Project description:Owing to the demand for sustainable sex-control protocols in aquaculture, research in tilapia sex determination is gaining momentum. The mutual influence of environmental and genetic factors hampers disentangling the complex sex determination mechanism in Nile tilapia (Oreochromis niloticus). Previous linkage analyses have demonstrated quantitative trait loci for the phenotypic sex on linkage groups 1, 3, and 23. Quantitative trait loci for temperature-dependent sex reversal similarly reside on linkage group 23. The anti-Müllerian hormone gene (amh), located in this genomic region, is important for sexual fate in higher vertebrates, and shows sexually dimorphic expression in Nile tilapia. Therefore this study aimed at detecting allelic variants and marker-sex associations in the amh gene. Sequencing identified six allelic variants. A significant effect on the phenotypic sex for SNP ss831884014 (p<0.0017) was found by stepwise logistic regression. The remaining variants were not significantly associated. Functional annotation of SNP ss831884014 revealed a non-synonymous amino acid substitution in the amh protein. Consequently, a fluorescence resonance energy transfer (FRET) based genotyping assay was developed and validated with a representative sample of fish. A logistic linear model confirmed a highly significant effect of the treatment and genotype on the phenotypic sex, but not for the interaction term (treatment: p<0.0001; genotype: p<0.0025). An additive genetic model proved a linear allele substitution effect of 12% in individuals from controls and groups treated at high temperature, respectively. Moreover, the effect of the genotype on the male proportion was significantly higher in groups treated at high temperature, giving 31% more males on average of the three genotypes. In addition, the groups treated at high temperature showed a positive dominance deviation (+11.4% males). In summary, marker-assisted selection for amh variant ss831884014 seems to be highly beneficial to increase the male proportion in Nile tilapia, especially when applying temperature-induced sex reversal.

Project description:In this study, RNA-Seq was used to reveal the differences of molecular pathways in hepatopancreas of O. niloticus adapated to water with salinity of 8 or 16 practical salinity (psu), respectively, with fish at freshwater as the control,. Significantly changed pathways were mainly related to lipid metabolism, glucose utilization, protein consumption, osmotic regulation, signal transduction and immunology. Based on the tendencies from freshwater to 8 or 16 psu, the differentially expressed gene unions were categorized into eight unique models, which were further classified into three categories which were constant-change (either keep increasing or decreasing), change-then-stable and stable-then-change. In constant-change category, steroid biosynthesis, steroid hormone biosynthesis, fat digestion and absorption, complement and coagulation cascades were extremely significantly affected by ambient salinity (P < 0.01), indicating that these pathways play pivotal roles in molecular response to salinity acclimation from freshwater to saline water in O. niloticus, and should be the main research focus in the future. In change-then-stable category, ribosome, oxidative phosphorylation, peroxisome proliferator-activated receptors (PPAR) signaling pathway, fat digestion and absorption changed significantly with ambient increasing salinity (P < 0.01), showing these pathways were sensitive to environmental salinity variation, but had a response threshold, and would stop changing once salinity exceeds the threshold. In stable-then-change category, protein export, protein processing in endoplasmic reticulum, tight junction, thyroid hormone synthesis, antigen processing and presentation, glycolysis/gluconeogenesis and glycosaminoglycan biosynthesis - keratan sulfate were the top changed pathways (P < 0.01), suggesting that these pathways were not sensitive to salinity variation, but these pathways will respond significantly under salinity exceeding a certain level. The pathways and genes reported in this study laid on a solid foundation for future studies in understanding the underlying mechanism for salinity adaptation of freshwater fish. Examination of 3 different salinities treated hepatopancreas in Nile tilapia

Project description:In this study, RNA-Seq was used to reveal the differences of molecular pathways in hepatopancreas of O. niloticus adapated to water with salinity of 8 or 16 practical salinity (psu), respectively, with fish at freshwater as the control,. Significantly changed pathways were mainly related to lipid metabolism, glucose utilization, protein consumption, osmotic regulation, signal transduction and immunology. Based on the tendencies from freshwater to 8 or 16 psu, the differentially expressed gene unions were categorized into eight unique models, which were further classified into three categories which were constant-change (either keep increasing or decreasing), change-then-stable and stable-then-change. In constant-change category, steroid biosynthesis, steroid hormone biosynthesis, fat digestion and absorption, complement and coagulation cascades were extremely significantly affected by ambient salinity (P < 0.01), indicating that these pathways play pivotal roles in molecular response to salinity acclimation from freshwater to saline water in O. niloticus, and should be the main research focus in the future. In change-then-stable category, ribosome, oxidative phosphorylation, peroxisome proliferator-activated receptors (PPAR) signaling pathway, fat digestion and absorption changed significantly with ambient increasing salinity (P < 0.01), showing these pathways were sensitive to environmental salinity variation, but had a response threshold, and would stop changing once salinity exceeds the threshold. In stable-then-change category, protein export, protein processing in endoplasmic reticulum, tight junction, thyroid hormone synthesis, antigen processing and presentation, glycolysis/gluconeogenesis and glycosaminoglycan biosynthesis - keratan sulfate were the top changed pathways (P < 0.01), suggesting that these pathways were not sensitive to salinity variation, but these pathways will respond significantly under salinity exceeding a certain level. The pathways and genes reported in this study laid on a solid foundation for future studies in understanding the underlying mechanism for salinity adaptation of freshwater fish.

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Sex, salinity and sampling period dependent patterns of growth hormone mRNA expression in Mozambique tilapia.

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