microRNA-34-5p encoded by Spodoptera frugiperda regulates the replication and infection of Autographa californica multiple nucleopolyhedrovirus by targeting odv-e66, ac78 and ie2

microRNA-34 family: A multifunctional miRNA family

MicroRNAs are endogenous non-coding small RNAs composed of about 22 nucleotides, which are widely found in eukaryotic cells and regulate gene expression at the post-transcriptional level through complementary pairing with target genes, leading to mRNA degradation or translation inhibition. MiR-34 family is a highly conserved miRNA family during evolution. Recent studies have found that members of the miR-34 family are involved in regulating biological processes such as aging, ciliogenesis, and immunity. To have a more comprehensive understanding of miR-34 family, this paper reviewed the functional evolution of miR-34 family, and provided a reference for further research on the related functions of miR-34.

Indole-diterpenoids from an endophytic Penicillium brefeldianum F4a and their antifeedant and insecticidal activities against Spodoptera frugiperda

BACKGROUND

Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the world's major agriculture pests, causing significant crop damage and serious economic losses. As S. frugiperda has developed widespread resistance, environmentally friendly insecticides are urgently needed. Therefore, searching for natural antifeedant or insecticidal lead compounds has become imperative.

RESULTS

Three new indole diterpenoids, paspamine A (1), paspamine B (2), and paspalitrem D (3), along with nine known ones (compounds 4-12), were isolated from an endophytic Penicillium brefeldianum F4a. Their structures were identified through comprehensive spectroscopic data analysis [one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), ultraviolet (UV), infrared (IR)], and electronic circular dichroism (ECD) calculations. Furthermore, plausible biosynthetic pathways of these compounds were deduced. The bioassay results indicated that compound 8 displayed more significant antifeedant activity against S. frugiperda larvae than azadirachtin and compounds 5-7 demonstrated superior insecticidal activities compared to abamectin. Moreover, comparative transcriptome analysis revealed that compound 6 exerted a distinct insecticidal mechanism. In the early stages, it regulated the expression of genes associated with peptidases and chitinases. Subsequently, this regulation influenced the expression of genes related to cuticle proteins and other relevant genes, ultimately resulting in S. frugiperda larval death. These results were further confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) experiments.

CONCLUSION

This research will provide valuable information for the development of indole diterpenoids as novel microbial insecticides for the management of S. frugiperda. © 2025 Society of Chemical Industry.

miR-9a and miR-10482-5p regulate the expression of chitin synthase and chitinase genes, enhancing lufenuron tolerance in Spodoptera frugiperda

Spodoptera frugiperda is a significant agricultural pest, severely impacting the yield and quality of grain. Chitin is the momentous component of exoskeletons, which has a significant impact on the growth and development of insects. Our previous study found that exposure to lufenuron can reduce the expression of chitinase gene (SfCHT5) and increase the expression of chitin synthase gene (SfCHSB), two key genes for chitin synthesis in S. frugiperda. However, the post-transcriptional regulatory mechanisms of these key genes in S. frugiperda remain unclear. With miRNA as the entry point, target site prediction, dual luciferase reporter assays, and mimics/inhibitors injection were used to explore the post-transcriptional regulatory mechanism of SfCHSB and SfCHT5. The combined results confirm that miR-10482-5p targets SfCHT5 and regulates its expression, while miR-9a targets and regulates the expression of both SfCHT5 and SfCHSB. Additionally, injection of miR-10482-5p and miR-9a mimic significantly reduced the mortality rates of S. frugiperda treated with lufenuron, increased pupation rate, and emergence rate. These findings underscore the critical regulatory role of miR-10482-5p and miR-9a in modulating the expression of key genes involved in chitin synthesis, thereby enhancing the tolerance of S. frugiperda to lufenuron and influencing its growth and development. In summary, this study preliminarily elucidates the post-transcriptional regulatory mechanisms of miRNA-mediated SfCHSB and SfCHT5 expression.

Epigenetic Regulation in Insect-Microbe Interactions

Insects have evolved diverse interactions with a variety of microbes, such as pathogenic fungi, bacteria, and viruses. The immune responses of insect hosts, along with the dynamic infection process of microbes in response to the changing host environment and defenses, require rapid and fine-tuned regulation of gene expression programs. Epigenetic mechanisms, including DNA methylation, histone modifications, and noncoding RNA regulation, play important roles in regulating the expression of genes involved in insect immunity and microbial pathogenicity. This review highlights recent discoveries and insights into epigenetic regulatory mechanisms that modulate insect-microbe interactions. A deeper understanding of these regulatory mechanisms underlying insect-microbe interactions holds promise for the development of novel strategies for biological control of insect pests and mitigation of vector-borne diseases.

