Identification of reproduction-related genes and pathways in the Culter alburnus H-P-G axis and characterization of their expression differences in malformed and normal gynogenetic ovaries

Dietary arginine regulates the growth performance, antioxidant capacity, and immune response in Culter alburnus

Culter alburnus is sensitive to stressors. Arginine is a precursor of nitric oxide, which can effectively relieve the level of oxidative stress and improve the antioxidant and immune capacity of fish. The effect of different arginine levels on topmouth culter (Culter alburnus) fry development performance, liver antioxidant capacity, and immune parameters were investigated in this study. Five diets (1.96%, ARG1, control group; 2.28%, ARG2; 2.52%, ARG3; 2.81%, ARG4; 3.09%, ARG5) were used to feed fry (initial weight 0.31 ± 0.01 g) for 8 weeks. The data showed that the final weight (FW), weight gain rate (WGR), and specific growth rate (SGR) of the ARG3 and ARG4 groups were significantly improved, while the feed conversion ratio (FCR) reduced significantly. Compared with the ARG1 group, all groups remarkably reduced the crude ash content of the whole body. The activity of hepatic superoxide dismutase (SOD) and the content of hepatic glutathione (GSH) were significantly increased in the ARG3 and ARG4 groups, while the malondialdehyde (MDA) content was significantly decreased. Compared with the ARG1 group, arginine levels in ARG2, ARG3, and ARG4 groups up-regulated the expression levels of Nrf2, down-regulated the gene expression level of Keap1 in the liver. And the expression of Nrf2/Keap1 pathway downstream genes Mn-SOD and CAT was up-regulated in ARG2 and ARG3 groups. Furthermore, the expression levels of MyD88 and IL-1β were down-regulated, and the anti-inflammatory gene TGF-β expression levels were up-regulated in the ARG2, ARG3, and ARG4 groups. Additionally, compared to the ARG1 group, there was a significant increase in the relative expression levels of the C3 and C4 genes in the ARG4 group. In conclusion, 2.28-2.81% dietary arginine levels improved the growth performance, promoted antioxidant capacity, and enhance immune response. The optimal level of arginine was determined by the quadratic regression analysis of SGR and FCR to be 2.55% of diet (5.43% of dietary protein) and 2.53% of diet (5.38% of dietary protein), accordingly.

Comparative transcriptome analysis of gonads in male and female Pseudobagrus ussuriensis (Bagridae, Siluriformes)

As an important aquaculture fish in the Heilongjiang River Basin, Pseudobagrus ussuriensis has high economic value, and all-male culture is beneficial to the economic development of this fish. In this study, the transcriptomes of gonads in males and females were analyzed, and some genes related to gonad development were found. A total of 82,931 unigenes were found (average length 1504 bp, N50 1829 bp). In addition, 4689 differentially expressed genes (DEGs; including 1424 genes upregulated and 3265 genes downregulated in males) were identified. Some genes associated with testis development (such as Dmrt1 and Ropn1l) were significantly upregulated in males, while genes related to ovary development (such as Wnt2, PLC, Cyp19a, ZP3) were significantly downregulated in males, demonstrating that these genes have a crucial influence on gonad development in P. ussuriensis. Some signaling pathways related to gonad development were found, such as the Wnt pathway and oocyte meiosis. The results of RNA-seq obtained in this study provide theoretical data for elucidating the potential mechanism of gonad development of P. ussuriensis and reliable genomic data for the establishment of mono-sex breeding of P. ussuriensis.

Analysis of reproduction-related transcriptomes on pineal-hypothalamic-pituitary-ovarian tissues during estrus and anestrus in Tan sheep

Seasonal estrus is an important factor limiting the fertility of some animals such as sheep. Promoting estrus in the anestrus season is one of the major ways in improving the fecundity of seasonally breeding animals. The pineal-hypothalamus-pituitary-ovary (PHPO) axis plays a decisive role in regulating animal reproduction. However, the molecular mechanisms by which the PHPO axis regulates seasonal reproduction in animals are not well understood, especially in Tan sheep. To this end, we collected pineal, hypothalamus, pituitary and ovary tissues from Tan sheep during estrus and anestrus for RNA-Sequencing, and performed bioinformatics analysis on the entire regulatory axis of the pineal-hypothalamic-pituitary-ovary (PHPO). The results showed that 940, 1,638, 750, and 971 DEGs (differentially expressed genes, DEGs) were identified in pineal, hypothalamus, pituitary and ovary, respectively. GO analysis showed that DEGs from PHPO axis-related tissues were mainly enriched in "biological processes" such as transmembrane transport, peptide and amide biosynthesis and DNA synthesis. Meanwhile, KEGG enrichment analysis showed that the bile acid secretion pathway and the neuroactive ligand-receptor interaction pathway were significantly enriched. Additionally, four potential candidate genes related to seasonal reproduction (VEGFA, CDC20, ASPM, and PLCG2) were identified by gene expression profiling and protein-protein interaction (PPI) analysis. These findings will contribute to be better understanding of seasonal reproduction regulation in Tan sheep and will serve as a useful reference for molecular breeding of high fertility Tan sheep.