A salivary gland-secreted peptide regulates insect systemic growth

Knockout of silk fibroin genes in Plutella xylostella results in decreased fitness and performance

BACKGROUND

The ability of insects to spin silk is crucial for their survival, reproduction, and interactions with the environment. The diamondback moth (DBM), Plutella xylostella, a serious agricultural pest, relies on silk production, which influences its behavior and population dynamics.

RESULTS

This study employed CRISPR/Cas9 technology to knock out three genes, that is, silk fibroin heavy chain (PxFibH), silk fibroin light chain (PxFibL), and fibrohexamerin (PxP25), to investigate their roles in silk gland development and related biological traits. We successfully generated PxFibH, PxFibL, and PxP25 knockout mutants, which displayed defective cocoon formation and developed into naked pupae. Further analysis revealed significant alterations in silk gland structure and various biological parameters, including increased larval mortality, prolonged developmental time, reduced pupal weight, and shortened adult lifespan.

CONCLUSIONS

These findings highlight the importance of silk fibroin genes in silk production and growth development in P. xylostella, positioning them as potential targets for innovative pest control strategies. © 2025 Society of Chemical Industry.

Proliferation dynamic of Paranosema locustae after infection and histopathogenic features on Locusta migratoria

Paranosema locustae are specialized parasites of Orthoptera that have been applied widely in the control of grasshoppers in many parts of the world. However, it is slow to kill insects, and how it works in the host is unclear. This work aimed to examine the proliferation of P. locustae within locust tissues and characterize the histological alterations occurring in the midgut, hindgut, and gonads of infected Locusta migratoria. The results showed that during the later stage of infection, the reproduction of P. locustae was most prominent in the fat body and salivary glands (109.26 and 108.91 copies /ug DNA, respectively). In contrast, the load of P. locustae was least in the craw and midgut (107.37 and 107.58 copies /ug DNA, respectively), illustrating that the proliferation of P. locustae in the body of locusts had a tissue tendency. The histopathological study revealed that lesions in the hindgut occurred prior to those in the midgut, indicating that P. locustae may have a mechanism for survival that enables it to avoid immune responses in specific organs. The testis exhibited earlier lesions compared to the ovaries, and in the advanced stages of infection, the testis harbored a higher load of P. locustae than the ovaries, suggesting a more pronounced impact on the male reproductive organs in comparison to the female ones. The results of our study enhance our comprehension of the rapid growth and disease-causing mechanism of P. locustae, which can serve as a basis for enhancing its ability to kill insects. © 2024 Society of Chemical Industry.

USP8 and Hsp70 regulate endoreplication by synergistically promoting Fzr deubiquitination and stabilization

Endoreplication is characterized by multiple rounds of DNA replication without cell division and determines the growth and final size of endoreplicating cells and tissues in eukaryotes. The cyclic ubiquitination and degradation of several cell cycle regulators are required for endoreplication progression. However, the deubiquitinase that deubiquitinates and stabilizes key factors to modulate endoreplication remains unknown. Here, we found in the endoreplicating Drosophila salivary gland and Bombyx silk gland that the depletion of ubiquitin-specific peptidase 8 (USP8) led to endoreplication arrest and a decrease in gland size. Mechanistically, we showed that USP8 interacted with the Fizzy-related (Fzr) protein, a conserved master regulator of endoreplication, thereby deubiquitinating and stabilizing Fzr to modulate endoreplication. Moreover, the molecular chaperone heat shock protein 70 (Hsp70) mediated proper folding of Fzr and increased the interaction between Fzr and USP8, thereby promoting the deubiquitination and stabilization of Fzr. Together, our study demonstrates that USP8 and Hsp70 regulate endoreplication by synergistically maintaining Fzr stability though deubiquitination.

Insight into Rice Resistance to the Brown Planthopper: Gene Cloning, Functional Analysis, and Breeding Applications

This review provides a comprehensive overview of the current understanding of rice resistance to the brown planthopper (BPH), a major pest that poses significant threats to rice production through direct feeding damage and by transmitting viruses such as Rice grassy stunt virus (RGSV) and Rice ragged stunt virus (RRSV). We highlight the emergence of various BPH biotypes that have overcome specific resistance genes in rice. Advances in genetic mapping and cloning have identified 17 BPH resistance genes, classified into typical R genes encoding nucleotide-binding leucine-rich repeat (NLR) proteins and atypical R genes such as lectin receptor kinases and proteins affecting cell wall composition. The molecular mechanisms of these genes involve the activation of plant defense pathways mediated by phytohormones like jasmonic acid (JA), salicylic acid (SA), and ethylene, as well as the production of defensive metabolites. We also examine the complex interactions between BPH salivary proteins and rice defense responses, noting how salivary effectors can both suppress and trigger plant immunity. The development and improvement of BPH-resistant rice varieties through conventional breeding and molecular marker-assisted selection are discussed, including strategies like gene pyramiding to enhance resistance durability. Finally, we outline the challenges and future directions in breeding for durable BPH resistance, emphasizing the need for continued research on resistance mechanisms and the development of rice varieties with broad-spectrum and long-lasting resistance.

