that the ebony gene can serve as a pigmentation reference gene for genetic modifications of G. mellonella. Meanwhile, it can be utilized in the development of genome editing control strategies and for gene function analyses in G. mellonella.

The ATP-binding cassette transporter subfamily G member 4 mediates cuticular hydrocarbon transport to regulate drought tolerance in Acyrthosiphon pisum.

ABC transporters are a highly conserved membrane protein class that promote the transport of substances across membranes. Under drought conditions, insects primarily regulate the content of cuticular hydrocarbon (CHC) to retain water and prevent evaporative loss. Involvement of ABC transporter protein G (ABCG) subfamily genes in insect CHC transport has been relatively understudied. In this study, we demonstrated that ABCG4 gene in Acyrthosiphon pisum (ApABCG4) is involved in CHC transport and affects drought tolerance by regulating CHC accumulation. ApABCG4 is strongly expressed in the abdominal cuticle and embryonic stages of A. pisum. Effective silencing of ApABCG4 was achieved using RNAi, and the silencing duration was analyzed. ApABCG4 silencing resulted in a significant decrease in the total and component contents of the CHC and cuticular waxy coatings of A. pisum. Nevertheless, the internal hydrocarbon content remained unchanged. The lack of cuticular hydrocarbons significantly reduced the drought tolerance of A. pisum, shortening its survival time under drought stress. Drought stress caused significant upregulation of ApABCG4. Molecular docking showed that ApABCG4 has a high binding affinity for nine n-alkanes of CHC through electrostatic interactions. These results indicate that ApABCG4 is a novel RNAi target with key applications in aphid biological control.

Effect of Cotesia ruficrus Parasitization on Diversity and Community Composition of Intestinal Bacteria in Spodoptera frugiperda.

Parasitoids have the potential to alter the gut microbiota of their host insects post-parasitization, thereby influencing the host's physiological functions and creating a more favorable environment for the survival of the parasitoid's progeny. Cotesia ruficrus is a native enemy of the important invasive fall armyworm (FAW) pest, Spodoptera frugiperda, in China, exhibiting significant pest control capabilities. To investigate the impact of C. ruficrus on the gut bacteria of FAW caterpillars following parasitism, we used 16S rRNA sequencing technology to analyze the diversity and richness of gut bacteria in both long-term laboratory and short-term laboratory FAW caterpillars. The results revealed Enterococcus as the predominant bacteria across all treatments, while no significant differences were observed in the diversity and richness of gut bacteria between non-parasitized and parasitized long-term laboratory FAW caterpillars. Similarly, while the diversity of gut bacteria in non-parasitized and parasitized short-term laboratory FAWs showed no significant variance, a marked discrepancy in richness was noted. Moreover, the richness of gut bacteria in short-term laboratory FAW caterpillars surpassed that of their long-term laboratory counterparts. In addition, it was found that Corynebacterium existed only in the intestinal tract of FAW caterpillars that were parasitized by C. ruficrus. These results substantiate that C. ruficrus parasitization can alter the gut microbiota of FAW caterpillars, providing valuable insights into the interplay between gut microbiota and the dynamics of parasitoid-host interactions.

In vivo functional analysis of the cotton bollworm Helicoverpa armigera 24-dehydrocholesterol reductase (HaDHCR24) in phytosterol metabolism.

Insects have to obtain sterols from food due to the inability to synthesize this essential nutrient de novo. For lepidopteran insects, they can convert a variety of phytosterols into cholesterol to meet their growth needs. The final step of the cholesterol biosynthesis is the metabolism of desmosterol catalyzed by 24-dehydrocholesterol reductase (DHCR24). In this study, we identified a DHCR24 homolog in the cotton bollworm Helicoverpa armigera, designated as H. armigera 24-dehydrocholesterol reductase (HaDHCR24)-1. The quantitative expression analyses indicated that HaDHCR24-1 was highly enriched in the midgut where dietary sterol uptake occurs. Compared to the control, the DHCR24-1 mutant larvae generated by clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR-associated nuclease 9 technology accumulated more desmosterol in the gut, while the content of cholesterol was significantly reduced. A similar phenomenon was observed when the DHCR24 inhibitor, amiodarone, was applied to the insects. Moreover, DHCR24-1 played an important role for the usage of ß-sitosterol, a major sterol in plants, in H. armigera, and loss of function of DHCR24-1 resulted in higher mortality on ß-sitosterol. However, the DHCR24 homolog does not necessarily exist in the genomes of all insects. The loss of this gene occurred more frequently in the insects feeding on animals, which further support the role of DHCR24-1 in using phytosterols. This gene may have important potential in developing new strategies to control herbivory pests in Lepidoptera and other insect orders.

