Mating behaviors in ovoviviparous black rockfish (Sebastes schlegelii): molecular function of prostaglandin E2 as both a hormone and pheromone.

Prostaglandins (PGs) are profound hormones in teleost sexual behavior, especially in mating. PGs act as pheromones that affect the olfactory sensory neurons of males, inducing the initiation of a series of mating behaviors. However, the molecular mechanism by which PGs trigger mating behavior in ovoviviparous teleosts is still unclear. In the present study, we employed the ovoviviparous black rockfish (Sebastes schlegelii), an economically important marine species whose reproductive production is limited by incomplete fertilization, as a model species. The results showed that when the dose of PGE2 was higher than 10 nmol/L, a significant (P < 0.05) increase in mating behaviors was observed. Dual-fluorescence in situ hybridization indicated that PGE2 could fire specific neurons in different brain regions and receptor cells in the olfactory sac. After combining with specific neurons in the central nervous system (CNS), a series of genes related to reproduction are activated. The intracerebroventricular administration of PGE2 significantly increased lhb levels (P < 0.05) in both sexes. Moreover, steroidogenesis in gonads was also affected, inducing an increase (P < 0.05) in E2 levels in males and T levels in females. PGE2 levels were also increased significantly (P < 0.05) in both sexes. The present study revealed that PGE2 can activate mating behavior in black rockfish in both hormone and pheromone pathways, leading to variations in sex steroid levels and activation of reproductive behaviors. Our results provide not only novel insight into the onset of mating behaviors in ovoviviparous teleosts but also solutions for the incomplete fertilization caused by natural mating in cage aquaculture. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00214-w.

Pro-inflammatory cytokine IL1ß1 participates in promoting parturition related pathways in the ovoviviparous teleost black rockfish (Sebastes schlegelii).

Along with the evolution process, the reproductive strategies evolved including oviparity, viviparity and ovoviviparity, to fit the residential environment maximize the survival rate of the off spring. In mammals, the key to the initiation of parturition is the inflammatory response at the maternal-fetal interface. As a pro-inflammatory cytokine, interleukin 1 beta (IL1ß) plays an important role in the process of human parturition. While less is known about IL1ß1 in teleost parturition, identification of the functions of IL1ß1 in inducing the parturition, black rockfish, an ovoviviparity teleost, which provides over 60% nutrition supply for over 50 000 embryos though a placenta like structure during pregnant, was employed as the research model. In the present study, based on the gene cloning, we detected the expression pattern of both Il1b1 and its receptor perinatal period, as well as the localization to the ovary by in situ hybridization. The different expression genes in transcriptomic data of perinatal primary ovarian cells treated with the recombinant IL1ß1 (rIL1ß1) obtained by prokaryotic expression system were analyzed. Differentially expressed genes, functional enrichment and pathway analysis mainly included immune response, signal transduction and cell death. In summary, our research provides novel insights into the potential role of IL1ß1 in the parturition of ovoviviparity teleost.

Ultraviolet-ozone concomitantly induced MoS2/MoOx heterostructures with improved SERS performance.

Surface-enhanced Raman scattering (SERS) is a non-destructive spectral analysis technique. It has the virtues of high detectivity and sensitivity, which have been extensively studied for low-trace molecule detection. In the choices of SERS substrate materials, low-cost and abundant reserved transition metal oxide/chalcogenide materials have been regarded as promising substitutes for noble metals; however, their inferior SERS enhancement severely limits their practical application. Herein, a class of MoS2/MoOx heterostructures have been demonstrated with significantly improved SERS performance. Experimentally, MoS2/MoOx heterostructures were prepared by precisely controlled oxidation of MoS2 nanospheres in an ultraviolet-ozone environment, and the optimal SERS substrate was obtained with 14 hours of ultraviolet-ozone irradiation. SERS measurements revealed superior SERS performance with a detection limit of 10-7 M (rhodamine 6G) and an enhancement factor of 7.477 × 106 (R6G@10-7 M) could be obtained. Finally, the intuitive SERS enhancement mechanism was investigated via energy band analysis. It revealed that the constructed heterostructures enhanced the electron-hole separation, and the electrons were successively transferred to the analytes and significantly promoted the molecular polarizability, improving the SERS performance.

Olfactory receptor OR52N2 for PGE2 in mediation of guppy courtship behaviors.

Prostaglandins (PGs) are a type of physiologically active unsaturated fatty acids. As an important sex pheromone, PGs play a vital role in regulating the reproductive behaviors of species by mediating nerve and endocrine responses. In this study, guppy (Poecilia reticulate) was used as the model specie to detect the function of PGE2 in inducing the onset of courtship behaviors. Our results showed that adding PGE2 into the water environment could activate the courtship behavior of male guppy, indicating that the peripheral olfactory system mediated the PGE2 function. Thereafter, the open reading frame (ORF) of olfactory receptor or52n2 was cloned, which was 936 bp in length, coding 311 amino acids. As a typical G protein-coupled receptor, OR52N2 had a conservative seven α-helix transmembrane domains. To confirm the regulatory relationship between OR52N2 and PGE2, dual-luciferase reporter assay was employed to verify the activation of downstream CREB signaling pathways. Results showed that PGE2 significantly enhanced CRE promoter activity in or52n2 ORF transient transfected HEK-293 T cells. Finally, localization of or52n2 mRNA were observed in ciliated receptor cells of the olfactory epithelium using in situ hybridization. Our results provide a novel insight into sex pheromone signaling transduction in reproductive behavior.

Function of secretoneurin in regulating the expression of reproduction-related genes in ovoviviparous black rockfish (Sebastes schlegelii).

