Characterization and expression profiling of G protein-coupled receptors (GPCRs) in Spodoptera litura (Lepidoptera: Noctuidae)

Evolutionary origin and distribution of leucine-rich repeat-containing G protein-coupled receptors in insects

Leucine-rich repeat-containing G protein-coupled receptors (LGRs) are crucial for animal growth and development. They were categorized into four types (A, B, C1, and C2) based on their sequence and domain structures. Despite the widespread distribution of LGRs across bilaterians, a thorough investigation of their distribution and evolutionary history remains elusive. Recent studies insect LGRs, especially the emergence of type C2 LGRs in various hemimetabolous insects, had prompted our study to address these problems. Initially, we traced the origins of LGRs by exploiting data from 99 species spanning 11 metazoan phyla, and discovered that type A and B LGRs originated from sponges, while type C LGRs originated from cnidarians. Subsequently, through comprehensive genomic and transcriptomic analyses across 565 species across 25 orders of insects, we found that both type A and C1 LGRs divided into two gene clusters. These clusters can be traced back to basal Insecta and an early ancestor of the Arthropoda, respectively. Furthermore, the absence of type B LGRs in wingless insects suggests a role in wing development, while the absence of type C2 LGRs in holometabolous insects hints at novel functions unrelated to insect metamorphosis. According to the origin of LGRs and the investigation of LGRs in insects, we speculated that type A and B LGRs appeared first among four types of LGRs, type A evolved into type C LGRs later, and type A and C1 LGRs independently duplicated during the evolutionary process. This study provides a more comprehensive view of the evolution of LGR genes than previously available, and sheds light on the evolutionary history and significance of LGRs in insect biology.

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.

Identification of G Protein-Coupled Receptors (GPCRs) Associated with Lambda-Cyhalothrin Detoxification in Cydia pomonella

While previous studies have reported G protein-coupled receptor (GPCR)-mediated insecticide resistance in various arthropods, the understanding of GPCR-associated resistance mechanisms in Cydia pomonella remains limited. In this study, a total of 95 CpGPCR genes categorized into four families were identified in C. pomonella. Results revealed high expression levels of the majority of the CpGPCRs during the first larval stage and in the head of C. pomonella. Exposure to lambda-cyhalothrin significantly increased the expression of 15 CpGPCRs, including CpGPCR70, which is highly expressed in all larval stages and shows the highest expression in the midgut. RNA interference (RNAi) demonstrated that downregulation of CpGPCR70 leads to reduced expression of key resistance-related genes and a decreased tolerance of larvae to lambda-cyhalothrin. These findings indicate that CpGPCR70 plays a crucial role in regulating the expression of detoxifying genes involved in lambda-cyhalothrin resistance, offering valuable insights for the development of more effective pest control strategies.

The Jinggangmycin-induced Mthl2 gene regulates the development and stress resistance in Nilaparvata lugens Stål (Hemiptera: Delphacidae)

Methuselah (Mth) belongs to the GPCR family B, which regulates various biological processes and stress responses. The previous transcriptome data showed jinggangmycin (JGM)-induced Mthl2 expression. However, its detailed functional role remained unclear in brown planthopper, Nilaparvata lugens Stål. In adult N. lugens, the Mthl2 gene showed dominant expressions, notably in ovaries and fat body tissues. The 3rd instar nymphs treated with JGM increased starvation, oxidative stress, and high temperature (34 °C) tolerance of the adults. On the contrary, under dsMthl2 treatment, completely opposite phenotypes were observed. The lipid synthesis genes (DGAT1and PNPLA3) of both females and males treated with JGM in the nymphal stage were observed with high expressions, while the lipolysis of the Lipase 3 gene was observed with low expressions. The JGM increased triglyceride (TG) content, fat body droplet size, and the number of fat body droplets. The same treatment also increased the Glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) activities. An increase in the heat shock protein (HSP70 and HSP90) expression levels was also observed under JGM treatment but not dsMthl2. The current study demonstrated the influential role of the Mthl genes, particularly the Mthl2 gene, in modulating the growth and development and stress-responsiveness in N. lugens. Thus, providing a platform for future applied research programs controlling N. lugens population in rice fields.