Neuropeptide natalisin regulates reproductive behaviors in Spodoptera frugiperda.

Natalisin (NTL) is a conserved neuropeptide, only present in insects, that has been reported to regulate their sexual activity. In this study, we investigated the involvement of NTL in the reproductive behaviors of a major invasive pest, Spodoptera frugiperda. We identified NTL precursor-encoded transcripts, and evaluated their transcript levels in different stages and tissues of S. frugiperda. The results showed that the NTL transcript level was expressed in both male and female pupae and both male and female adults in the later stage. It was highly expressed in male pupae, 3-day-old male and female adults, and 5-day-old male adults. In different tissues, the expression level is higher in the male and female adult brain and male testis. Immunohistochemical staining of the brain of S. frugiperda female and male adults revealed that three pairs of brain neurons of S. frugiperda adults of both sexes secreted and expressed NTL. To study the role of NTL in reproductive behaviors, NTL was silenced in S. frugiperda male and female adults by RNA interference (RNAi) technology, the results showed that silencing NTL could significantly affect the sexual activity behavior of the adults, reducing the calling rate of females, the courtship rate of males, and the mating rate. In summary, this study emphasizes the important role of NTL in regulating the mating behavior and sexual activity of S. frugiperda in both male and female adults, potentially laying a foundation to employ NTL as a new insect-specific target to control populations of pest insects.

High-temperature responses of Myzus persicae and its parasitoid Aphidius gifuensis in relation to heat level, duration and developmental stage.

BACKGROUND: Understanding how parasitoids respond to temperature is crucial for improving biological control strategies under the context of global warming. This study examined the suitability of Myzus persicae and its parasitoid Aphidius gifuensis to varying temperature conditions, as well as the stage-specific response of A. gifuensis to high temperatures. RESULTS: High temperatures had a significant impact on the both M. persicae and A. gifuensis. When exposed to 36°C, M. persicae developed more slowly and produced smaller adults compared to control, regardless of the duration of exposure (2, 4 or 6 h); additionally, the survival rate of M. persicae nymphs sharply decreased under these conditions. Exposure to 36°C for 4 h negatively impacted the development of A. gifuensis. Female parasitoids exposed to 32°C developed into smaller adults, whereas males exposed to all three temperature levels were smaller compared to control group. Female parasitoids exposed to high temperatures, regardless of the specific heat level and duration, exhibited reduced longevity and decreased fecundity. None of the parasitoids exposed to 36°C for 6 h daily developed into adults. Heat treated during early developmental stages (2 and 4 days old) had a greater influence on parasitoid development, whereas heat treatment at 4 and 6 days old had a more significant impact on its fecundity. CONCLUSION: High temperatures not only directly affected the performance of A. gifuensis, but also exerted indirect effects by influencing the quality of the host aphids M. persicae. The deleterious effects of high temperature on larvae can persist into the adult stage, affecting the longevity and reproduction of adults. These findings are important for the utilization of A. gifuensis in the control of M. persicae in warming environments. © 2024 Society of Chemical Industry.

Odorant-binding protein CrufOBP1 in Cotesia ruficrus females plays a pivotal role in the detection of Spodoptera frugiperda larvae.

Cotesia ruficrus presents a promising local natural enemy for controlling the invasive fall armyworm Spodoptera frugiperda in China. However, the mechanisms underlying how C. ruficrus locates its target pest remain unclear. In this study, we analyzed the expression patterns of 18 CrufOBPs across different developmental stages of C. ruficrus, and found that CrufOBP1 exhibited consistent and high expression levels in female adults. CrufOBP1 transcript was predominantly localized in sensilla placodea and sensilla trichodea on the antennae. Additionally, we confirmed the binding properties of CrufOBP1 protein to various cuticular compounds of S. frugiperda larvae. Subsequent electroantennogram and behavioral assays revealed that 1-(2-hydroxy-5-methylphenyl)-ethanone attracted female C. ruficrus, consequently increased the parasitism rate. However, upon silencing CrufOBP1, females exhibited reduced attraction towards 1-(2-hydroxy-5-methylphenyl)-ethanone, indicating the crucial role of CrufOBP1 in the chemoreception of C. ruficrus. These findings shed light on the kairomone-based mechanism employed by C. ruficrus to locate S. frugiperda larvae and hold a promise for the development of environmentally friendly pest management strategies.

