Tyrosine hydroxylase involved in cuticle tanning and reproduction in the 28-spotted potato ladybeetle, Henosepilachna vigintioctopunctata

Knockdown of tyrosine hydroxylase gene affects larval survival, pupation and adult eclosion in Plagiodera versicolora

In insects, tyrosine hydroxylase (TH) plays essential roles in cuticle tanning and cuticle pigmentation. Plagiodera versicolora (Coleoptera: Chrysomelidae) is a leaf-eating forest pest in salicaceous trees worldwide. However, the function of PverTH in P. versicolora is still unknown. In this study, we obtained a PverTH gene from transcriptome analysis. The expression analysis of PverTH showed that the highest expression was found in epidermis of larvae. In this study, we used RNA interference (RNAi) technology to knockdown the PverTH gene. The results showed that ingestion of dsTH led to cuticle coloration became lighter in larvae, pupae and adults. Knockdown of PverTH gene inhibited larval growth, and consequently caused higher mortality. In addition, RNAi of TH disrupted the cuticle tanning, caused lower pupation rate, lower eclosion rate and higher deformity rate. This study indicates that PverTH is vital for the cuticular pigments and cuticle tanning. Moreover, this research suggested that the development of PverTH gene as a potential target gene to control P. versicolora.

HvStaufenC contributes to the high RNAi efficiency in the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata

RNA interference (RNAi) has been shown to be relatively effective in coleopteran insects, with limited exploration into the molecular mechanisms that underlie this effectiveness. This study specifically examines the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata (Hvig), known for its high RNAi efficiency. Here, we utilized RNAi and CRISPR/Cas9 techniques to identify and validate the genes involved in the RNAi pathway that enhance RNAi efficacy in Hvig. We identified a total of 15 potential genes within the RNAi pathway that may impact RNAi efficiency. The bioassay results showed that only knockdown of HvStaufenC in the 3rd instar larvae could block the abnormal body color phenotype and lethality induced by the subsequent silencing of the two marker genes, HvTH (tyrosine hydroxylase) and HvABCH1 (ATP-binding cassette H transporter gene), respectively. Additionally, successful CRISPR/Cas9-mediated knockout of HvStaufenC led to the generation of stable, heritable mutants that exhibited insensitivity to RNAi, displaying no response to RNAi targeting HvTH and HvABCH1. Compared to the wild-type strain, the HvStaufenC knockout (HvStaufenCKO) mutant females demonstrated a 42 % decrease in oviposition rate and a 41.3 % reduction in egg hatchability. This study demonstrates that HvStaufenC gene is crucial for the RNAi efficiency of Hvig and offers new evidence into the RNAi mechanisms in coleopteran species.

CRISPR/Cas9-mediated editing of the melanization gene ebony in the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata

The melanization process, which is essential for the proper functioning of the cuticle, has been extensively investigated for its enzymatic roles and physiological effects. Henosepilachna vigintioctopunctata, a significant pest species, presents considerable economic threats. However, due to the variable efficiency of RNA interference for genetic manipulation, establishing a CRISPR/Cas9 system is crucial for providing a more precise and reliable method for functional genomics in this non-model insect. In this study, we first utilized RNAi to investigate Hvebony, which encodes N-β-alanyldopamine, a critical compound in cuticle melanization. Subsequently, we introduced CRISPR/Cas9 for the first time in H. vigintioctopunctata. RNAi experiments revealed that knockdown of Hvebony resulted in abnormal melanin accumulation and low mortality rates, indicating its involvement in cuticle tanning. A novel CRISPR/Cas9 workflow was established, successfully resulting in the knocking out of Hvebony and the creation of a stable mutant strain characterized by dark pigmentation and low fitness costs. This study establishes Hvebony as a promising molecular marker for genetic studies in H. vigintioctopunctata. Moreover, it can be utilized in the development of genome editing control strategies and for analyses of gene function in H. vigintioctopunctata.

Foliar spray double-stranded RNA targeting HvIAP1 induces high larval and adult mortality in Henosepilachna vigintioctopunctata

BACKGROUND

Exogenous double-stranded RNA (dsRNA) has the potential to serve as an effective alternative to conventional chemical pesticides for the control of insect pests, because it can specifically inhibit essential gene expression in these organisms. However, identifying suitable gene targets remains a crucial step in the development of RNA interference (RNAi)-based pest control strategies.

