Targeting coat protein II complex genes via RNA interference inhibits female adult feeding and reproductive development in the cabbage beetle Colaphellus bowringi

The PBAP chromatin remodeling complex mediates summer diapause via H3K4me3-driven juvenile hormone regulation in Colaphellus bowringi

Diapause, a developmental arrest mechanism, helps animals to survive seasonal changes via endocrine regulation. While obligate diapause is genetically programmed, facultative diapause is typically triggered by environmental cues such as photoperiod. In insects, this often leads to reproductive diapause characterized by reduced juvenile hormone (JH) signaling, resulting in ovarian arrest and lipid accumulation. However, the molecular link between photoperiod and hormonal control remains poorly understood. In this study, we investigated the cabbage beetle Colaphellus bowringi as our model system. This species exhibits a photoperiodic response, where short-day (SD) conditions promote reproduction, whereas long-day (LD) conditions induce diapause. Our research identified the PBAP chromatin remodeling complex as a key regulator of LD-induced summer diapause entry. Through RNAi screening of 56 transcriptional regulators that were differentially expressed between SD and LD females, we identified BAP170, a PBAP-specific component, as a key mediator of diapause. Knockdown of bap170 in SD females induced reproductive diapause traits, which were reversed by treatment with methoprene, a JH analog, suggesting that the PBAP complex regulates diapause by influencing JH production. We further demonstrated that the PBAP complex modulates JH biosynthesis via SET1/COMPASS-mediated trimethylation of H3K4. Transcriptome analysis and a second RNAi screen identified calmodulin, a calcium-binding messenger protein gene, as a direct target of PBAP-SET1/COMPASS-H3K4me3 signaling in the corpora allata (CA), the primary source of JH. These findings reveal how the chromatin remodeling machinery translates photoperiod signals into endocrine responses governing seasonal adaptation.

Coat protein I genes are essential for the morphogenesis of the intestinal tract in Locusta migratoria

The coat protein I (COPI) complex is crucial in several significant physiological processes in eukaryotes. The assembly of COPI vesicles is initiated by the recruitment of adenosine diphosphate-ribosylation factor 1 (Arf1) to the membrane. Previous studies have primarily focused on the roles of COPI in yeast, humans, insects, and beyond Drosophila. However, the function of COPI during the development of insects remains largely unknown. In this study, we first identified eight COPI assembly genes, including α-, β-, β'-, γ-, δ-, ε-, ζ-COPI, and Arf1 in Locusta migratoria. Quantitative reverse-transcription polymerase chain reaction revealed that these genes were uniformly expressed in multiple tissues, including wing pads, leg, foregut, midgut, hindgut, and gastric cecum, and on all developmental days in 5th-instar nymphs. The injection of double-stranded RNAs (dsRNAs) against LmCOPI and LmArf1 induced high silencing efficiency in the 3rd- and 5th-instar nymphs. Locusts treated with dsLmCOPIs and dsLmArf1 exhibited feeding cessation, leading to 100 % mortality. LmCOPIs and LmArf1 knockdown resulted in midgut and gastric cecum atrophy. Histological observation and hematoxylin-eosin staining indicated that the midgut and gastric cecum exhibited deformed structures, with defective microvilli and midgut peritrophic matrix. These results suggest that LmCOPIs and LmArf1 significantly affect the intestinal tract morphogenesis in locust nymphs. Thus, COPI assembly genes are promising RNA interference targets for managing L. migratoria, reducing the dependence on chemical pesticides for pest control.

