Vitellogenin regulates estrogen-related receptor expression by crosstalk with the JH and IIS-TOR signaling pathway in Polyrhachis vicina Roger (Hymenoptera, Formicidae)

Sex- and caste-specific developmental responses to juvenile hormone in an ant with maternal caste determination

Juvenile hormone is considered to be a master regulator of polyphenism in social insects. In the ant Cardiocondyla obscurior, whether a female egg develops into a queen or a worker is determined maternally and caste-specific differentiation occurs in embryos, so that queens and workers can be distinguished in a non-invasive manner from late embryogenesis onwards. This ant also exhibits two male morphs - winged and wingless males. Here, we used topical treatment with juvenile hormone III and its synthetic analogue methoprene, a method that influences caste determination and differentiation in some ant species, to investigate whether hormone manipulation affects the development and growth of male, queen- and worker-destined embryos and larvae. We found no effect of hormone treatment on female caste ratios or body sizes in any of the treated stages, even though individuals reacted to heightened hormone availability with increased expression of krüppel-homolog 1, a conserved JH first-response gene. In contrast, hormone treatment resulted in the emergence of significantly larger males, although male morph fate was not affected. These results show that in C. obscurior, maternal caste determination leads to irreversible and highly canalized caste-specific development and growth.

Estrogen-related receptor, a molecular target against lepidoptera pests

Until recently, chemical pesticides were one of the most effective means of controlling agricultural pests; therefore, the search for insecticide targets for agricultural pests has been an ongoing problem. Estrogen-related receptors (ERRs) are transcription factors that regulate cellular metabolism and energy homeostasis in animals. Silkworms are highly sensitive to chemical pesticides, making them ideal models for pesticide screening and evaluation. In this study, we detected ERR expression in key organs involved in pesticide metabolism in silkworms (Bombyx mori), including the fat body and midgut. Using ChIP-seq technology, many estrogen- related response elements were identified in the 2000-bp promoter region upstream of metabolism-related genes, almost all of which were potential ERR target genes. The ERR inhibitor, XCT-790, and the endocrine disruptor, bisphenol A, significantly inhibited expression of the ERR target genes, BmTreh-1, BmTret-1, BmPK, BmPFK, and BmHK, in the fat bodies of silkworms, resulting in pupation difficulties in silkworm larvae that ultimately lead to death. In addition, based on the clarification that the ERR can bind to XCT-790, as observed through biofilm interferometry, its three-dimensional spatial structure was predicted, and using molecular docking techniques, small-molecule compounds with a stronger affinity for the ERR were identified. In summary, utilizing the powerful metabolic regulatory function of ERR in Lepidoptera pests, the developed small molecule inhibitors of ERR can be used for future control of Lepidoptera pests.

Ecdysone-controlled nuclear receptor ERR regulates metabolic homeostasis in the disease vector mosquito Aedes aegypti

Hematophagous mosquitoes require vertebrate blood for their reproductive cycles, making them effective vectors for transmitting dangerous human diseases. Thus, high-intensity metabolism is needed to support reproductive events of female mosquitoes. However, the regulatory mechanism linking metabolism and reproduction in mosquitoes remains largely unclear. In this study, we found that the expression of estrogen-related receptor (ERR), a nuclear receptor, is activated by the direct binding of 20-hydroxyecdysone (20E) and ecdysone receptor (EcR) to the ecdysone response element (EcRE) in the ERR promoter region during the gonadotropic cycle of Aedes aegypti (named AaERR). RNA interference (RNAi) of AaERR in female mosquitoes led to delayed development of ovaries. mRNA abundance of genes encoding key enzymes involved in carbohydrate metabolism (CM)-glucose-6-phosphate isomerase (GPI) and pyruvate kinase (PYK)-was significantly decreased in AaERR knockdown mosquitoes, while the levels of metabolites, such as glycogen, glucose, and trehalose, were elevated. The expression of fatty acid synthase (FAS) was notably downregulated, and lipid accumulation was reduced in response to AaERR depletion. Dual luciferase reporter assays and electrophoretic mobility shift assays (EMSA) determined that AaERR directly activated the expression of metabolic genes, such as GPI, PYK, and FAS, by binding to the corresponding AaERR-responsive motif in the promoter region of these genes. Our results have revealed an important role of AaERR in the regulation of metabolism during mosquito reproduction and offer a novel target for mosquito control.

Genome-Wide Identification of Vitellogenin Gene Family and Comparative Analysis of Their Involvement in Ovarian Maturation in Exopalaemon carinicauda

Vitellogenin (Vtg) is a precursor of yolk proteins in egg-laying vertebrates and invertebrates and plays an important role in vitellogenesis and embryonic development. However, the Vtg family remains poorly characterized in Exopalaemon carinicauda, a major commercial mariculture species found along the coasts of the Yellow and Bohai Seas. In this study, 10 Vtg genes from the genomes of E. carinicauda were identified and characterized. Phylogenetic analyses showed that the Vtg genes in crustaceans could be classified into four groups: Astacidea, Brachyra, Penaeidae, and Palaemonidae. EcVtg genes were unevenly distributed on the chromosomes of E. carinicauda, and a molecular evolutionary analysis showed that the EcVtg genes were primarily constrained by purifying selection during evolution. All putative EcVtg proteins were characterized by the presence of three conserved functional domains: a lipoprotein N-terminal domain (LPD_N), a domain of unknown function (DUF1943), and a von Willebrand factor type D domain (vWD). All EcVtg genes exhibited higher expression in the female hepatopancreas than in other tissues, and EcVtg gene expression during ovarian development suggested that the hepatopancreas is the main synthesis site in E. carinicauda. EcVtg1a, EcVtg2, and EcVtg3 play major roles in exogenous vitellogenesis, and EcVtg3 also plays a major role in endogenous vitellogenesis. Bilateral ablation of the eyestalk significantly upregulates EcVtg mRNA expression in the female hepatopancreas, indicating that the X-organ/sinus gland complex plays an important role in ovarian development, mostly by inducing Vtg synthesis. These results could improve our understanding of the function of multiple Vtg genes in crustaceans and aid future studies on the function of EcVtg genes during ovarian development in E. carinicauda.