RESULTS

In this study, three apoptosis-related genes were selected to evaluate their potential for RNAi-induced lethality in Henosepilachna vigintioctopunctata via foliar spray dsRNAs. Our results revealed that silencing of HvIAP1 (inhibitor of apoptosis protein 1) had a significant lethal effect on larvae, whereas silencing of HvAIF1 and HvASPP1 did not, correlating with distinct expression patterns. Larvae ingested leaves sprayed with bacterially expressed dsHvIAP1 at a concentration of 100 ng/cm2 resulting in the impairment of cuticle tanning, cessation of feeding, and ultimately, 100% mortality within 7 days. In addition, the potential of dsHvIAP1 to mediate for adult control was also investigated and showed that administration of 200 ng/cm2 dsHvIAP1 resulted in 100% adult mortality within 9 days, accompanied by a significant reduction in leaf consumption and suppression of HvIAP1 expression compared with the dsGFP group.

CONCLUSIONS

Our findings demonstrate that HvIAP1 is a highly lethal molecular target with a notable difference in the concentration required for larval and adult mortality. These findings provide a foundation for the future development of RNAi pesticides for environmentally friendly control of H. vigintioctopunctata. © 2025 Society of Chemical Industry.

Tyrosine Hydroxylase Is Required for the Larval-Pupal Transformation and Immunity of Plutella xylostella: Potential for Pest Management

Plutella xylostella has developed high levels of resistance to many commonly used insecticides. Tyrosine hydroxylase (TH) is essential for insect survival; thus, we evaluated whether TH could be a potential target for controlling P. xylostella. In this study, PxTH was identified; further qPCR analysis showed that PxTH increased its expression during larval pupation and was highly expressed in the head and epidermis of prepupa in P. xylostella. Subsequently, we found a significant decrease in insect pupation and eclosion rates after injection of dsPxTH or a feeding diet supplemented with 3-iodo-tyrosine (3-IT) as a TH inhibitor in P. xylostella. Moreover, this study suggested that PxTH enzyme activity and dopamine concentrations were significantly decreased, agreeing with the blockage of larval-pupal cuticle tanning, with thinner puparium and less melanization after feeding 3-IT. In addition, expression levels of four antimicrobial peptide genes were significantly inhibited after P. xylostella feeding with 3-IT, and injection of Escherichia coli resulted in 73.3% mortality, indicating that PxTH was required for immune responses. In summary, these results confirmed that PxTH was involved in the development and immunity of P. xylostella, suggesting a critical potential novel insecticide target for RNAi-based pest control.

Comparative Transcriptome Analysis of Henosepilachna vigintioctomaculata Reveals Critical Pathways during Development

Henosepilachna vigintioctomaculata is distributed in several Asian countries. The larvae and adults often cause substantial economic losses to Solanaceae crops such as potato, tomato, eggplant, and Chinese boxthorn. Even though a chromosome-level genome has been documented, the expression profiles of genes involved in development are not determined. In this study, we constructed embryonic, larval, pupal, and adult transcriptomes, generated a comprehensive RNA-sequencing dataset including ~52 Gb of clean data, and identified 602,773,686 cleaned reads and 33,269 unigenes. A total of 18,192 unigenes were successfully annotated against NCBI nonredundant protein sequences, Swissprot, Eukaryotic Orthologous Groups, Gene Ontology (GO), or Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. There were 3580, 2040, 5160, 2496, 3008, and 3895 differentially expressed genes (DEGs) between adult/egg, egg/larval, larval/pupal, adult/pupal, egg/pupal, and adult/larval samples, respectively. GO and KEGG analyses of the DEGs highlighted several critical pathways associated with specific developing stages. This is the first comprehensive transcriptomic dataset encompassing all developmental stages in H. vigintioctomaculata. Our data may facilitate the exploitation of gene targets for pest control and can serve as a valuable gene resource for future molecular investigations.

RNAi-based silencing of proteasome 20S subunit alpha 2 affected the survival and development of Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a notorious pest of solanaceous plants in Asia, which is mainly managed by chemical pesticides. RNA interference (RNAi) technique is considered to be a promising and effective alternative for pest control. In this study, we selected the proteasome 20S subunit alpha 2 (Prosα2) gene, a cellular protein involved in many proteins regulatory processes, to explore the RNAi efficiency in H. vigintioctopunctata. The obtained results confirmed the significant lethal effects of HvProsα2 silencing on the H. vigintioctopunctata 1st instar larvae at concentrations of 100, 50, and 5 ng/μL. Ingestion of the bacterially expressed dsHvProsα2 caused high mortality in both larvae and adults. Moreover, silencing of HvProsα2 resulted in feeding disorders, growth delay, and abnormal intestinal development of the larvae. Overall, HvProsα2 acts as an important regulator for the growth and development of H. vigintioctopunctata, and can serve as a candidate target gene for the RNAi-based control of H. vigintioctopunctata.

