Genomics, transcriptomics, and peptidomics of Spodoptera frugiperda (Lepidoptera, Noctuidae) neuropeptides

Neuropeptide natalisin regulates reproductive behaviors in Spodoptera frugiperda

Natalisin (NTL) is a conserved neuropeptide, only present in insects, that has been reported to regulate their sexual activity. In this study, we investigated the involvement of NTL in the reproductive behaviors of a major invasive pest, Spodoptera frugiperda. We identified NTL precursor-encoded transcripts, and evaluated their transcript levels in different stages and tissues of S. frugiperda. The results showed that the NTL transcript level was expressed in both male and female pupae and both male and female adults in the later stage. It was highly expressed in male pupae, 3-day-old male and female adults, and 5-day-old male adults. In different tissues, the expression level is higher in the male and female adult brain and male testis. Immunohistochemical staining of the brain of S. frugiperda female and male adults revealed that three pairs of brain neurons of S. frugiperda adults of both sexes secreted and expressed NTL. To study the role of NTL in reproductive behaviors, NTL was silenced in S. frugiperda male and female adults by RNA interference (RNAi) technology, the results showed that silencing NTL could significantly affect the sexual activity behavior of the adults, reducing the calling rate of females, the courtship rate of males, and the mating rate. In summary, this study emphasizes the important role of NTL in regulating the mating behavior and sexual activity of S. frugiperda in both male and female adults, potentially laying a foundation to employ NTL as a new insect-specific target to control populations of pest insects.

Genomics, transcriptomics, and peptidomics of the greater wax moth Galleria mellonella neuropeptides and their expression in response to lead stress

Neuropeptides are crucial in regulation of a rich variety of developmental, physiological, and behavioral functions throughout the life cycle of insects. Using an integrated approach of multiomics, we identified neuropeptide precursors in the greater wax moth Galleria mellonella, which is a harmful pest of honeybee hives with a worldwide distribution. Here, a total of 63 and 67 neuropeptide precursors were predicted and annotated in the G. mellonella genome and transcriptome, in which 40 neuropeptide precursors were confirmed in the G. mellonella peptidome. Interestingly, we identified 12 neuropeptide precursor genes present in G. mellonella but absent in honeybees, which may be potential novel pesticide target sites. Honeybee hives were contaminated with heavy metals such as lead, enabling its bioaccumulation in G. mellonella bodies through the food chain, we performed transcriptome sequencing to analyze the effects of Pb stress on the mRNA expression level of G. mellonella neuropeptide precursors. After treatment by Pb, the expression of neuropeptide F1 was found to be significantly downregulated, implying that this neuropeptide might be associated with responding to the heavy metal stress in G. mellonella. This study comprehensively identified neuropeptide precursors in G. mellonella, and discussed the effects of heavy metals on insect neuropeptides, with the example of G. mellonella. The results are valuable for future elucidation of how neuropeptides regulate physiological functions in G. mellonella and contribute to our understanding of the insect's environmental plasticity and identify potential new biomarkers to assess heavy metal toxicity in insects.

Characterization of Neuropeptides from Spodoptera litura and Functional Analysis of NPF in Diet Intake

Neuropeptides are involved in many biological processes in insects. However, it is unclear what role neuropeptides play in Spodoptera litura adaptation to phytochemical flavone. In this study, 63 neuropeptide precursors from 48 gene families were identified in S. litura, including two neuropeptide F genes (NPFs). NPFs played a positive role in feeding regulation in S. litura because knockdown of NPFs decreased larval diet intake. S. litura larvae reduced flavone intake by downregulating NPFs. Conversely, the flavone intake was increased if the larvae were treated with NPF mature peptides. The NPF receptor (NPFR) was susceptible to the fluctuation of NPFs. NPFR mediated NPF signaling by interacting with NPFs to regulate the larval diet intake. In conclusion, this study suggested that NPF signaling regulated diet intake to promote S. litura adaptation to flavone, which contributed to understanding insect adaptation mechanisms to host plants and provide more potential pesticidal targets for pest control.

The genome and sex-dependent responses to temperature in the common yellow butterfly, Eurema hecabe

BACKGROUND

Lepidoptera (butterflies and moths) is one of the most geographically widespread insect orders in the world, and its species play important and diverse ecological and applied roles. Climate change is one of the biggest challenges to biodiversity this century, and lepidopterans are vulnerable to climate change. Temperature-dependent gene expression differences are of relevance under the ongoing climate crisis. However, little is known about how climate affects gene expression in lepidopterans and the ecological consequences of this, particularly with respect to genes with biased expression in one of the sexes. The common yellow butterfly, Eurema hecabe (Family Pieridae), is one of the most geographically widespread lepidopterans that can be found in Asia, Africa, and Australia. Nevertheless, what temperature-dependent effects there may be and whether the effects differ between the sexes remain largely unexplored.