Secretoneurin (SN), a conserved peptide derived from secretogranin-2 (scg2), also known as secretogranin II or chromogranin C, plays an important role in regulating gonadotropin in the pituitary, which affects the reproductive system. This study aimed to clarify the mode of action of scg2 in regulating gonad development and maturation and the expression of mating behavior-related genes. Two scg2 cDNAs were cloned from the ovoviviparity teleost black rockfish (Sebastes schlegelii). In situ hybridization detected positive scg2 mRNA signals in the telencephalon and hypothalamus, where sgnrh and kisspeptin neurons were reported to be located and potentially regulated by scg2. In vivo, intracerebral ventricular injections of synthetic black rockfish SNa affected brain cgnrh, sgnrh, kisspeptin1, pituitary lh and fsh and gonad steroidogenesis-related gene expression levels with sex dimorphism. In vitro, a similar effect was found in primary cultured brain and pituitary cells. Thus, SN could contribute to the regulation of gonadal development, as well as reproductive behaviors, including mating and parturition.

Comparative transcriptomic analysis and genome-wide characterization of the Semaphorin family reveal the potential mechanism of angiogenesis around embryo in ovoviviparous black rockfish (Sebastes schlegelii).

To guarantee the quality and survival rate of their offspring, ovoviviparous teleost evolved special characteristics of in vivo fertilization and embryo development. Maternal black rockfish, having over 50 thousand embryos developing within the ovary simultaneously, provided around 40% nutrition throughout oocyte development, while the capillaries around each embryo contributed the rest 60% during pregnancy. Since fertilization, capillaries started to proliferate and developed into a placenta-like structure that covered over half of each embryo. Aimed to characterize the potential mechanism behind, comparative transcriptome analysis of samples collected according to the process of pregnancy. Three important time point in the process, including mature oocyte stage, fertilization and sarcomere period, were chosen for the transcriptome sequencing. Our study identified key pathways and genes involved in the cell cycle as well as DNA replication and repair, cell migration and adhesion, immune, and metabolic functions. Notably, several of the semaphoring gene family members were differently expressed. To confirm the accuracy of these genes, total of 32 sema genes were identified from the whole genome and distinct expression pattern of sema genes was observed in different pregnant stages. Our results revealed a novel insight for further investigating the functions of sema genes in reproduction physiology and embryo processes in ovoviviparous teleost.

Molecular characterization and expression patterns of glucocorticoid receptors in the viviparous black rockfish Sebastes schlegelii.

Glucocorticoid receptors (GRs) are ligand-activated transcription factors associated with anti-inflammation, stress, metabolism and gonadal development. In this study, two gr genes (gr1 and gr2) were cloned and analyzed from a viviparous teleost, black rockfish (Sebastes schlegelii). The phylogenetic analysis of GRs showed that GR1 and GR2 clustered into teleost GR1 and GR2 separately and differed from the GRs of tetrapods or basal ray-finned fishes. Black rockfish GRs possess four modular domains of the nuclear receptor superfamily: an N-terminal domain (NTD), a DNA-binding domain (DBD), a hinge region (HR) and a ligand-binding domain (LBD). Nine conserved amino acid inserts were found in the GR1 DBD, and the ligand cavity-related amino acids of GR1 and GR2 LBD were slightly different. Tissue distribution analysis revealed that grs was widely expressed in various tissues, while cyp11b was mainly expressed in the testis and head kidney. The cyp11b transcripts were localized in the interrenal glands of the head kidney, the main source of cortisol; grs transcripts were detected in oocytes, the follicle layer and the ovarian wall. Histologically, significant blood vessel dilation was observed in the fetal membrane during or after parturition of black rockfish. The highest levels of serum cortisol and ovarian cyp11b mRNA were detected in parturition. In addition, the relative expression level of gr1 was upregulated significantly after delivery, while the levels of gr2 showed no significant change. In addition, in vitro GC treatment inhibited the expression of il1b but significantly upregulated the transcription of il1r1. These data provide evidence that GRs are likely to work as anti-inflammatory factors by inhibiting the functions of pro-inflammatory factors in the parturition of black rockfish.

Molybdenum Oxide/Tungsten Oxide Nano-heterojunction with Improved Surface-Enhanced Raman Scattering Performance.

By virtue of their high uniformity and stability, metal oxide-based surface-enhanced Raman spectroscopy (SERS) substrates have attracted enormous attention for molecular trace detection. However, strategies for further enhancing the SERS sensitivity are still desired. Herein, MoOx/WOx nano-heterojunctions are constructed by mixing MoOx and WOx together (MoOx/WOx hybrid) with diverse weight ratios. Using a 532 nm laser as the excitation source and R6G as the Raman reporter, it is shown that the Raman signal intensity (for the peak @ 1360 cm-1) obtained on the optimal MoOx/WOx hybrid (MoOx/WOx = 1:1/3) is twice that observed on a pure MoOx or WOx substrate. Moreover, a limit of detection of 10-8 M and an enhancement factor of 108 are achieved. In the SERS enhancement mechanism investigation, it is revealed that MoOx and WOx form a staggered band structure. During the SERS measurement, electron-hole pairs are generated in the nano-heterojunction using the incident laser. They are then separated by the built-in potential with the electrons moving toward WOx. The accumulated electrons on WOx are further transferred to the R6G molecules through the coupling of orbitals. Consequently, the molecular polarizability is amplified, and SERS performance is enhanced. The abovementioned explanation is supported by the evidence that the contribution of the chemical enhancement mechanism in the optimal MoOx/WOx hybrid substrate is about 2.5 times or 5.9 times that in the pure WOx or MoOx substrate.