Unveiling Nilaparvata lugens Stål Genes Defining Compatible and Incompatible Interactions with Rice through Transcriptome Analysis and Gene Silencing

The brown planthopper (Nilaparvata lugens Stål, BPH) is a major pest of rice (Oryza sativa L.), causing severe crop loss. Multiple biotypes and emerging populations of BPH pose a bigger challenge for the infestations control. Although several studies have been conducted to understand the molecular mechanisms of rice-BPH interactions, there are few studies dedicated to the Indian sub-continent BPH biotype (biotype 4). Here, we analyzed the transcriptomic, physiological, and gene-silencing responses of the BPH biotype 4 during the compatible (fed on susceptible Taichung Native 1, TN1 rice) and incompatible (fed on resistant PTB33 rice) rice-BPH interactions. In the incompatible interaction, a significant reduction in the honeydew production and negative weight gain were observed in the BPH. Similarly, the trehalose and glucose contents were found to be significantly high and low, respectively, during the incompatible rice-BPH interaction. The comparative BPH transcriptome analysis identified 1875 differentially expressive genes (DEGs) between the compatible and incompatible interactions from which many were annotated to be involved in vital BPH physiological processes, including cuticle development, sugar metabolism, detoxification, molting, and xenobiotics metabolism. The RNA interference-mediated independent silencing of three selected genes, including NlCP1, NlCYP320a1, and NlTret1, revealed that these genes are important for BPH physiology and survival. Moreover, the results of this study provide valuable insights into the rice-BPH interactions involving the BPH biotype 4.

A comparative study revealed hyperspectral imaging as a potential standardized tool for the analysis of cuticle tanning over insect development

Cereal-feeding beetles are a major risk for cereal crop maintenance. Cereal weevils such as Sitophilus oryzae have symbiotic intracellular bacteria that provide essential aromatic amino acid to the host for the biosynthesis of their cuticle building blocks. Their cuticle is an important protective barrier against biotic and abiotic stresses, providing high resistance from insecticides. Quantitative optical methods specialized in insect cuticle analysis exist, but their scope of use and the repeatability of the results remain limited. Here, we investigated the potential of Hyperspectral Imaging (HSI) as a standardized cuticle analysis tool. Based on HSI, we acquired time series of average reflectance profiles from 400 to 1000 nm from symbiotic (with bacteria) and aposymbiotic (without bacteria) cereal weevils S. oryzae exposed to different nutritional stresses. We assessed the phenotypic changes of weevils under different diets throughout their development and demonstrated the agreement of the results between the HSI method and the classically used Red-Green-Blue analysis. Then, we compared the use of both technologies in laboratory conditions and highlighted the assets of HSI to develop a simple, automated, and standardized analysis tool. This is the first study showing the reliability and feasibility of HSI for a standardized analysis of insect cuticle changes.

RNAi-Based Biopesticides Against 28-Spotted Ladybeetle Henosepilachna vigintioctopunctata Does Not Harm the Insect Predator Propylea japonica

RNA interference (RNAi)-mediated control of the notorious pest Henosepilachna vigintioctopunctata is an emerging environment friendly research area. However, the characterization of key target genes in H. vigintioctopunctata is crucial for this. Additionally, assessing the risk of RNAi to nontarget organisms (NTOs) is necessary for environmental safety. In this study, the potential of RNAi technology in controlling H. vigintioctopunctata infestation has been investigated by the oral delivery of double-stranded RNA (dsRNA). The results revealed that the silencing of six genes, including HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k, was highly lethal to H. vigintioctopunctata. The LC50 values of the dsRNAs used to silence these six genes were found to be less than 13 ng/μL. Moreover, the use of the bacterially expressed dsRNAs caused high mortality in the lab and field populations of H. vigintioctopunctata. Further, administration of HvHel25E and HvSrp54k dsRNAs in the predatory lady beetle Propylea japonica confirmed no transcriptional or organismal levels effects. This risk-assessment result ensured no off-target RNAi effects on the NTOs. Overall, the findings of the study suggested that HvABCH1, HvHel25E, HvProsbeta5, HvProsalpha6, HvProsbeta6, and HvSrp54k can be novel promising molecular targets with high specificity for H. vigintioctopunctata management with negligible effects on the NTOs.