Involvement of Chemosensory Protein CrufCSP3 in Perception of the Host Location in a Parasitic Wasp Cotesia ruficrus.

Chemosensory proteins (CSPs) constitute a class of olfactory proteins localized in insect sensory organs that serve a crucial function in decoding external chemical stimuli. This study aims to elucidate the involvement of CrufCSP3 in olfactory perception within the context of Cotesia ruficrus, an indigenous endoparasitoid targeting the invasive pest Spodoptera frugiperda. Through fluorescence-competitive binding assays and site-directed mutagenesis, we pinpointed four amino acids as pivotal residues involved in the interaction between CrufCSP3 and five host-related compounds. Subsequent RNA interference experiments targeting CrufCSP3 unveiled a reduced sensitivity to specific host-related compounds and a decline in the parasitism rate of the FAW larvae. These findings unequivocally indicate the essential role of CrufCSP3 in the chemoreception process of C. ruficrus. Consequently, our study not only sheds light on the functional importance of CSPs in parasitic wasp behavior but also contributes to the development of eco-friendly and efficacious wasp behavior modifiers for effectively mitigating pest population surges.

Wing Plasticity Is Associated with Growth and Energy Metabolism in Two Color Morphs of the Pea Aphid.

The pea aphid, Acyrthosiphon pisum, is a major pest of legume crops, exhibiting distinct polymorphism in terms of wings and body color. We found that, under crowded conditions, the red morph A. pisum produced more winged offspring than the green morph. The signaling pathways involved in aphid wing determination, like insulin and ecdysone, also play important roles in regulating growth, development, and metabolism. Thus, here, we examined the association between the wing-producing ability and the growth rate, development time, reproductive capacity, and energy metabolism in these two color morphs. The growth rate of red morphs was significantly higher than that of green morphs, whereas green morphs produced more offspring during the first 6 days of the adult stage. Red morphs accumulated higher levels of glycogen and triglycerides and consumed more triglycerides during starvation; however, green aphids consumed more trehalose during food deprivation. Red aphids exhibited stronger starvation tolerance, possibly due to their higher triglyceride catabolic activity. Furthermore, the expression levels of genes involved in the insulin pathway, glycolysis, and lipolysis in red aphids were higher than those in green aphids. These results suggest that the wing-producing ability of the pea aphid may be associated with its growth and metabolism, which may be due to the shared regulatory signaling pathways.

Aspongopus chinensis ach-miR-276a-3p induces breast cancer cell cycle arrest by targeting APPL2 to regulate the CDK2-Rb-E2F1 signaling pathway.

Breast cancer, the most common cancer, presents a significant challenge to the health and longevity of women. Aspongopus chinensis Dallas is an insect with known anti-breast cancer properties. However, the anti-breast cancer effects and underlying mechanisms have not been elucidated. Exogenous microRNAs (miRNAs), which are derived from plants and animals, have been revealed to have notable capacities for controlling the proliferation of cancerous cells. To elucidate the inhibitory effects of miRNAs derived from A. chinensis and the regulatory mechanism involved in the growth of breast cancer cells, miRNA sequencing was initially employed to screen for miRNAs both in A. chinensis hemolymph and decoction and in mouse serum and tumor tissue after decoction gavage. Subsequently, the experiments were performed to assess the suppressive effect of ach-miR-276a-3p, the miRNA screened out from a previous study, on the proliferation of MDA-MB-231 and MDA-MB-468 breast cancer cell lines in vitro and in vivo. Finally, the regulatory mechanism of ach-miR-276a-3p in MDA-MB-231 and MDA-MB-468 breast cancer cells was elucidated. The results demonstrated that ach-miR-276a-3p notably inhibited breast cancer cell proliferation, migration, colony formation, and invasion and induced cell cycle arrest at the G0/G1 phase. Moreover, the ach-miR-276a-3p mimics significantly reduced the tumor volume and weight in xenograft tumor mice. Furthermore, ach-miR-276a-3p could induce cell cycle arrest by targeting APPL2 and regulating the CDK2-Rb-E2F1 signaling pathway. In summary, ach-miR-276a-3p, derived from A. chinensis, has anti-breast cancer activity by targeting APPL2 and regulating the CDK2-Rb-E2F1 signaling pathway and can serve as a promising candidate anticancer agent.

