Transcriptome characterization of BPG axis and expression profiles of ovarian steroidogenesis-related genes in the Japanese sardine

MicroRNAs are involved in ovarian physiology of greater amberjack (Seriola dumerili) under captivity

Gonad maturation is critical for the reproductive success of any organism, and in fish, captivity can significantly affect their reproductive performance, leading to maturation incompetence and spawning failure. The greater amberjack (Seriola dumerili), a fish species recently introduced to aquaculture fails to undergo oocyte maturation, ovulation, and spawning when reared in aquaculture facilities. Since confinement has been shown to influence gonad maturation and completion of the reproductive cycle, investigations into epigenetic mechanisms may shed light on the reasoning behind the reproductive dysfunctions of fish under captivity. Among the known important epigenetic regulators are small non-coding RNAs (sncRNAs), and in particular microRNAs (miRNAs). In this study, immature, maturing (late vitellogenesis), and spent ovaries of captive greater amberjack were collected, and the differential expression of miRNAs in the three different ovarian development stages was examined. Expression patterns of conserved and novel miRNAs were identified, and potential targets of highly differentially expressed miRNAs were detected. Additionally, read length distribution showed two prominent peaks in the three different ovarian maturation stages, corresponding to miRNAs and putative piwi-interacting RNAs (piRNAs), another type of ncRNAs with a germ-cell specific role. Furthermore, miRNA expression patterns and their putative target mRNAs are discussed, in relevance with the different ovarian maturation stages of captive greater amberjack. Overall, this study provides insights into the role of miRNAs in the reproductive dysfunctions observed in fish under captivity and highlights the importance of epigenetic mechanisms in understanding and managing the reproductive performance of economically important fish species.

Assessing reproductive effects and epigenetic responses in Austrolebias charrua exposed to Roundup Transorb®: Insights from miRNA profiling and molecular interaction analysis

This study examines the effects of Roundup Transorb® (RDT) exposure on reproductive functions and ovarian miRNA expression in Austrolebias charrua. Exposure to RDT (at 0.065 or 5 mg. L-1 for 96 h) significantly disrupts fertility, evidenced by changes in fertilization rates and egg diameter. Profiling of ovarian miRNAs identified a total 205 miRNAs in A. charrua. Among these, three miRNAs were upregulated (miR-10b-5p, miR-132-3p, miR-100-5p), while ten miRNAs were downregulated (miR-499-5p, miR-375, miR-205-5p, miR-206-3p, miR-203a-3p, miR-133b-3p, miR-203b-5p, miR-184, miR-133a-3p, miR-2188-5p) compared to non-exposed fish. This study reveals that differentially expressed miRNAs are linked to molecular pathways such as steroid hormone biosynthesis, lipid and carbohydrate metabolism, bioenergetics, and antioxidant defense. It also analyzes molecular interactions between miRNAs and target genes during RDT exposure in annual killifish, providing insights into biomarkers in ecotoxicology. Moreover, it provides scope for developing environmental health assessment models based on epigenomic endpoints, supporting the protection of biodiversity and ecosystem services through the quantification of stress responses in living organisms exposed to pesticides.

Effect of different temperature variations on the physiological state of catfish species: a systematic review

Catfish are a highly diverse group of fish that are found in various regions across the globe. The significance of catfish culture extends to various aspects, including food security, economic advancement, preservation of cultural legacy, and ecological stewardship. The catfish industry is presently encountering unprecedented challenges as a consequence of the variability in water temperature caused by climate change. Temperature is a significant abiotic component that regulates and restricts fish physiology throughout their life cycle. The impact of severe temperatures on various species of catfish is dependent upon the magnitude of the stressor and additional influencing factors. This paper presents an analysis of the effects of temperature fluctuations on various aspects of catfish species, including growth and survival, blood parameters, enzymatic and hormone response, oxygen consumption rates, sound generation and hearing skills, nutritional requirements, and other phenotypic attributes. While this review is certainly not exhaustive, it offers a broad synopsis of the ideal temperature ranges that are most favorable for several catfish species. In-depth research to investigate the interacting impacts of severe temperature occurrences in conjunction with other associated environmental stresses on a wider variety of catfish species is crucial in order to further our understanding of how catfish species will respond to the anticipated climate change in the future.

Phenotypic sorting of individual male and female intersex Cherax quadricarinatus and analysis of molecular differences in the gonadal transcriptome

Cherax quadricarinatus exhibit sexual dimorphism, with males outpacing females in size specification and growth rate. However, there is limited understanding of the molecular mechanisms underlying sex determination and sex differentiation in crustaceans. To study the differences between intersex individuals and normal individuals, this study counted the proportion of intersex individuals in the natural population, collected the proportion of 7 different phenotypes in 200 intersex individuals, and observed the differences in tissue sections. RNA-seq was used to study the different changes in the transcriptome of normal and intersex gonads. The results showed that: the percentage of intersex in the natural population was 1.5 %, and the percentage of different types of intersex ranged from 0.5 % to 22.5 %; the sections revealed that the development of normal ovaries was stagnant at the primary oocyte stage when intersex individuals with ovaries were present; We screened for pathways and genes that may be associated with gonadal development and sex, including ovarian steroid synthesis, estrogen signaling pathway, oocyte meiosis, progesterone-mediated oocyte maturation, etc. Relevant genes including tra2a, dmrta2, ccnb2, foxl2, and smad4. This study provides an important molecular basis for sex determination, sex-controlled breeding, and unisex breeding in red crayfish.

