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

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.