Functions of Insulin-like Peptide Genes (CsILP1 and CsILP2) in Female Reproduction of the Predatory Ladybird Coccinella septempunctata (Coleoptera: Coccinellidae)

Insulin-like peptides (ILPs) are important peptide hormones in insects, particularly involved in regulating physiological processes such as growth, development, and reproduction. However, the specific roles of ILPs in the reproduction of natural enemy insects remain unknown. In this study, two ILP genes, CsILP1 and CsILP2, were cloned and their functions were analyzed in female Coccinella septempunctata L. (Coleoptera: Coccinellidae). The open reading frames (ORFs) of CsILP1 and CsILP2 were 384 bp and 357 bp, respectively. The expression of CsILP1 increased on the 6th day after eclosion, reaching its peak on the 12th day, while CsILP2 levels showed a significant increase on the 6th day and then stabilized. In different tissues, CsILP1 was highly expressed in ovaries, while CsILP2 predominated in elytra. Injection of dsRNA targeting CsILP1 and CsILP2 resulted in the down-regulation of insulin pathway genes. The relative expression of ovarian development-related genes Vasa, G2/M, and Vg was reduced by 82.50%, 89.55%. and 96.98% in dsCsILP1-treated females, and by 42.55%, 91.36%, and 55.63% in dsCsILP2-treated females. Furthermore, substantial decreases in 14-day fecundity were observed, with reductions of 89.99% for dsCsILP1 and 83.45% for dsCsILP2. These results confirm the regulatory functions of CsILP1 and CsILP2 in female C. septempunctata reproduction.

De novo transcriptome assembly and differential gene expression analysis in different developmental stages of Agriotes sputator (click beetle)

Wireworms, the larva of click beetle (Agriotes species), are one of the most destructive pests of horticultural crops in North America, responsible for considerable economic losses in Canada. Agriotes sputator (A. sputator) species is a predominant wireworm pest attacking potato fields in Eastern Canada. However, no information about its genome-wide gene expression profile, specifically for the genes involved with development is available to date. Therefore, we generated the transcriptome profile of A. sputator during five developmental stages, including the three larval stages and adult male and female click beetle. Out of 714.7 million raw reads, de novo assembly generated 564,561 transcripts. The data were subjected to differential expression analysis using DESeq2, gene ontology, annotation, and pathway analyses. A total of 34,709 differentially expressed genes (DEGs) were significant (log2 fold change > 2, padj < 0.05) across the developmental stages. Functional analysis of DEGs identified development signaling, metabolism, transport, cellular mechanisms, and drug metabolism (cytochrome p450) pathways. This study provides comprehensive sequence resources and potential gene differences at different developmental stages of A. sputator. These findings will represent a major step towards developing sustainable methods to control this widely distributed pest in agricultural fields.

RNA interference-mediated silencing of coat protein II (COPII) genes affects the gut homeostasis and cuticle development in Locusta migratoria

The coat protein II (COPII) complex consists of five primary soluble proteins, namely the small GTP-binding protein Sar1, the inner coat Sec23/Sec24 heterodimers, and the outer coat Sec13/Sec31 heterotetramers. COPII is essential for cellular protein and lipid trafficking through cargo sorting and vesicle formation at the endoplasmic reticulum. However, the roles of COPII assembly genes remain unknown in insects. In present study, we identified five COPII assembly genes (LmSar1, LmSec23, LmSec24, LmSec13 and LmSec31) in Locusta migratoria. RT-qPCR results revealed that these genes showed different expression patterns in multiple tissues and developmental days of fifth-instar nymphs. Injection of double-stranded RNA against each LmCOPII gene induced a high RNAi efficiency, and considerably suppressed feeding, and increased mortality to 100 %. Results from the micro-sectioning and hematoxylin-eosin staining of midguts showed that the brush border was severely damaged and the number of columnar cells was significantly reduced in dsLmCOPII-injected nymphs, as compared with the control. The dilated endoplasmic reticulum phenotype of columnar cells was observed by transmission electron microscopy. RT-qPCR results further indicated that silencing any of the five genes responsible for COPII complex assembly repressed the expression of genes involved in insulin/mTOR-associated nutritional pathway. Therefore, COPII assembly genes could be promising RNAi targets for insect pest management by disrupting gut and cuticle development.

