Comparative proteomics provides insights into diapause program of Bactrocera minax (Diptera: Tephritidae)

The transcriptome reveals the potential mechanism of 20E terminating diapause in cotton bollworm, Helicoverpa armigera

BACKGROUND

Diapause is a crucial adaptive strategy employed across numerous insect species, endowing them to survive in unfavorable environments. Helicoverpa armigera, one of the most destructive pests globally, undergoes diapause in the pupa stage, which is essential for its survival during the overwintering period and ultimately determines the following year's population density. 20E is a primary hormone that regulates the process of pupae diapause. However, a comprehensive analysis of the mechanisms by which 20E regulates the initiation and termination of diapause in H. armigera remains lacking.

RESULTS

In the present study, exogenous 20E was initially administered to diapausing pupae, and the results demonstrated that 20E markedly enhanced the development and eclosion rate of diapausing pupae, indicating that 20E treatment effectively terminated the diapause of H. armigera. Subsequently, RNA-Seq was employed to construct a comprehensive transcriptome map of the 20E-induced termination of diapause. The results demonstrated that there were 2836 differentially expressed genes, including 1315 genes that were upregulated and 1521 genes that were downregulated, in the 20E injection group relative to the control group. KEGG and GO enrichment analysis showed that these genes were associated with various metabolic pathways. Moreover, additional analysis revealed that the majority of the pivotal genes associated with metabolism (including glycolysis/gluconeogenesis, glycerolipid, amino sugar and nucleotide sugar metabolism), cell signaling pathways (such as insulin, Wnt, MAPK signaling pathways), the cell cycle, and stress resistance exhibited altered expression following 20E injection. These findings suggest that 20E exerts its primary influence on metabolic processes, cell signaling pathways, cell cycle, and stress resistance during the termination of diapause.

CONCLUSIONS

Our study presents a systematic and comprehensive analysis of the genes associated with 20E-induced diapause termination, thereby providing a foundation for elucidating the molecular mechanism of 20E regulating diapause. Furthermore, the findings lend support to the utilization of ecdysone analogs as pesticides in diapause-based pest management.

Transcriptional Regulatory Network of the Embryonic Diapause Termination Process in Artemia

Artemia is a typical animal used for the study of the diapause mechanism. The research on the regulation mechanism of diapause mainly focuses on the occurrence and maintenance of diapause. There are few studies on the mechanism of embryonic pause termination (EDT), especially for its transcriptional regulation mechanism. This study integrated transcriptional regulatory data from ATAC-seq and gene expression data from RNA-seq to explore the transcriptional regulatory mechanisms involved in the EDT process. Through integrated analysis, four important transcription factors (TFs), SVP, MYC, RXR, and SMAD6, were found to play a role in the EDT process, in which SVP, MYC, and RXR were upregulated, while SMAD6 was downregulated in the EDT stage. Through co-expression analysis, a transcription regulatory network for these four TFs was constructed and the functions of the TFs were analyzed. The expression of the TFs was further verified by RT-qPCR. Through functional analysis, SVP was found to be predominantly involved in cell adhesion and signal transduction. MYC probably played a role in protein binding. RXR may function in the process of RNA binding and the transfer of phosphorus-containing groups. Smad6 regulated the signal transduction, cell adhesion, and oxidation-reduction processes. The expression of the key TFs was verified by RT-qPCR. The results of this work provide important clues for the mechanism of transcriptional regulation in the EDT process of Artemia.

