MUSCLE TRANSCRIPTOME CHANGES WITHIN ONE GENERATION OF NILE TILAPIA DOMESTICATION

Domestication of fish species is a relatively recent practice compared to plants and terrestrial mammals, which have been domesticated for over ten thousand years . Nile tilapia (Oreochromis niloticus ) is one of the most widely farmed fish species in the world, with a production of 4.2 million tonnes in 2016 (FAO). One of the most important breeding programs was the genetically improved farmed tilapia (GIFT) project that was established in 1988 with the aim of selecting individuals for advantageous traits . Phenotypes such as  improved  muscle growth are inherited from one generation to the next and are primarily linked to specific mutations and allele shifts across the genome. However, adaptation occurs from the very first generation of domestication. To  investigate whether the number of generations and the level of domestication are accompanied with gradual changes in gene expression levels, we compared the muscle transcriptome of wild Nile tilapia progenitors (W) and their first generation under captivity offspring (D). Remarkably, we identified substantial gene expression changes in the muscle within the first generation of domestication. Out of 2121 differentially expressed genes (Fig. 1), 2015 were found to be upregulated in wild fish . Many of those genes are expressed in immune cells that are primarily found in the spleen. These indications pinpoint a plausible immune cell infiltration in the muscle of the wild fish due to chronic inflammation and exposure to pathogens such as parasites, bacteria and viruses. On the contrary, 106 genes were upregulated in the offspring and were associated with metabolism and muscle-specific functions, such as muscle system process and striated muscle tissue development.

Acknowledgement : This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no 683210) and from the Research Council of Norway under the Toppforsk programme (grant agreement no 250548/F20).