A Study on the Effect of Energy on the Development of Silkworm Embryos Using an Estrogen-Related Receptor

Energy metabolism is a fundamental process in all organisms. During silkworm (Bombyx mori) embryonic development, there is a high demand for energy due to continuous cell proliferation and differentiation. Estrogen-related receptors (ERRs) are transcriptional regulatory factors that play crucial roles in mammalian energy storage and expenditure. Although most insects have one ERR gene, it also participates in the regulation of energy metabolism, including carbohydrate metabolism in Drosophila, Aphid, and Silkworm. However, no study has reported the direct impact of energy metabolism on embryonic development in silkworms. In this study, we used transgenic technology to increase silkworm (B. mori; Bm) BmERR expression during embryonic development and explored the impact of energy on embryonic development. We found no significant change in the quality of silkworm eggs compared to that of wild-type silkworms. However, there was an increase in the consumption of vitellin, a major nutrient in embryos. This resulted in a decrease in glucose content and a significant increase in ATP content. These findings provide evidence that the acceleration of energy metabolism promotes embryonic development and enhances the motility of hatched silkworms. In addition, these results provide a novel perspective on the relationship between energy metabolism and embryonic development in other insects.

Worker Reproduction and Caste Polymorphism Impact Genome Evolution and Social Genes Across the Ants

Eusocial insects are characterized by several traits, including reproductive division of labor and caste polymorphisms, which likely modulate genome evolution. Concomitantly, evolution may act on specific genes and pathways underlying these novel, sociality-associated phenotypes. Reproductive division of labor should increase the magnitude of genetic drift and reduce the efficacy of selection by reducing effective population size. Caste polymorphism has been associated with relaxed selection and may facilitate directional selection on caste-specific genes. Here, we use comparative analyses of 22 ant genomes to test how reproductive division of labor and worker polymorphism influence positive selection and selection intensity across the genome. Our results demonstrate that worker reproductive capacity is associated with a reduction in the degree of relaxed selection but is not associated with any significant change to positive selection. We find decreases in positive selection in species with polymorphic workers, but no increase in the degree of relaxed selection. Finally, we explore evolutionary patterns in specific candidate genes associated with our focal traits in eusocial insects. Two oocyte patterning genes previously implicated in worker sterility evolve under intensified selection in species with reproductive workers. Behavioral caste genes generally experience relaxed selection associated with worker polymorphism, whereas vestigial and spalt, both associated with soldier development in Pheidole ants, experience intensified selection in worker polymorphic species. These findings expand our understanding of the genetic mechanisms underlying elaborations of sociality. The impacts of reproductive division of labor and caste polymorphisms on specific genes illuminate those genes' roles in generating complex eusocial phenotypes.

IPS (In-Plant System) Delivery of Double-Stranded Vitellogenin and Vitellogenin receptor via Hydroponics for Pest Control in Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

Diaphorina citri, a vector of citrus huanglongbing (HLB) disease, frequently leads to HLB outbreaks and reduces Rutaceae crop production. Recent studies have investigated the effects of RNA interference (RNAi) targeting the Vitellogenin (Vg4) and Vitellogenin receptor (VgR) genes, which are involved in egg formation in this pest, providing a theoretical foundation for developing new strategies to manage D. citri populations. This study presents RNAi methods for Vg4 and VgR gene expression interference and reveals that dsVgR is more effective than dsVg4 against D. citri. We demonstrated that dsVg4 and dsVgR persisted for 3-6 days in Murraya odorifera shoots when delivered via the in-plant system (IPS) and effectively interfered with Vg4 and VgR gene expression. Following Vg4 and VgR gene expression interference, egg length and width in the interference group were significantly smaller than those in the negative control group during the 10-30-day development stages. Additionally, the proportion of mature ovarian eggs in the interference group was significantly lower than that in the negative control group at the 10, 15, 20, 25, and 30-day developmental stages. DsVgR notably suppresses oviposition in D. citri, with fecundity decreasing by 60-70%. These results provide a theoretical basis for controlling D. citri using RNAi to mitigate the spread of HLB disease.

Nilaparvata lugens ERR2 regulates moulting and ovary development is related to hormone signalling

The nuclear receptor (NR) superfamily is one of the largest groups of transcription factors in living organisms. Oestrogen related receptor (ERR) is a class of nuclear receptors closely related to oestrogen receptors (ERs). In this study, the Nilaparvata lugens (N. lugens) ERR2 (NlERR2) was cloned, and the expression of NlERR2 was detected by qRT-PCR to explore the distribution of NlERR2 during development and in different tissues. Using RNAi and qRT-PCR, the interaction between NlERR2 and related genes of the 20-hydroxyecdysone (20E) and juvenile hormone (JH) signalling pathways was studied. The results showed that topical application of 20E and juvenile hormone III (JHIII) affected the expression of NlERR2, and NlERR2 could affect the expression of genes related to 20E and JH signalling pathways. Furthermore, NlERR2 and JH/20E hormone signalling-related genes affect moulting and ovarian development. NlERR2 and NlE93/NlKr-h1 affect the transcriptional expression of Vg-related genes. In summary, NlERR2 is related to hormone signalling pathways, which is also related to the expression of Vg and Vg related genes. Brown planthopper is one of the most important rice pests. This study provides an important basis for mining new targets for pest control.