Insulin-like growth factors (IGFs) play crucial roles in the regulation of animal growth and reproduction. However, the functional and regulatory mechanisms underlying ovarian growth and oocyte maturation in teleosts remain unclear. In this study, the expression profiles of lncRNAs and mRNAs were analyzed in the ovaries of golden pompano (Trachinotus ovatus) treated with IGF1 and IGF2 proteins to gain insights into the role of these two IGF ligands in the regulation of ovarian development and maturation. A total of 1494 lncRNAs and 8728 mRNAs were differentially expressed following IGF1 treatment compared with the control group. A total of 101 lncRNAs and 377 mRNAs were differentially expressed after IGF2 treatment compared to those in the control group. The results revealed that KEGG pathways enriched by target genes of the DE lncRNAs overlapped significantly with those enriched by the DE mRNAs in both the IGF1 and IGF2 groups. The key overlapping enriched pathways included ECM receptor interaction, gap junction, Hedgehog signaling pathway, Ras signaling pathway, Rap1 signaling pathway, TGF beta signaling pathway, Wnt signaling pathway, GnRH signaling pathway, progesterone-mediated oocyte maturation, oocyte meiosis, cell cycle, and MAPK signaling pathway. The differentially expressed genes (DEGs) involved in ovarian development and oocyte maturation were cyp17a1, cyp19a1, star, hsd17b3, hsd17b7, adam23, slc26a6, htr2b, h2ax, nanos3, krt18, pgr, and inhbb, following IGF1 and IGF2 treatment. Furthermore, four lncRNAs (MSTRG.66521.1, MSTRG.49969.1, MSTRG.59923.1, and MSTRG.13767.1) for IGF1 and two (MSTRG.20896.2 and MSTRG.58123.2) for IGF2 within the lncRNA–mRNA network were found to target DEGs related to ovarian development and maturation. This suggests that IGFs may affect reproductive processes by regulating the expression of lncRNAs and mRNAs. RT-qPCR analysis revealed that these six lncRNAs showed high expression levels in the brain, pituitary, liver, and gonad tissues, indicating their potential involvement in regulating ovarian growth and development. This study elucidates the lncRNA–mRNA regulatory mechanism in response to IGF1 and IGF2 treatment during stage III of ovarian development in golden pompano, thereby deepening our understanding of its functional role.

Aurantiochytrium sp. has received much attention as a potential resource for mass production of omega-3 fatty acids, which contribute to improved growth and reproduction in aquatic animals. In this study, we evaluated the gonadal index changes in zebrafish supplemented with 1–3% Aurantiochytrium sp. crude extract (TE) and the effects of ex vivo environmental Aurantiochytrium sp. on oocytes. 1% TE group showed significant improvement in the gonadal index, and both in vitro incubation and intraperitoneal injection promoted the maturation of zebrafish oocytes. In contrast, the transcriptome revealed 576 genes that were differentially expressed between the 1% TE group and the control group, including 456 up-regulated genes and 120 down-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway analysis of differentially expressed genes indicated that Aurantiochytrium sp. potentially affects pathways such as lipid metabolism, immune regulation, and oocyte development in zebrafish. The results of this study enriched the knowledge of Aurantiochytrium sp. in regulating gonadal development in zebrafish and provided a theoretical basis for its application in aquaculture.

