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By favoring certain characteristics of interest in breeding, domestication is accompanied by a loss of overall genetic diversity. By identifying the selection signatures shared by four more or less domesticated populations of rainbow trout, researchers at the GABI unit sought to identify genome regions linked to ancient evolutionary processes that are essential to species survival.

They analyzed the genome of 176 trout from French and North American populations, using a high-density genotyping chip recently developed by the unit (665,000 markers). Working with several domesticated populations of different origins, we have been able to free ourselves from the individual history of these populations, and instead focus on what is shared by the whole. 

In all, 9 regions under positive selection were identified, containing 253 genes, 17 of which had already been detected in other vertebrate species (from fish to mammals). More surprisingly, 4 regions, comprising 29 genes, are maintained in heterozygous state in all populations despite the domestication process underway since the end of the 19th century. The genes identified in these heterozygous regions are involved in functions essential to the survival of the species, such as cell organization, embryonic development and immunity.

In conclusion, the analysis of genetic diversity within a recently domesticated species has revealed a large number of genes of interest, as well as the singular dynamics of diversity, with in particular the maintenance of regions "resistant" to homozygosity, the determinism and effects of which remain to be clarified.

Contact :

• Florence PHOCAS, GABI, INRAE, Jouy-en-Josas