Lethal and sublethal effects of orally delivered double-stranded RNA on the cabbage stem flea beetle, Psylliodes chrysocephala

BACKGROUND

The cabbage stem flea beetle (Psylliodes chrysocephala) is one of the most important insect pests of oilseed rape (Brassica napus) in northern Europe. The emergence of insecticide-resistant populations and the ban on neonicotinoid seed treatments have made the management of this pest challenging and research is needed to develop alternative strategies such as RNA interference (RNAi). We investigated lethal and sublethal effects of orally delivered double-stranded (ds)RNAs targeting P. chrysocephala orthologs of Sec23 and vacuolar adenosine triphosphatase subunit G (VatpG), which are involved in endoplasmic reticulum-Golgi transport and organelle acidification, respectively.

RESULTS

Feeding bioassays on P. chrysocephala adults showed that the highest concentration (200 ng/leaf disk) of dsSec23 caused mortalities of 76% and 56% in pre-aestivating and post-aestivating beetles, respectively, while the same concentration of dsVatpG led to mortality rates of ~34% in both stages. Moreover, sublethal effects, such as decreased feeding rates and attenuated locomotion were observed. Small RNA sequencing and gene expression measurements following the delivery of dsRNAs demonstrated the generation of ~21 nucleotide-long small interfering RNAs and a systemic RNAi response in P. chrysocephala.

CONCLUSION

We demonstrate that P. chrysocephala is a promising candidate for developing RNAi-based pest management strategies. Further research is necessary to identify more effective target genes and to assess potential non-target effects. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Knockdown of Sec16 causes early lethality and defective deposition of the protein Rp30 in the eggshell of the vector Rhodnius prolixus

In nearly every species of insect, embryonic development takes place outside of the mother's body and is entirely dependent on the elements that the mother had previously stored within the eggs. It is well known that the follicle cells (FCs) synthesize the eggshell (chorion) components during the process of choriogenesis, the final step of oogenesis before fertilization. These cells have developed a specialization in the massive production of chorion proteins, which are essential for the protection and survival of the embryo. Here, we investigate the function of Sec16, a protein crucial for the endoplasmic reticulum (ER) to Golgi traffic, in the oocyte development in the insect Rhodnius prolixus. We discovered that Sec16 is strongly expressed in vitellogenic females' ovaries, particularly in the choriogenic oocyte and it is mainly associated with the FCs. Silencing of Sec16 by RNAi caused a sharp decline in oviposition rates, F1 viability, and longevity in adult females. In the FCs, genes involved in the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and autophagy were massively upregulated, whereas the mRNAs of Rp30 and Rp45-which code for the two major chorion proteins - were downregulated as a result of Sec16 silencing, indicating general proteostasis disturbance. As a result, the outer surface ultrastructure of Sec16-silenced chorions was altered, with decreased thickness, dityrosine crosslinking, sulfur signals, and lower amounts of the chorion protein Rp30. These findings collectively demonstrate the critical role Sec16 plays in the proper functioning of the FCs, which impacts the synthesis and deposition of particular components of the chorion as well as the overall reproduction of this vector.

RNA interference against the putative insulin receptor substrate gene IRS1 affects growth and development in the pest natural enemy Pardosa pseudoannulata

BACKGROUND

Insulin signalling pathways play crucial roles in regulating growth and development in insects, but their effects on the growth and development of Arachnids, such as spiders, have rarely been studied. As a valuable pest natural enemy in agricultural fields, the molecular mechanisms of insulin signalling pathway-mediated growth and development of the wolf spider, Pardosa pseudoannulata, are of particular interest.

RESULTS

In this study, we identified and characterized six insulin signalling pathway genes - InR, InR2, IRS1, PI3K1, PI3K2, and PDK - in Pardosa pseudoannulata. Real-time quantitative polymerase chain reaction results were used to analyse the relative expression levels of the six genes in different developmental instars and tissues, and in response to starvation treatment. In addition, the function of the insulin receptor substrate (IRS1) gene was investigated using RNA interference technology, which found that IRS1 significantly influenced nutrient content, developmental duration, body weight, and gonad development.

CONCLUSION

This study revealed the roles of six key insulin signalling pathway genes in Pardosa pseudoannulata, and in particular the importance of the IRS1 gene in regulating growth and development in the spider. The results lay the foundation for further research on the internal regulation mechanisms of growth and development in Araneae species, and also provide a reference for the artificial breeding of spiders. © 2023 Society of Chemical Industry.