Insulin-like growth factors (IGFs) are hormones that primarily stimulate and regulate animal physiological processes. In this study, we cloned and identified the open reading frame (ORF) cDNA sequences of IGF family genes: the insulin-like growth factor 1 (IGF1), insulin-like growth factor 2 (IGF2), and insulin-like growth factor 3 (IGF3). We found that IGF1, IGF2, and IGF3 have a total length of 558, 648, and 585 base pairs (bp), which encoded a predicted protein with 185, 215, and 194 amino acids (aa), respectively. Multiple sequences and phylogenetic tree analysis showed that the mature golden pompano IGFs had been conserved and showed high similarities with other teleosts. The tissue distribution experiment showed that IGF1 and IGF2 mRNA levels were highly expressed in the liver of female and male fish. In contrast, IGF3 was highly expressed in the gonads and livers of male and female fish, suggesting a high influence on fish reproduction. The effect of fasting showed that IGF1 and mRNA expression had no significant difference in the liver but significantly decreased after long-term (7 days) fasting in the muscles and started to recover after refeeding. IGF2 mRNA expression showed no significant difference in the liver but had a significant difference in muscles for short-term (2 days) and long-term fasting, which started to recover after refeeding, suggesting muscles are more susceptible to both short-term and long-term fasting. In vitro incubation of 17β-estradiol (E₂) was observed to decrease the IGF1 and IGF3 mRNA expression level in a dose- (0.1, 1, and 10 μM) and time- (3, 6, and 12 h) dependent manner. In addition, E₂ had no effect on IGF2 mRNA expression levels in a time- and dose-dependent manner. The effect of 17α-methyltestosterone (MT) in vitro incubation was observed to significantly increase the IGF3 mRNA expression level in a time- and dose-dependent manner. MT had no effect on IGF2 mRNA but was observed to decrease the IGF1 mRNA expression in the liver. Taken together, these data indicate that E₂ and MT may either increase or decrease IGF expression in fish; this study provides basic knowledge and understanding of the expression and regulation of IGF family genes in relation to the nutritional status, somatic growth, and reproductive endocrinology of golden pompano for aquaculture development.

The marine protist Aurantiochytrium produces several bioactive chemicals, including EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), and other critical fish fatty acids. It has the potential to improve growth and fatty acid profiles in aquatic taxa. This study evaluated zebrafish growth performance in response to diets containing 1% to 3% Aurantiochytrium sp. crude extract (TE) and single extract for 56 days. Growth performance was best in the 1% TE group, and therefore, this concentration was used for further analyses of the influence of Aurantiochytrium sp. Levels of hepatic lipase, glucose-6-phosphate dehydrogenase, acetyl-CoA oxidase, glutathione peroxidase, and superoxide dismutase increased significantly in response to 1% TE, while malic enzyme activity, carnitine lipid acylase, acetyl-CoA carboxylase, fatty acid synthase, and malondialdehyde levels decreased. These findings suggest that Aurantiochytrium sp. extract can modulate lipase activity, improve lipid synthesis, and decrease oxidative damage caused by lipid peroxidation. Transcriptome analysis revealed 310 genes that were differentially expressed between the 1% TE group and the control group, including 185 up-regulated genes and 125 down-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway analyses of the differentially expressed genes revealed that Aurantiochytrium sp. extracts may influence liver metabolism, cell proliferation, motility, and signal transduction in zebrafish.

Aromatase inhibitor letrozole (LZ) and 17α-methyltestosterone (MT) are commonly used for sex control breeding to induce female-to-male sex reversal in aquaculture. However, studies on the molecular regulatory mechanisms of LZ and MT are still limited. Here, a comparative transcriptome analysis was conducted on the hypothalamus, the gonad, and the liver of golden pompano (Trachinotus ovatus) after 30 days of LZ and MT treatment, which demonstrated significant sexual size dimorphism. Following LZ treatment, the transcriptome data identified 156, 890, and 1286 different expression genes (DEGs) in the hypothalamus, the liver, and the gonad, respectively. After MT treatment, the transcriptome data identified 114, 876, and 950 DEGs in the hypothalamus, the liver, and the gonad, respectively. Functional enrichment analysis revealed that DEGs were involved in oocyte meiosis and steroid-hormone synthesis following LZ treatment. Similarly, the analysis indicated that DEGs were associated with cysteine and methionine metabolism and steroid-hormone synthesis after MT treatment. Further analysis showed that LZ treatment can promote the first meiotic division but inhibit the second meiotic division of the oocyte. MT treatment promotes polyamine synthesis to induce oocyte apoptosis, both of which affect the trajectory of ovarian differentiation in golden pompano. However, LZ and MT have converse effects in sex hormone synthesis. LZ inhibits estrogen metabolism but promotes cholesterol synthesis by regulating sqle, cyp3a40, ugt1a1, and ugt2a1, while MT promotes estrogen metabolism but inhibits the conversion of cholesterol to pregnenolone by regulating cyp19a1, cyp1a, and hsd17b7. This study reveals that both LZ and MT may inhibit the ovarian differentiation and induce masculinization through different regulatory mechanisms, which provides a fundamental insight into the sex control breeding in aquaculture.