RESULTS

Here, we generated high-quality genomic resources for E. hecabe along with transcriptomes from eight developmental stages. Male and female butterflies were subjected to varying temperatures to assess sex-specific gene expression responses through mRNA and microRNA transcriptomics. We find that there are more temperature-dependent sex-biased genes in females than males, including genes that are involved in a range of biologically important functions, highlighting potential ecological impacts of increased temperatures. Further, by considering available butterfly data on sex-biased gene expression in a comparative genomic framework, we find that the pattern of sex-biased gene expression identified in E. hecabe is highly species-specific, rather than conserved across butterfly species, suggesting that sex-biased gene expression responses to climate change are complex in butterflies.

CONCLUSIONS

Our study lays the foundation for further understanding of differential responses to environmental stress in a widespread lepidopteran model and demonstrates the potential complexity of sex-specific responses of lepidopterans to climate change.

Peptidomics Methods Applied to the Study of Flower Development

Understanding the global and dynamic nature of plant developmental processes requires not only the study of the transcriptome, but also of the proteome, including its largely uncharacterized peptidome fraction. Recent advances in proteomics and high-throughput analyses of translating RNAs (ribosome profiling) have begun to address this issue, evidencing the existence of novel, uncharacterized, and possibly functional peptides. To validate the accumulation in tissues of sORF-encoded polypeptides (SEPs), the basic setup of proteomic analyses (i.e., LC-MS/MS) can be followed. However, the detection of peptides that are small (up to ~100 aa, 6-7 kDa) and novel (i.e., not annotated in reference databases) presents specific challenges that need to be addressed both experimentally and with computational biology resources. Several methods have been developed in recent years to isolate and identify peptides from plant tissues. In this chapter, we outline two different peptide extraction protocols and the subsequent peptide identification by mass spectrometry using the database search or the de novo identification methods.

Systematic identification and characterization of differentially expressed microRNAs under tetraniliprole exposure in the fall armyworm, Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a worldwide agricultural pest and causes huge losses of crop production each year. Tetraniliprole is a novel diamide insecticide with high efficacy against even the insecticide resistant pests of Lepidoptera, Coleoptera, and Diptera. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level and play an important regulatory role in the insecticide resistance in insects. However, the effects of miRNAs on the tetraniliprole tolerance in S. frugiperda are poorly understood. In the present research, the miRNAs response to tetraniliprole application in S. frugiperda were systematically investigated by high-throughput sequencing. A total of thirty differentially expressed miRNAs were identified under tetraniliprole treatment in S. frugiperda. The functions of the target genes of these differentially expressed miRNAs were further predicted by Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes database pathway, and the most significantly enriched pathway was MAPK signaling pathway. The expression changes of six differentially expressed miRNAs were validated by quantitative real-time polymerase chain reaction. Furthermore, miR-278-5p had the highest expression in the hemolymph and malpighian tubule and the lowest expression in the gut. Oversupply of miR-278-5p significantly increased the mortality of S. frugiperda following exposure to tetraniliprole. These results will provide the basis for understanding the regulatory roles of miRNAs regarding to tetraniliprole tolerance in S. frugiperda.

Identification and characterization of G protein-coupled receptors in Spodoptera frugiperda (Insecta: Lepidoptera)

Spodoptera frugiperda (Insecta: Lepidoptera) is a destructive invasive pest feeding on various plants and causing serious damage to several economically-important crops. G protein-coupled receptors (GPCRs) are cellular receptors that coordinate diverse signaling processes, associated with many physiological processes and disease states. However, less information about GPCRs had been reported in S. frugiperda, limiting the recognition of signaling system and in-depth studies of this pest. Here, a total of 167 GPCRs were identified in S. frugiperda. Compared with other insects, the GPCRs of S. frugiperda were significantly expanded. A large of tandem duplication and segmental duplication events were observed, which may be the key factor to increase the size of GPCR family. In detail, these expansion events mainly concentrate on biogenic amine receptors, neuropeptide and protein hormone receptors, which may be involved in feeding, reproduction, life span, and tolerance of S. frugiperda. Additionally, 17 Mth/Mthl members were identified in S. frugiperda, which may be similar to the evolutionary pattern of 16 Mth/Mthl members in Drosophila. Moreover, the expression patterns across different developmental stages of all GPCR genes were also analyzed. Among these, most of the GPCR genes are poorly expressed in S. frugiperda and some highly expressed GPCR genes help S. frugiperda adapt to the environment better, such as Rh6 and AkhR. In this study, all GPCRs in S. frugiperda were identified for the first time, which provided a basis for further revealing the role of these receptors in the physiological and behavioral regulation of this pest.