Integrating ATAC-Seq and RNA-Seq Reveals the Signal Regulation Involved in the Artemia Embryonic Reactivation Process

Embryonic diapause is a common evolutionary adaptation observed across a wide range of organisms. Artemia is one of the classic animal models for diapause research. The current studies of Artemia diapause mainly focus on the induction and maintenance of the embryonic diapause, with little research on the molecular regulatory mechanism of Artemia embryonic reactivation. The first 5 h after embryonic diapause breaking has been proved to be most important for embryonic reactivation in Artemia. In this work, two high-throughput sequencing methods, ATAC-seq and RNA-seq, were integrated to study the signal regulation process in embryonic reactivation of Artemia at 5 h after diapause breaking. Through the GO and KEGG enrichment analysis of the high-throughput datasets, it was showed that after 5 h of diapause breaking, the metabolism and regulation of Artemia cyst were quite active. Several signal transduction pathways were identified in the embryonic reactivation process, such as G-protein-coupled receptor (GPCR) signaling pathway, cell surface receptor signaling pathway, hormone-mediated signaling pathway, Wnt, Notch, mTOR signaling pathways, etc. It indicates that embryonic reactivation is a complex process regulated by multiple signaling pathways. With the further protein structure analysis and RT-qPCR verification, 11 GPCR genes were identified, in which 5 genes function in the embryonic reactivation stage and the other 6 genes contribute to the diapause stage. The results of this work reveal the signal transduction pathways and GPCRs involved in the embryonic reactivation process of Artemia cysts. These findings offer significant clues for in-depth research on the signal regulatory mechanisms of the embryonic reactivation process and valuable insights into the mechanism of animal embryonic diapause.

Metabolite Changes in Orange Dead Leaf Butterfly Kallima inachus during Ontogeny and Diapause

Holometabolism is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). The developmental change of whole body in metabolite levels of holometabolous insects are usually ignored and lack study. Diapause is an alternative life-history strategy that can occur during the egg, larval, pupal, and adult stages in holometabolous insects. Kallima inachus (Lepidoptera: Nymphalidae) is a holometabolous and adult diapausing butterfly. This study was intended to analyze metabolic changes in K. inachus during ontogeny and diapause through a non-targeted UPLC-MS/MS (ultra-performance liquid chromatograph coupled with tandem mass spectrometry) based metabolomics analysis. A variety of glycerophospholipids (11), amino acid and its derivatives (16), and fatty acyls (nine) are crucial to the stage development of K. inachus. 2-Keto-6-acetamidocaproate, N-phenylacetylglycine, Cinnabarinic acid, 2-(Formylamino) benzoic acid, L-histidine, L-glutamate, and L-glutamine play a potentially important role in transition of successive stages (larva to pupa and pupa to adult). We observed adjustments associated with active metabolism, including an accumulation of glycerophospholipids and carbohydrates and a degradation of lipids, as well as amino acid and its derivatives shifts, suggesting significantly changed in energy utilization and management when entering into adult diapause. Alpha-linolenic acid metabolism and ferroptosis were first found to be associated with diapause in adults through pathway analyses. Our study lays the foundation for a systematic study of the developmental mechanism of holometabolous insects and metabolic basis of adult diapause in butterflies.

Comparative transcriptome analysis of different developmental stage of Bactrocera minax (Diptera: Tephritidae): Implication of the molecular basis of its obligatory diapause induction

The Chinese citrus fruit fly, Bactrocera minax (Enderlein), a devastating pest in citrus, has an obligatory diapause at the pupal stage. Although the physiology of obligatory diapause has been well described, the molecular mechanisms underlying the process remain unknow. Here we investigated the molecular mechanisms of obligatory diapause induction in B. minax using high-throughput RNA-Seq data from second-instar larva (2L), third-instar larva (3L) and pupa (P) stages. A total of 116,402 unigenes were obtained, of which 54,781 unigenes were successfully annotated in public databases, and the differentially expressed genes in the 3L vs 2L, P vs 2L, and P vs 3L comparisons were identified. The cluster co-expression patterns of the differentially expressed genes revealed that significantly differentially-expressed genes in the pupal stage were predicted to be related to diapause induction. All differentially expressed genes were investigated by GO functional and KEGG pathway analysis, and the results showed that genes involved in processes such as 20-hydroxyecdysone (20E) biosynthesis, cell cycle and metabolic pathways are likely related to obligatory diapause induction in B. minax. These results provide important information on the transcriptome of the Chinese citrus fruit fly that can be used for further functional studies as well as contributing to our understanding of the molecular basis of obligatory diapause induction and suggesting potential molecular targets for the control of this pest.