Molecular mechanisms for selective action of afidopyropen to Myzus persicae and Coccinella septempunctata.

BACKGROUND: Afidopyropen is a novel insecticide with high selectivity between sucking insects such as the peach aphids Myzus persicae and natural enemies like the seven-spotted lady beetle Coccinella septempunctata. However, the mechanisms of selective action for afidopyropen remain unknown. RESULTS: The LC50 values of afidopyropen to the 1st-4th instar larvae and adult C. septempunctata were 372- to more than 7267-fold higher than that to adult M. persicae. Though the activity of cytochrome P450s in M. persicae was 6.1- to 7.5-fold higher than that in C. septempunctata, the latter has much higher activities of carboxylesterase (CarEs) and glutathione S-transferases (GSTs), and the crude enzyme of C. septempunctata and M. persicae showed similar metabolism efficiency to afidopyropen. Molecular docking results demonstrated that afdopyropen showed higher binding affinity to the vanilloid-type transient receptor potential (TRPV) channel of M. persicae (-9.1 kcal/mol) than to that of C. septempunctata (-8.2 kcal/mol). And the EC50 value of afdopyropen to the TRPV channel of C. septempunctata (41 360 nM) was 19 885-fold higher than that in M. persicae (2.08 nM). CONCLUSIONS: Our results demonstrated that the significantly different sensitivity of M. persicae and C. septempunctata TRPV channel to afidopyropen play a key role in the high selectivity of afidopyropen. These findings provide new insights into the selective mechanisms of afidopyropen against insect pests and natural enemies as well as the theory support for coordinated application of chemical control and biological control. © 2024 Society of Chemical Industry.

Effects of thiamethoxam on physiological and molecular responses to potato plant (Solanum tuberosum), green peach aphid (Myzus persicae), and parasitoid (Aphidius gifuensis).

BACKGROUND: To improve integrated pest management (IPM) performance it is essential to assess pesticide side effects on host plants, insect pests, and natural enemies. The green peach aphid (Myzus persicae Sulzer) is a major insect pest that attacks various crops. Aphidius gifuensis is an essential natural enemy of M. persicae that has been applied effectively in controlling M. persicae. Thiamethoxam is a neonicotinoid pesticide widely used against insect pests. RESULTS: The current study showed the effect of thiamethoxam against Solanum tuberosum, M. persicae, and A. gefiuensis and the physiological and molecular response of the plants, aphids, and parasitoids after thiamethoxam application. Thiamethoxam affected the physical parameters of S. tuberosum and generated a variety of sublethal effects on M. persicae and A. gefiuensis, including nymph development time, adult longevity, and fertility. Our results showed that different thiamethoxam concentrations [0.1, 0.5, and 0.9 µm active ingredient (a.i.)/L] on different time durations (2, 6, and 10 days) increased the antioxidant enzyme activities SOD, POD, and CAT of S. tuberosum, M. persicae, and A. gefiuensis significantly compared with the control. Our results also showed that different thiamethoxam concentrations (0.1, 0.5, and 0.9 µm a.i./L) on different time durations (2, 6, and 10 days) increased the expression of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione-S-transferase (GST) genes of S. tuberosum, M. persicae, and A. gefiuensis compared with the control. CONCLUSION: Our findings reveal that using thiamethoxam at suitable concentrations and time durations for host plants and natural enemies may enhance natural control through the conservation of natural enemies by overcoming any fitness disadvantages. © 2024 Society of Chemical Industry.

Identification of amino acid residues that are crucial for afidopyropen binding to the TRPV channel of Myzus persicae (Sulzer).