RNAi-Mediated Functional Analysis Reveals the Regulation of Oocyte Vitellogenesis by Ecdysone Signaling in Two Coleoptera Species

Coleoptera is the largest taxa of animals by far. The robust reproductive capacity is one of the main reasons for such domination. Successful female reproduction partially relies on effective vitellogenesis. However, the hormone regulation of vitellogenesis remains to be explored. In the present paper, in vitro culture of Leptinotarsa decemlineata 1-day-old adult fat bodies in the 20E-contained median did not activate juvenile hormone production and insulin-like peptide pathways, but significantly stimulated the expression of two LdVg genes, in a cycloheximide-dependent pattern. In vivo RNA interference (RNAi) of either ecdysone receptor (LdEcR) or ultraspiracle (Ldusp) by injection of corresponding dsRNA into 1-day-old female adults inhibited oocyte development, dramatically repressed the transcription of LdVg genes in fat bodies and of LdVgR in ovaries; application of JH into the LdEcR or Ldusp RNAi L. decemlineata females did not restore the oocyte development, partially rescued the decreased LdVg mRNA levels but over-compensated LdVgR expression levels. The same RNAi experiments were performed in another Coleoptera species, Henosepilachna vigintioctopunctata. Little yolk substances were seen in the misshapen oocytes in the HvEcR or Hvusp RNAi ovaries, in contrast to larger amounts of yolk granules in the normal oocytes. Correspondingly, the transcript levels of HvVg in the fat bodies and ovaries decreased significantly in the HvEcR and Hvusp RNAi samples. Our results here show that 20E signaling is indispensable in the activation of vitellogenesis in the developing oocytes of the two beetle species.

Sar1 Interacts with Sec23/Sec24 and Sec13/Sec31 Complexes: Insight into Its Involvement in the Assembly of Coat Protein Complex II in the Microsporidian Nosema bombycis

Microsporidia, as unicellular eukaryotes, also have an endomembrane system for transporting proteins, which is essentially similar to those of other eukaryotes. In eukaryotes, coat protein complex II (COPII) consists of Sar1, Sec23, Sec24, Sec13, and Sec31 and mediates protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus. Sar1 is the central player in the regulation of coat protein complex II vesicle formation in the endoplasmic reticulum. In this study, we successfully cloned the NbSar1, NbSec23-1, NbSec23-2, NbSec24-1, NbSec24-2, NbSec13, NbSec31-1, and NbSec31-2 genes and prepared NbSar1 polyclonal antibody. We found that NbSar1 was localized mainly in the perinuclear cytoplasm of Nosema bombycis by immunofluorescence analysis (IFA). Yeast two-hybrid assays demonstrated that NbSar1 interacts with NbSec23-2, NbSec23-2 interacts with NbSec24-1 or NbSec24-2, NbSec23-1 interacts with NbSec31, and NbSec31 interacts with NbSec13. Moreover, the silencing of NbSar1 by RNA interference resulted in the aberrant expression of NbSar1, NbSec23-1, NbSec24-1, NbSec24-2, NbSec13, NbSec31-1, and NbSec31-2 and significantly inhibited the proliferation of N. bombycis. Altogether, these findings indicated that the subunits of coat protein complex II work together to perform functions in the proliferation of N. bombycis and that NbSar1 may play a crucial role in coat protein complex II vesicle formation. IMPORTANCE As eukaryotes, microsporidia have retained the endomembrane system for transporting and sorting proteins throughout their evolution. Whether the microsporidia form coat protein complex II (COPII) vesicles to transport cargo proteins and whether they play other roles besides cargo transport are not fully explained at present. Our results showed that NbSar1, NbSec23-1/NbSec23-2, NbSec24-1/NbSec24-2, NbSec13, and NbSec31 might be assembled to form COPII in the ER of N. bombycis, and the functions of COPII are also closely related to the proliferation of N. bombycis, this may be a new target for the prevention of pébrine disease of the silkworm.