Transcriptome Analysis Reveals Common and Differential Response to Low Temperature Exposure Between Tolerant and Sensitive Blue Tilapia (Oreochromis aureus)

Tilapias are very important to the world's aquaculture. As befitting fish of their tropical origin, their distribution, and culture practices are highly affected by low temperatures. In this study, we used genetic and genomic methodologies to reveal pathways involved in the response and tolerance of blue tilapia (Oreochromis aureus) to low temperature stress. Cold tolerance was characterized in 66 families of blue tilapia. Fish from cold-tolerant and cold-sensitive families were sampled at 24 and 12°C, and the transcriptional responses to low-temperature exposure were measured in the gills and liver by high-throughput mRNA sequencing. Four hundred and ninety four genes displayed a similar temperature-dependent expression in both tolerant and sensitive fish and in the two tissues, representing the core molecular response to low temperature exposure. KEGG pathway analysis of these genes revealed down-regulation of focal-adhesion and other cell-extracellular matrix (ECM) interactions, and up-regulation of proteasome and various intra-cellular proteolytic activities. Differential responses between cold-tolerant and cold-sensitive fish were found with genes and pathways that were up-regulated in one group and down-regulated in the other. This reverse response was characterized by genes involved in metabolic pathways such as glycolysis/gluconeogenesis in the gills and biosynthesis of amino-acids in the liver, with low temperature down-regulation in tolerant fish and up-regulation in sensitive fish

Effects of the acclimation to high salinity on intestinal ion and peptide transporters in two tilapia species that differ in their salinity tolerance

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Association between polymorphism in the Prolactin I promoter and growth of tilapia in saline-water

Tilapias are a group of species with a variable tolerance to high salinity, which are cultured worldwide in fresh, brackish and seawater. Prolactin I (PRL I) is known as a key hormone in osmoregulatory physiological pathways. A previous study, conducted in a single family, reported on association between polymorphism in a repetitive element within the promoter of the PRL I gene and growth rate of tilapia in saline water. This study was aiming to further validate this association in a larger sample size, and was conducted in nine families over two consecutive breeding seasons. We have confirmed this association in the three F2 families of Oreochromis mossambicus × Oreochromis niloticus hybrids challenged in the first year. The same pattern of improved growth for genotypes with shorter alleles originating from the O. niloticus grand-parental fish, although O. mossambicus is considered to be a more salt tolerant species, was demonstrated. The effects accounted for 13–15% of the phenotypic variance for growth rate (P < 0.05). In the six families from the second spawning season there was no association between the gene polymorphism and the fish growth in saline water. No association was evident between the polymorphism in the PRL I promoter and the expression of the gene