Characterization of eight types of 17β-hydroxysteroid dehydrogenases from the Japanese sardine Sardinops melanostictus: The probable role of type 12a in ovarian estradiol synthesis

17β-hydroxysteroid dehydrogenases (Hsd17bs) play a critical role in sex steroid biosynthesis. Although multiple types of Hsd17b have been found in fish, there is limited research on their expression and function. Recently, we succeeded in identifying eight types of Hsd17b (types 3, 4, 7, 8, 10, 12a, 12b, and 14) by RNA sequencing in the Japanese sardine Sardinops melanostictus, a commercially important clupeoid fish; however, a homologous sequence of Hsd17b1, which catalyzes the key reaction of estradiol-17β (E2) synthesis, was absent. Here, we aimed to identify the Hsd17b type that plays a major role in E2 synthesis during ovarian development in Japanese sardine. The cDNAs encoding those eight types of Hsd17b were cloned and sequenced. The expressions of hsd17b3, hsd17b12a, and hsd17b12b were higher in ovary than in testis. In particular, hsd17b12a was predominantly expressed in the ovary. Expression of hsd17b3, hsd17b4, hsd17b12a, and hsd17b12b in the ovary increased during ovarian development. The enzymatic activities of Hsd17b3, Hsd17b12a, and Hsd17b12b were evaluated by expressing their recombinants in human embryonic kidney 293T cells. Hsd17b12a and Hsd17b12b catalyzed the conversion of androstenedione (AD) to testosterone (T) and estrone (E1) to E2. The results of in vitro bioassays using sardine ovaries indicated that E2 is synthesized from pregnenolone via AD and T, but not E1. These results suggest that Hsd17b12a plays a major role in E2 synthesis in sardine ovary by catalyzing the conversion of AD to T.

Comparative gonad transcriptome analysis in cobia (Rachycentron canadum)

Background: Cobia (Rachycentron canadum) is a species of fish with high commercial potential particularly due to fast growth rates. The evidence of sexual size dimorphism favoring females indicate potential benefits in having a monosex culture. However, the involvement of genetic factors responsible for sexual development and gonadal maintenance that produces phenotypic sex in cobia is largely unknown. Methods: In the present study, we performed transcriptome sequencing of cobia to identify sex-biased significantly differentially expressed genes (DEGs) in testes and ovaries. The reliability of the gonad transcriptome data was validated by qPCR analysis of eight selected significantly differential expressed sex-related candidate genes. Results: This comparative gonad transcriptomic analysis revealed that 7,120 and 4,628 DEGs are up-regulated in testes or ovaries, respectively. Further functional annotation analyses identified 76 important candidate genes involved in sex determination cascades or sex differentiation, including 42 known testis-biased DEGs (dmrt1, amh and sox9 etc.), and 34 known ovary-biased DEGs (foxl2, sox3 and cyp19a etc.). Moreover, eleven significantly enriched pathways functionally related to sex determination and sex differentiation were identified, including Wnt signaling pathway, oocyte meiosis, the TGF-beta signaling pathway and MAPK signaling pathway. Conclusion: This work represents the first comparative gonad transcriptome study in cobia. The putative sex-associated DEGs and pathways provide an important molecular basis for further investigation of cobia's sex determination, gonadal development as well as potential control breeding of monosex female populations for a possible aquaculture setting.

Differential expression profiles of microRNAs in musk gland of unmated and mated forest musk deer (Moschus berezovskii)

Background

The formation of musk is a complex biophysical and biochemical process that change with the rut of male forest musk deer. We have reported that the mating status of male forest musk deer might result to the variations of chemical composition and microbiota of musk and its yields. Critical roles for microRNAs (miRNAs) of multi-tissues were profiled in our previous study; however, the role for miRNAs of the musk gland remains unclear in this species.

Methods

In this study, we used Illumina deep sequencing technology to sequence the small RNA transcriptome of unmated male (UM) and mated male (UM) of Chinese forest musk deer.

Results

We identified 1,652 known miRNAs and 45 novel miRNAs, of which there were 174 differentially expressed miRNAs between UM and MM. chi-miR-21-5p, ipu-miR-99b and bta-miR-26a were up-regulated in UM among the 10 most differentially expressed miRNAs. Functional enrichment of the target genes showed that monosaccharide biosynthetic process, protein targeting, cellular protein catabolic process enriched higher in MM. Meanwhile, structural molecule activity, secretion by cell, regulated exocytosis and circulatory system process enriched more in UM, hinting that the formation of musk in UM was mediated by target genes related to exocytosis. The miRNA-mRNA pairs such as miR-21: CHD7, miR143: HSD17B7, miR-141/200a: Noc2 might involve in musk gland development and musk secretion, which need to be verified in future study.