Afidopyropen is highly effective against sucking insects, including the Myzus persicae, that modulates the transient receptor potential vanilloid (TRPV) channel. However, the action mechanisms of afidopyropen to the TRPV channel remain unknown. In this study, the genes encoding the Nanchung (MpNan) and Inactive (MpIav) subunits of the TRPV channel of M. persicae (MpTRPV) were cloned, and their spatiotemporal expression profiles were investigated. Then, MpTRPV was functionally expressed in Xenopus laevis oocytes, and the AA residues crucial for afidopyropen binding were identified using the two-electrode voltage clamp (TEVC) technique. The results showed that both MpNan and MpIav exhibited the highest expression in the antennae and were most abundant in the 4th instar nymphs and adults. Knockdown of these two genes by RNAi greatly increased the toxicity of afidopyropen to the aphids. Moreover, the AA residues involved in afidopyropen binding to MpNan were predicted and L412 was further identified as the key residue for binding by TEVC analysis. The results also showed that afdopyropen and pymetrozine share the same binding site. These findings lay a foundation not only for exploring the mechanisms of pest target resistance to afidopyropen and pymetrozine but also for developing new insecticides targeting the TRPV channels of pests.

Optimal cold storage protocol for Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), a biological control agent for coleopteran pests in stored products.

BACKGROUND: Anisopteromalus calandrae (Howard) is a solitary ectoparasitoid with wide-ranging potential applications as a natural biological control agent against various coleopterous pests in food warehouses. Implementing an effective cold storage program is crucial for extending the shelf life of biological control agents and ensuring their stable and abundant supply. Herein, we attempted to determine the optimal cold storage conditions for Anisopteromalus calandrae by investigating the effect of cold storage at three different temperatures (7, 13, and 19 °C) for 7, 21, and 35 days on four developmental stages (late-instar larvae, early-stage pupae, mid-stage pupae, and 2-day-old adults). Additionally, we explored the maximum cold storage potential by observing early-stage pupae stored at 13 °C for various durations (30, 60, 90, 120, and 150 days). RESULTS: The most suitable cold storage temperature for the early-stage pupae of Anisopteromalus calandrae was 13 °C, and the highest adult emergence rate (98.3%) was after 90 days of storage at 13 °C. Furthermore, we did not find any significant effect on longevity (female: 44.3 days; male: 38.1 days) or fecundity (121.7 wasps). The female ratio ranged from 43.5% to 50.8%. More importantly, cold storage did not adversely affect the developmental duration or fecundity of the offspring. CONCLUSION: This study offers crucial insights for managing Anisopteromalus calandrae populations under laboratory conditions and lays the foundation for potential industrial production and development. © 2023 Society of Chemical Industry.

Acetyl coenzyme A carboxylase modulates lipogenesis and sugar homeostasis in Blattella germanica.

Lipid and sugar homeostasis is critical for insect development and survival. In this study, we characterized an acetyl coenzyme A carboxylase gene in Blattella germanica (BgACC) that is involved in both lipogenesis and sugar homeostasis. We found that BgACC was dominantly expressed in the fat body and integument, and was significantly upregulated after molting. Knockdown of BgACC in 5th-instar nymphs did not affect their normal molting to the next nymphal stage, but it caused a lethal phenotype during adult emergence. BgACC-RNA interference (RNAi) significantly downregulated total free fatty acid (FFA) and triacylglycerol (TAG) levels, and also caused a significant decrease of cuticular hydrocarbons (CHCs). Repression of BgACC in adult females affected the development of oocytes and resulted in sterile females, but BgACC-RNAi did not affect the reproductive ability of males. Interestingly, knockdown of BgACC also changed the expression of insulin-like peptide genes (BgILPs), which mimicked a physiological state of high sugar uptake. In addition, BgACC was upregulated when B. germanica were fed on a high sucrose diet, and repression of BgACC upregulated the expression of the glycogen synthase gene (BgGlyS). Moreover, BgACC-RNAi increased the circulating sugar levels and glycogen storage, and a longevity assay suggested that BgACC was important for the survival of B. germanica under conditions of high sucrose uptake. Our results confirm that BgACC is involved in multiple lipid biogenesis and sugar homeostasis processes, which further modulates insect reproduction and sugar tolerance. This study benefits our understanding of the crosstalk between lipid and sugar metabolism.

Systemic resistance induced in tomato plants by Beauveria bassiana-derived proteins against tomato yellow leaf curl virus and aphid Myzus persicae.