The exocyst complex controls multiple events in the pathway of regulated exocytosis

Eukaryotic cells depend on exocytosis to direct intracellularly synthesized material toward the extracellular space or the plasma membrane, so exocytosis constitutes a basic function for cellular homeostasis and communication between cells. The secretory pathway includes biogenesis of secretory granules (SGs), their maturation and fusion with the plasma membrane (exocytosis), resulting in release of SG content to the extracellular space. The larval salivary gland of Drosophila melanogaster is an excellent model for studying exocytosis. This gland synthesizes mucins that are packaged in SGs that sprout from the trans-Golgi network and then undergo a maturation process that involves homotypic fusion, condensation, and acidification. Finally, mature SGs are directed to the apical domain of the plasma membrane with which they fuse, releasing their content into the gland lumen. The exocyst is a hetero-octameric complex that participates in tethering of vesicles to the plasma membrane during constitutive exocytosis. By precise temperature-dependent gradual activation of the Gal4-UAS expression system, we have induced different levels of silencing of exocyst complex subunits, and identified three temporarily distinctive steps of the regulated exocytic pathway where the exocyst is critically required: SG biogenesis, SG maturation, and SG exocytosis. Our results shed light on previously unidentified functions of the exocyst along the exocytic pathway. We propose that the exocyst acts as a general tethering factor in various steps of this cellular process.

Depletion of lipid storage droplet-1 delays endoreplication progression and induces cell death in Drosophila salivary gland

Perilipins are evolutionarily conserved from insects to mammals. Drosophila lipid storage droplet-1 (LSD-1) is a lipid storage droplet membrane surface-binding protein family member and a counterpart to mammalian perilipin 1 and is known to play a role in lipolysis. However, the function of LSD-1 during specific tissue development remains under investigation. This study demonstrated the role of LSD-1 in salivary gland development. Knockdown of Lsd-1 in the salivary gland was established using the GAL4/UAS system. The third-instar larvae of knockdown flies had small salivary glands containing cells with smaller nuclei. The null mutant Drosophila also showed the same phenotype. The depletion of LSD-1 expression induced a delay of endoreplication due to decreasing CycE expression and increasing DNA damage. Lsd-1 genetically interacted with Myc in the third-instar larvae. These results demonstrate that LSD-1 is involved in cell cycle and cell death programs in the salivary gland, providing novel insight into the effects of LSD-1 in regulating salivary gland development and the interaction between LSD-1 and Myc.

Roles of herbivorous insects salivary proteins

The intricate relationship between herbivorous insects and plants has evolved over millions of years, central to this dynamic interaction are salivary proteins (SPs), which mediate key processes ranging from nutrient acquisition to plant defense manipulation. SPs, sourced from salivary glands, intestinal regurgitation or acquired through horizontal gene transfer, exhibit remarkable functional versatility, influencing insect development, behavior, and adhesion mechanisms. Moreover, SPs play pivotal roles in modulating plant defenses, to induce or inhibit plant defenses as elicitors or effectors. In this review, we delve into the multifaceted roles of SPs in herbivorous insects, highlighting their diverse impacts on insect physiology and plant responses. Through a comprehensive exploration of SP functions, this review aims to deepen our understanding of plant-insect interactions and foster advancements in both fundamental research and practical applications in plant-insect interactions.

Unveiling the Slippery Secrets of Saliva: Effector Proteins of Phloem-Feeding Insects

Phloem-feeding insects include many important agricultural pests that cause crop damage globally, either through feeding-related damage or upon transmission of viruses and microbes that cause plant diseases. With genetic crop resistances being limited to most of these pests, control relies on insecticides, which are costly and damaging to the environment and to which insects can develop resistance. Like other plant parasites, phloem-feeding insects deliver effectors inside their host plants to promote susceptibility, most likely by a combination of suppressing immunity and promoting nutrient availability. The recent emergence of the effector paradigm in plant-insect interactions is highlighted by increasing availability of effector repertoires for a range of species and a broadening of our knowledge concerning effector functions. Here, we focus on recent progress made toward identification of effector repertoires from phloem-feeding insects and developments in effector biology that will advance functional characterization studies. Importantly, identification of effector activities from herbivorous insects promises to provide new avenues toward development of crop protection strategies. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Identification of neuropeptides and their G protein-coupled receptors in the predatory stink bug, Arma custos (Hemiptera: Pentatomidae)

