Juvenile hormone (JH) signaling plays an important role in regulation of reproductive diapause in insects. However, we have little understanding of the effect of JH on gene expression at the transcriptome level in diapause. Galeruca daurica is a new pest in the Inner Mongolia grasslands with obligatory summer diapause in the adult stage. Topical application of a JH analog methoprene at the pre-diapause stage delayed the adults entering diapause and inhibited lipid accumulation whereas it did not during diapause. Using Illumina sequencing technology and bioinformatics tools, 54 and 138 differentially expressed genes (DEGs) were detected at 1 and 2 d after treatment, respectively. The KEGG analysis showed that the DEGs were mainly enriched in the metabolism pathways. qRT-PCR analysis indicated that methoprene promoted the expression of genes encoding vitellogenin, fork head transcription factor and Krüppel homolog 1, whereas suppressed the expression of genes encoding juvenile hormone-binding protein, juvenile hormone esterase, juvenile hormone acid methyltransferase, juvenile hormone epoxide hydrolase and fatty acid synthase 2. These results indicate that JH signaling plays an important role in regulating reproductive diapause of G. daurica.

The high-density-dependent phase change from solitary to gregarious individuals in locusts is a typical example of phenotypic plasticity. However, the underlying molecular mechanism is not clear. In this study, first, Oedaleus asiaticus were treated with high-density population stress and then analyzed by Illumina sequencing on days 1, 3, 5, and 7 of the body color change to identify the stage-specific differentially expressed genes (DEGs). The KEGG pathway enrichment analysis of the identified DEGs revealed their role in metabolic pathways. Furthermore, the expression patterns of the nine key DEGs were studied in detail; this showed that the material change in locusts began on the third day of the high-density treatment, with the number of DEGs being the largest, indicating the importance of this period in the phase transition. In addition, the phenotypic change involved several key genes of important regulatory pathways, possibly working in a complex network. Phenotypic plasticity in locusts is multifactorial, involving multilevel material network interactions. This study improves the mechanistic understanding of phenotypic variation in insects at the genetic level.

MicroRNAs (miRNAs) function as vital regulators of diapause in insects through their ability to post-transcriptionally suppress target gene expression. In this study, the miRNA of Ostrinia furnacalis, an economically important global crop pest species, was characterized. For the included analyses, 9 small RNA libraries were constructed using O. furnacalis larvae in different diapause states (non-diapause, ND; diapause, D; diapause-termination, DT). The results identified 583 total miRNAs, of which 256 had previously been identified, whereas 327 were novel. Furthermore, comparison analysis revealed that 119 and 27 miRNAs were differentially expressed in the D vs. ND and DT vs. D, respectively. Moreover, the expression patterns of their miRNAs were also analyzed. GO and KEGG analysis of the target genes of differentially expressed miRNAs highlighted the importance of these miRNAs as diapause regulators in O. furnacalis, especially through metabolic processes, endocrine processes, 20-hydroxyecdysone, and circadian clock signaling pathways. In summary, this study highlighted the involvement of specific miRNAs in the control of diapause in O. furnacalis. To the best of our knowledge, this is the first study to identify miRNA expression patterns in O. furnacalis, thereby providing reference and novel evidence enhancing our current understanding of how small RNAs influence insect diapause.

In order to determine the specific genes and proteins that are affected by matrine and play a role in regulating metabolism in the locust species Oedaleus asiaticus, we conducted RNA-seq, proteomic sequencing, and bioinformatics analyses on third-instar nymphs. These nymphs were divided into two groups: one group was grown under normal conditions, while the other group was treated with matrine. The purpose of this investigation was to gain insight into the molecular mechanisms underlying matrine resistance. Genes and proteins that exhibited differential expression were identified and subjected to analysis using bioinformatics software. The DESeq analysis revealed a total of 743 transcripts that were differentially expressed (DETs). Among these, 208 transcripts were up-regulated, and 535 were downregulated in ZO/ZCK. The iTRAQ discovered that 34 and 65 proteins were, respectively, up- and down-regulated in ZO/ZCK. Additionally, enrichment studies based on Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed. The KEGG and GO analysis of the DEGs suggested the essential roles of matrine treatment in the regulation of O. asiaticus, especially via the biosynthesis of amino acids, glycolysis/gluconeogenesis, iInsulin signaling pathway and MAPK signaling pathway. The findings demonstrated that matrine exerted control of the growth of O. asiaticus via modulating the synthesis of metabolism and biosynthesis. Increased expression of detoxifying enzymes was observed, which may be related to matrine detoxification. These findings provide a basis for better comprehension of the molecular mechanism behind the regulation of development mediated by matrine in Asian locust hoppers.

Prothoracicotropic hormone (PTTH) is a secretory neuropeptide initiating insect metamorphosis via ecdysteroid synthesis. While the PTTH–ecdysone axis is well-established in development, its specific role in diapause regulation and the underlying mechanisms in agricultural pests like Ostrinia furnacalis are less understood. To address this, we identified O. furnacalis’ PTTH gene (OfPTTH) and investigated its spatiotemporal expression and function using RNAi and 20-hydroxyecdysone (20E) rescue assays. Our findings show that OfPTTH expression was lowest during diapause, significantly increasing upon its termination, and exhibiting an extended developmental periodicity during diapause. OfPTTH-silencing was associated with reduced expression of ecdysone-signaling genes, leading to broad physiological disruptions including altered ecdysone and juvenile hormone signaling, inhibited insulin/IGF signaling, suppressed lipid metabolic reprogramming (triglyceride accumulation), and decreased heat shock protein expression. These events ultimately caused larval diapause-like developmental arrest, pupation failure, and mortality. Exogenous 20E treatment promoted pupation in OfPTTH-knockdown larvae and restored the expression of several downstream ecdysone-signaling genes, suggesting that impaired 20E signaling contributes to the observed developmental abnormalities. This study supports an important role of the PTTH–20E axis in O. furnacalis development and diapause-associated regulation and provides a basis for further evaluation of OfPTTH as a potential target for RNAi-based pest management.