Molecular Identification and Immunity Functional Characterization of Lmserpin1 in Locusta migratoria manilensis

Warmer temperatures trigger insecticide-associated pest outbreaks

BACKGROUND

Rising global temperatures are associated with emerging insect pests, reflecting earlier and longer insect activity, faster development, more generations per year and changing species' ranges. Insecticides are often the first tools available to manage these new threats. In the southeastern US, sweet potato whitefly (Bemisia tabaci) has recently become the major threat to vegetable production. We used data from a multi-year, regional whitefly monitoring network to search for climate, land use, and management correlates of whitefly activity.

RESULTS

Strikingly, whiteflies were detected earlier and grew more abundant in landscapes with greater insecticide use, but only when temperatures were also relatively warm. Whitefly outbreaks in hotter conditions were not associated with specific active ingredients used to suppress whiteflies, which would be consistent with a regional disruption of biocontrol following sprays for other pests. In addition, peak whitefly detections occurred earlier in areas with more vegetable production, but later with more cotton production, consistent with whiteflies moving among crops.

CONCLUSION

Altogether, our findings suggest possible links between warmer temperatures, more abundant pests, and frequent insecticide applications disrupting biological control, though this remains to be explicitly demonstrated. Climate-initiated pesticide treadmills of this type may become an increasingly common driver of emerging pest outbreaks as global change accelerates. © 2023 Society of Chemical Industry.

MicroRNA Targets PAP1 to Mediate Melanization in Plutella xylostella (Linnaeus) Infected by Metarhizium anisopliae

MicroRNAs (miRNAs) play a pivotal role in important biological processes by regulating post-transcriptional gene expression and exhibit differential expression patterns during development, immune responses, and stress challenges. The diamondback moth causes significant economic damage to crops worldwide. Despite substantial advancements in understanding the molecular biology of this pest, our knowledge regarding the role of miRNAs in regulating key immunity-related genes remains limited. In this study, we leveraged whole transcriptome resequencing data from Plutella xylostella infected with Metarhizium anisopliae to identify specific miRNAs targeting the prophenoloxidase-activating protease1 (PAP1) gene and regulate phenoloxidase (PO) cascade during melanization. Seven miRNAs (pxy-miR-375-5p, pxy-miR-4448-3p, pxy-miR-279a-3p, pxy-miR-3286-3p, pxy-miR-965-5p, pxy-miR-8799-3p, and pxy-miR-14b-5p) were screened. Luciferase reporter assays confirmed that pxy-miR-279a-3p binds to the open reading frame (ORF) and pxy-miR-965-5p to the 3' untranslated region (3' UTR) of PAP1. Our experiments demonstrated that a pxy-miR-965-5p mimic significantly reduced PAP1 expression in P. xylostella larvae, suppressed PO activity, and increased larval mortality rate. Conversely, the injection of pxy-miR-965-5p inhibitor could increase PAP1 expression and PO activity while decreasing larval mortality rate. Furthermore, we identified four LncRNAs (MSTRG.32910.1, MSTRG.7100.1, MSTRG.6802.1, and MSTRG.22113.1) that potentially interact with pxy-miR-965-5p. Interference assays using antisense oligonucleotides (ASOs) revealed that silencing MSTRG.7100.1 and MSTRG.22113.1 increased the expression of pxy-miR-965-5p. These findings shed light on the potential role of pxy-miR-965-5p in the immune response of P. xylostella to M. anisopliae infection and provide a theoretical basis for biological control strategies targeting the immune system of this pest.

Identification and functional analysis of serine protease inhibitor gene family of Eocanthecona furcellata (Wolff)