BACKGROUND: Tomato (Solanum lycopersicum L.) is an economically important vegetable crop around the globe. Tomato yellow leaf curling (TYLC) is the most devastating viral disease posing a serious threat to tomato production throughout the tropical and subtropical world. Induction of microbe-mediated systemic resistance in plants has been of great interest in recent years as a novel microbiological tool in disease and insect pest management. This in-vitro study aimed to determine the effectiveness of different strains (BB252, BB72 and ARSEF-2860) of a hypocreal fungus Beauveria bassiana against TYLCV disease and aphid Myzus persicae. Potted tomato plants exogenously treated with conidial and filtrate suspensions of B. bassiana strains and of their partially purified or purified proteins were exposed to TYLCV inoculum and aphid M. persicae. RESULTS: Results showed a significant suppression of TYLCV disease severity index by the exogenous application of conidial, filtrate and protein treatments of all B. bassiana strains and this response was directly proportional to the treatment concentration. Similarly, mean fecundity rate of M. persicae was also significantly reduced by the highest concentration of ARSEF-2860-derived elicitor protein PeBb1, followed by the highest concentrations of BB252- and BB72-derived partially purified proteins. Moreover, these B. bassiana-derived proteins also caused a significant upregulation of most of the plant immune marker genes associated with plant defense. CONCLUSION: Overall, the study findings suggest that these B. bassiana strains and their partially purified or purified elicitor proteins could be effective biological tools for the management of TYLCV and aphid infestation on tomato plants. © 2023 Society of Chemical Industry.

Effects of repeated afidopyropen treatment on the structure and function of the soil microbial community.

Chemical insecticides are the most effective pest control agents. Afidopyropen is a novel insecticide used against sap-sucking insects, such as aphids. However, the effects of repeated afidopyropen application on the structure and function of soil microorganisms remain unknown. In this study, the changes in the enzyme activities, community structure and function, and relative abundance of antibiotic resistance ontology (ARO) of soil microorganisms were investigated during three repeated afidopyropen applications under laboratory conditions at the maximum recommended dosage (M1) and 10 times the M1 (M10). The neutral phosphatase (NPA) and catalase (CAT) activities in the soil were significantly suppressed after afidopyropen treatment. The Simpson diversity index (1/D) and Shannon-Wiener diversity index (H) also decreased in both the M1 and M10 afidopyropen-treated soils, indicating a remarkable decrease in soil microorganism diversity. The average well color development (AWCD) first increased and subsequently recovered to normal levels after the third application of the insecticide, suggesting that afidopyropen application could increase the metabolic activity of soil microorganisms. Metagenomic analysis showed that repeated afidopyropen application in both the M1 and M10 treatment groups altered the community structure of soil microorganisms, albeit in different ways. Furthermore, repeated afidopyropen application significantly increased the relative ARO abundance, especially in the M10 treatment, with the most dominant AROs being adeF, baeS, and IND-6. These findings reveal the effects of excessive afidopyropen application on soil microorganisms and lay an important foundation for the comprehensive evaluation of the impact of this insecticide on the environment.

Plants affect the horizontal transmission of a new densovirus infecting the green peach aphid Myzus persicae by modulating honeydew production.

In a tritrophic context of plant-insect-entomopathogen, plants play important roles in modulating the interaction of insects and their pathogenic viruses. Currently, the influence of plants on the transmission of insect viruses has been mainly studied on baculoviruses and some RNA viruses, whereas the impact of plants on other insect viruses is largely unknown. Here, we identified a new densovirus infecting the green peach aphid Myzus persicae and tested whether and how host plants influence the transmission of the aphid densovirus. The complete single-stranded DNA genome of the virus, M. persicae densovirus 2, is 5 727 nt and contains inverted terminal repeats. Transcription and phylogenetic analysis indicated that the virus was distinct from other a few identified aphid densoviruses. The virus abundance was detected highly in the intestinal tract of aphids, compared with the lower level of it in other tissues including head, embryo, and epidermis. Cabbage and pepper plants had no obvious effect on the vertical transmission and saliva-mediated horizontal transmission of the virus. However, the honeydew-mediated horizontal transmission among aphids highly depended on host plants (65% on cabbages versus 17% on peppers). Although the virus concentration in the honeydew produced by aphids between 2 plants was similar, the honeydew production of the infected aphids reared on peppers was dramatically reduced. Taken together, our results provide evidence that plants influence the horizontal transmission of a new densovirus in an aphid population by modulating honeydew secretion of aphids, suggesting plants may manipulate the spread of an aphid-pathogenic densovirus in nature.