Cnaphalocrocis medinalis granulovirus regulates apoptosis by targeting AIF1 and ASPP1 through tca-miR-3885-5p and tca-miR-3897-3p to promote infection

Cnaphalocrocis medinalis granulovirus (CnmeGV) is a potential biocontrol agent for C. medinalis which is a major rice pest. However, its insecticidal efficacy is slow due to cell apoptosis. This study investigated the role of miRNAs in CnmeGV-mediated apoptosis. Small RNA sequencing and qRT-PCR identified miRNAs tca-miR-3885-5p and tca-miR-3897-3p, which initially increased and then decreased post-infection, but remained higher than controls. This trend was opposite to the changes in midgut apoptosis levels detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and DNA ladder assays. Compared to the group treated with CnmeGV alone, agomirs increased the CnmeGV-induced larval mortality, reduced midgut apoptosis, whereas antagomirs had the opposite effects. We found that the upregulation of CnmeGV replication induced by agomirs initially increased and then decreased, while the apoptosis inducer PAC-1 compensated for the weakening trend of CnmeGV replication upregulation induced by agomirs in the later stages of infection. Results indicated the virus hijacks these miRNAs to inhibit early apoptosis, later requiring apoptosis for systemic infection from the midgut. Agomirs treatment and dual-luciferase assays showed these miRNAs functioned via apoptosis-inducing factor 1 (AIF1) and apoptosis-stimulating protein of p53 1 (ASPP1) mRNA expression. This study highlights the role of these miRNAs in infection and provides insights for developing viral insecticide enhancers.

Functional regulation of microRNA-184 in the replication and infection of Autographa californica multiple nucleopolyhedrovirus

MicroRNAs (miRNAs) represent a class of short, non-coding RNAs that are widely acknowledged as crucial participants in virus-host interactions. MiR-184, a highly conserved and abundant miRNA in insects, has yet to be extensively studied for its involvement in baculovirus infection. In this study, we investigated how miR-184 affects the infection and replication of Autographa californica multiple nucleopolyhedrovirus (AcMNPV). The results indicated that after AcMNPV infection, there was an initial increase in the expression of miR-184 within 24 h, followed by a subsequent decrease. MiR-184 can inhibit AcMNPV's DNA replication and budded virus production by directly targeting four viral genes, namely ie1, ac66, p49, and lef9. Moreover, suppressing miR-184 expression enhanced the insecticidal efficacy of AcMNPV against Spodoptera exigua larvae and markedly elevated the host ATPase gene expressions. These findings showed that miR-184 had a substantial impact on the interactions between baculoviruses and insects, presenting a prospective candidate for developing highly effective miRNA-based biopesticides.

MicroRNA-Mediated Host Immune Genes Manipulation Benefits AcMNPV Proliferation in Spodoptera frugiperda

Spodoptera frugiperda is a highly destructive migratory pest that threatens various crops globally. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is an effective biocontrol agent against lepidopteran pests. Here, we explored the molecular mechanisms underlying the immune response to AcMNPV infection in S. frugiperda. RNA-seq and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses identified the Toll, IMD, and apoptosis pathways as primary immune responses. Investigation into AcMNPV-induced apoptosis in the S. frugiperda cell line (Sf9) revealed that the Toll pathway activated the JNK via the TRAF6 (TNF receptor-associated factor 6) adapter. In addition, AcMNPV-induced the differential expression of several host-encoded microRNAs (miRNAs), with significant negative regulatory effects, on S. frugiperda antiviral immune genes. RNAi and miRNA-mimic mediated silencing of these genes resulted in increased AcMNPV proliferation. Our findings reinforce the potential of AcMNPV as a potent biocontrol agent and further our understanding of developing biotechnology-based targeted pest control agents.

Four antimicrobial peptides of Asian gypsy moth respond to infection of its viral pathogen, nucleopolyhedrovirus (LdMNPV)

Antimicrobial peptides (AMPs) play essential roles in defending against various invading pathogens. Although antibacterial or antifungal properties of AMPs have been well characterized, the contribution of AMPs to immune defenses against viruses especially baculoviruses is still unclear. In this study, four full-length AMP genes (Ldcec, Ldatt, Ldglo and Ldmor) that encode the cecropin, attacin, gloverin and moricin, respectively, were characterized in Lymantria dispar (Asian gypsy moth). All four AMPs were cationic peptides and exhibited hydrophilicity. Structural analysis showed that the Ldcec and Ldmor were α-helical peptides. Tissue-specific Ldcec expression was the highest in fat body, while expression of Ldatt, Ldglo and Ldmor was the highest in epidermis. All four AMP genes were expressed during all developmental stages with the highest expression in the pupa and adult. Compared to mock infection, expression of these four AMP genes were significantly induced following Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) challenge and sharply increased at 72 h post infection. After Ldglo gene silencing, the DNA replication levels of LdMNPV in L. dispar larvae significantly increased at 48 and 72 h post infection, indicating that the Ldglo could suppress the DNA replication of LdMNPV. Our results suggest that four AMPs of L. dispar may play important roles in antiviral immunity against LdMNPV.