The predatory natural enemy Eocanthecona furcellata plays a crucial role in agricultural ecosystems due to its effective pest control measures and defensive venom. Predator venom contains serine protease inhibitors (SPIs), which are the primary regulators of serine protease activity and play key roles in digestion, development, innate immunity, and other physiological regulatory processes. However, the regulation mechanism of SPIs in the salivary glands of predatory natural enemies is still unknown. In this study, we sequenced the transcriptome of E. furcellata salivary gland and identified 38 SPIs genes named EfSPI1∼EfSPI38. Through gene structure, multiple sequence alignment and phylogenetic tree analysis, real-time quantitative PCR (RT-PCR) expression profiles of different developmental stages and different tissues were analyzed. RNAi technology was used to explore the gene function of EFSPI20. The results showed that these 38 EfSPIs genes contained 8 SPI domains, which were serpin, TIL, Kunitz, Kazal, Antistasin, Pacifastin, WAP and A2M. The expression profile results showed that the expression of different types of EfSPIs genes was different at different developmental stages and different tissues. Most of the EfSPIs genes were highly expressed in the egg stage. The EfSPI20, EfSPI21, EfSPI22, and EfSPI24 genes of the Pacifastin subfamily and the EfSPI35 gene of the A2M subfamily were highly expressed in the nymphal and adult stages, which was consistent with the RT-qPCR verification results. These five genes are positively correlated with each other and have a synergistic effect on E. furcellata, and they were highly expressed in salivary glands. After interfering with the expression of the EfSPI20 gene, the survival rate and predatory amount of male and female adults were significantly decreased. Taken together, we speculated some EfSPIs may inhibit trypsin, chymotrypsin, and elastase, and some EfSPIs may be involved in autoimmune responses. EfSPI20 was essential for the predation and digestion of E. furcellata, and the functions of other EfSPIs were discussed. Our findings provide valuable insights into the diversity of EfSPIs in E. furcellata and the potential functions of regulating their predation, digestion and innate immunity, which may be of great significance for developing new pest control strategies.

LmFKBP24 interacts with LmEaster to inhibit the antifungal immunity of Locusta migratoria

Locusta migratoria is one of the most destructive pests that threaten crop growth and food production security in China. Metarhizium anisopliae has been widely used to control locusts around the world. Previous laboratory studies have revealed that LmFKBP24 is significantly upregulated after M. anisopliae infection, suggesting that it may play a role in immune regulation, yet the mechanism remains largely unknown. To gain further insight, we conducted an RNA interference (RNAi) study to investigate the function of LmFKBP24 in the regulation of antifungal immunity and analyzed the expression patterns of immune-induced genes. Our research revealed that LmFKBP24 is activated and upregulated when locusts are infected by M. anisopliae, and it inhibits the expression of antimicrobial peptide (AMP) defensin in the downstream of Toll pathway by combining with LmEaster rather than LmCyPA, thus exerting an immunosuppressive effect. To further investigate this, we conducted yeast two-hybrid (Y2H) and pull down assays to identify the proteins interacting with LmFKBP24. Our results provided compelling evidence for revealing the immune mechanism of L. migratoria and uncovered an innovative target for the development of new biological pesticides. Furthermore, our research indicates that LmFKBP24 interacts with LmEaster through its intact structure, providing a strong foundation for further exploration.

Identification, characterization and spatiotemporal expression analysis of the FKBP family genes in Locusta migratoria

FK506 binding proteins (FKBPs) are a highly-conserved group of proteins known to bind to FK506, an immunosuppressive drug. They play different physiological roles, including transcription regulation, protein folding, signal transduction and immunosuppression. A number of FKBP genes have been identified in eukaryotes; however, very little information about these genes has been reported in Locusta migratoria. Here, we identified and characterized 10 FKBP genes from L. migratoria. Phylogenetic analysis and comparison of domain architectures indicated that the LmFKBP family can be divided into two subfamilies and five subclasses. Developmental and tissue expression pattern analysis revealed that all LmFKBPs transcripts, including LmFKBP46, LmFKBP12, LmFKBP47, LmFKBP79, LmFKBP16, LmFKBP24, LmFKBP44b, LmFKBP53, were periodically expressed during different developmental stages and mainly expressed in the fat body, hemolymph, testis, and ovary. In brief, our work depicts a outline but panoramic picture of LmFKBP family in L. migratoria, and provides a solid foundation to further investigate the molecular functions of LmFKBPs.