The predatory stink bug Arma custos has been selected as an effective biological control agent and has been successfully massly bred and released into fields for the control of a diverse insect pests. As a zoophytophagous generalist, A. custos relies on a complex neuropeptide signaling system to prey on distinct food and adapt to different environments. However, information about neuropeptide signaling genes in A. custos has not been reported to date. In the present study, a total of 57 neuropeptide precursor transcripts and 41 potential neuropeptide G protein-coupled receptor (GPCR) transcripts were found mainly using our sequenced transcriptome data. Furthermore, a number of neuropeptides and their GPCR receptors that were enriched in guts and salivary glands of A. custos were identified, which might play critical roles in feeding and digestion. Our study provides basic information for an in-depth understanding of biological and ecological characteristics of the predatory bug and would aid in the development of better pest management strategies based on the effective utilization and protection of beneficial natural enemies.

Transcriptome analysis reveals salivary gland-specific neuropeptide signaling genes in the predatory stink bug, Picromerus lewisi

Predatory stink bugs derive from phytophagous stink bugs and evolved enhanced predation skills. Neuropeptides are a diverse class of ancient signaling molecules that regulate physiological processes and behavior in animals, including stink bugs. Neuropeptide evolution might be important for the development of predation because neuropeptides can be converted to venoms that impact prey. However, information on neuropeptide signaling genes in predatory stink bugs is lacking. In the present study, neuropeptide signaling genes of Picromerus lewisi, an important predatory stink bug and an effective biological agent, were comprehensively identified by transcriptome analysis, with a total of 59 neuropeptide precursor genes and 58 potential neuropeptide receptor genes found. In addition, several neuropeptides and their receptors enriched in salivary glands of P. lewisi were identified. The present study and subsequent functional research contribute to an in-depth understanding of the biology and behavior of the predatory bugs and can provide basic information for the development of better pest management strategies, possibly including neuropeptide receptors as insecticide targets and salivary gland derived venom toxins as novel killing moleculars.

Wds-Mediated H3K4me3 Modification Regulates Lipid Synthesis and Transport in Drosophila

Lipid homeostasis is essential for insect growth and development. The complex of proteins associated with Set 1 (COMPASS)-catalyzed Histone 3 lysine 4 trimethylation (H3K4me3) epigenetically activates gene transcription and is involved in various biological processes, but the role and molecular mechanism of H3K4me3 modification in lipid homeostasis remains largely unknown. In the present study, we showed in Drosophila that fat body-specific knockdown of will die slowly (Wds) as one of the COMPASS complex components caused a decrease in lipid droplet (LD) size and triglyceride (TG) levels. Mechanistically, Wds-mediated H3K4me3 modification in the fat body targeted several lipogenic genes involved in lipid synthesis and the Lpp gene associated with lipid transport to promote their expressions; the transcription factor heat shock factor (Hsf) could interact with Wds to modulate H3K4me3 modification within the promoters of these targets; and fat body-specific knockdown of Hsf phenocopied the effects of Wds knockdown on lipid homeostasis in the fat body. Moreover, fat body-specific knockdown of Wds or Hsf reduced high-fat diet (HFD)-induced oversized LDs and high TG levels. Altogether, our study reveals that Wds-mediated H3K4me3 modification is required for lipid homeostasis during Drosophila development and provides novel insights into the epigenetic regulation of insect lipid metabolism.

Mammalian puberty: a fly perspective

Mammalian puberty and Drosophila metamorphosis, despite their evolutionary distance, exhibit similar design principles and conservation of molecular components. In this Viewpoint, we review recent advances in this area and the similarities between both processes in terms of the signaling pathways and neuroendocrine circuits involved. We argue that the detection and uptake of peripheral fat by Drosophila prothoracic endocrine cells induces endomembrane remodeling and ribosomal maturation, leading to the acquisition of high biosynthetic and secretory capacity. The absence of this fat-neuroendocrine interorgan communication leads to giant, obese, non-pupating larvae. Importantly, human leptin is capable of signaling the pupariation process in Drosophila, and its expression prevents obesity and triggers maturation in mutants that do not pupate. This implies that insect metamorphosis can be used to address issues related to the biology of leptin and puberty.