Hormone receptor 3 (HR3), an early-late gene of the 20-hydroxyecdysone (20E) signaling pathway, plays a critical role in insect metamorphosis and development. In this study, we identified and characterized an HR3 gene (LsHR3) from the cigarette beetle, Lasioderma serricorne. The open reading frame of LsHR3 is 1581 bp encoding a 527 amino acid protein that contains a conserved DNA binding domain and a ligand binding domain. LsHR3 was mainly expressed in the fourth-instar larvae, prepupae, and pupae and showed high expression in the fat body. The expression of LsHR3 was induced by 20E, while it was significantly suppressed by silencing of six 20E synthesis and signaling pathway genes. RNA interference (RNAi)-aided knockdown of LsHR3 in the fourth-instar larvae disrupted the larval–pupal molting and caused 100% mortality. The 20E titer of LsHR3-depletion larvae was decreased, and expressions of five 20E synthesis genes were dramatically decreased. Silencing LsHR3 reduced chitin content and downregulated the expression of genes involved in chitin synthesis and degradation. Hematoxylin and eosin staining of abdominal cuticle showed that no apolysis occurred after silencing LsHR3. These results suggest that LsHR3-mediated 20E signaling is involved in the regulation of chitin metabolism during the molting process of L. serricorne, and targeting this gene by RNAi has potential in controlling this pest.

Understanding plant-insect interactions can help control the harm of herbivorous pests. According to transcriptome data, transcripts of Solanum lycopersicum responding to feeding by Tuta absoluta were screened for important endopeptidase inhibitors. These genes were annotated as serine-type endopeptidase inhibitors from the potato inhibitor I family, potato type II proteinase inhibitor family, and soybean trypsin inhibitor (Kunitz) family. Based on the analysis of expression patterns, Solyc09g084480.2, Solyc03g020080.2, Solyc03g098760.1, and Solyc01g009020.1 were identified as key genes in the defense system of S. lycopersicum. The major endopeptidase genes such as Tabs008250, Tabs007396, and Tabs005701 in the larval stages of T. absoluta were also detected as potential targets of the plant endopeptidase inhibitors. The interaction mode between these endopeptidase and endopeptidase inhibitors was predicted based on the protein structure construction. This study aims to reveal the molecular response of S. lycopersicum to feeding by T. absoluta with high throughput sequencing and bioinformatics analysis.

The tomato leafminer (Tuta absoluta) is a highly destructive global quarantine pest. The methoprene-tolerant (Met) protein, a member of the bHLH/PAS family of transcription factors, forms complexes with other family members to transduce the juvenile hormone signal, which regulates insect growth and development. However, the functions of the TaMet gene have rarely been studied in T. absoluta. Herein, we investigated the significance of TaMet in T. absoluta. Spatiotemporal expression analysis revealed that TaMet exhibited comparable expression patterns in males and females, with high expression levels during the early pupal and early adult stages. TaMet was predominantly expressed in the female ovary and male wing. TaMet knockdown impaired ovarian development in female adults, causing irregular arrangement and increased spacing of the egg epithelial cells in the ovary. Silencing TaMet also led to a 67.25% reduction in female spawning and a 67.21% decrease in the offspring hatching rate. Furthermore, the vitellogenin content was significantly diminished, and the expression levels of vitellogenin (Vg) and vitellogenin receptor (VgR) genes were significantly downregulated. In contrast, silencing TaMet in 3-day-old male pupae resulted in an 80% mortality rate and various phenotypic abnormalities, including body melanism, molting defects, and wing deformities. Moreover, the expression levels of wing development and chitin metabolism genes decreased significantly after knocking down TaMet. Our results indicate that TaMet plays a significant dual role in male molting and female reproduction of T. absoluta.