Transcriptome Analysis Reveals Early Hemocyte Responses upon In Vivo Stimulation with LPS in the Stick Insect Bacillus rossius (Rossi, 1788)

Simple Summary

Non-model insect species such as B. rossius suffer from a profound gap of knowledge regarding the temporal progression of physiological responses following the challenge with bacterial pathogens or cell wall components thereof. The reason for this mostly lies in the lack of genomic/transcriptomic resources, which would provide an unparalleled in-depth capacity in the analysis of molecular, biochemical, and metabolic mechanisms. We present a high-quality transcriptome obtained from high-coverage sequencing of hemocytes harvested from adult stick insect specimens both pre- and post-LPS stimulation. Such a resource served as the basis for a stringent differential gene expression and functional enrichment analyses, the results of which were characterized and discussed in depth. Selected transcripts encoding for C-type lectins and ML-domain containing proteins were further investigated from a phylogenetic perspective. Overall, these findings shed light on the physiological responses driven by a short-term LPS stimulation in the European stick insect.

Abstract

Despite a growing number of non-model insect species is being investigated in recent years, a greater understanding of their physiology is prevented by the lack of genomic resources. This is the case of the common European stick insect Bacillus rossius (Rossi, 1788): in this species, some knowledge is available on hemocyte-related defenses, but little is known about the physiological changes occurring in response to natural or experimental challenges. Here, the transcriptional signatures of adult B. rossius hemocytes were investigated after a short-term (2 h) LPS stimulation in vivo: a total of 2191 differentially expressed genes, mostly involved in proteolysis and carbohydrate and lipid metabolic processes, were identified in the de novo assembled transcriptome and in-depth discussed. Overall, the significant modulation of immune signals—such as C-type lectins, ML domain-containing proteins, serpins, as well as Toll signaling-related molecules—provide novel information on the early progression of LPS-induced responses in B. rossius.

Host–Pathogen Interactions between Metarhizium spp. and Locusts

The progress in research on the interactions between Metarhizium spp. and locusts has improved our understanding of the interactions between fungal infection and host immunity. A general network of immune responses has been constructed, and the pathways regulating fungal pathogenicity have also been explored in depth. However, there have been no systematic surveys of interaction between Metarhizium spp. and locusts. The pathogenesis of Metarhizium comprises conidial attachment, germination, appressorial formation, and colonization in the body cavity of the host locusts. Meanwhile, the locust resists fungal infection through humoral and cellular immunity. Here, we summarize the crucial pathways that regulate the pathogenesis of Metarhizium and host immune defense. Conidial hydrophobicity is mainly affected by the contents of hydrophobins and chitin. Appressorial formation is regulated by the pathways of MAPKs, cAMP/PKA, and Ca²⁺/calmodulin. Lipid droplets degradation and secreted enzymes contributed to fungal penetration. The humoral response of locust is coordinated by the Toll pathway and the ecdysone. The regulatory mechanism of hemocyte differentiation and migration is elusive. In addition, behavioral fever and density-dependent population immunity have an impact on the resistance of hosts against fungal infection. This review depicts a prospect to help us understand host–pathogen interactions and provides a foundation for the engineering of entomopathogenic fungi and the discovery of insecticidal targets to control insect pests.

Novel proteinase inhibitor from the hemolymph of soybean pest Anticarsia gemmatalis (lepidóptera: Noctuidae): Structural modeling and enzymatic kinetic

New approaches are needed to reduce risks to the environment and natural enemies and to avoid or delay the onset of insecticide resistance. The use of insecticides based on proteinase inhibitors of hemolymph is an alternative for the control of Lepidoptera pests primarily by having low toxicity and short persistence in the environment. Thus, in this study, we describe the purification process and identification of protease inhibitors from hemolymph Anticarsia gemmatalis and their activities against trypsin enzymes. Furthermore, the three-dimensional (3D) structure of the inhibitor and binding mode to trypsin enzymes was determined, and the stability of the inhibitory activity in several pHs and temperature values was evaluated. The inhibitor was characterized as a serpin family inhibitor and named A. gemmatalis hemolymph serpin inhibitor (AHSI), with an approximate mass of 38 ± 2 kDa, highly stable to temperature and pH variations, and with inhibitory capacity on bovine trypsin and gut trypsin of A. gemmatalis demonstrated by calculated Ki values and affinity energy through molecular docking, being a reversible competitive inhibitor that binds to the active site of trypsin-like enzymes. We conclude that the AHSI inhibitor identified from the hemolymph of the soybean pest A. gemmatalis preserves the original structure of the serpin family with a good overall stereochemical quality confirmed from molecular modeling. The docking analysis showed that the reactive site of the inhibitor is in contact with the catalytic cavity of the trypsin with high-affinity energy.