Detection Of QTL and functional genomics study of osmoregulation capacities in the rainbow trout (Oncorhynchus mykiss)

Euryhalin teleosts can live in freshwater as well as in seawater. The success of their survival depends then on their osmotic acclimation capacities. The objective of my work is to describe acclimation processes in the salted water at the rainbow trout by a study coupling functional genomic and genetic approaches. From a first differential gill transcriptomic study, a list of candidates genes was established. This study also allowed to investigate the physiological answer to a hyperosmotic kinetics challenge. Main results reveal good euryhalinity capacities of the tested trouts and a maximum trasncriptomic answer 24 h after the seawater transfer. Biological processes involved in the acclimation mechanisms are also proposed. A second part of this work consisted of the characterisation of the genetic control of processes linked to seawater acclimation in rainbow trout. Using as characters, a two times repeated 24h post seawater transfer plasma sodium and chloride levels, as well as gill weight, unitrait and multitrait analyses allowed to reveal 18 QTL among whom 9 are qualified as robust. A last approach of eQTL detection then allowed, based on a gill transcriptomic analysis and on the results of the first two approaches, to offer 69 exclusive candidates genes. If the majority of these genes are offered as acting at functional level, some are suggested as positional candidates. It is the first time that a blending transcriptomie differential approach coupled to a QTL / eQTL study is led to a non-sequenced genome aquacole interest teleost for the acclimation capacity to different osmotic environments. The existence of a genetic element having an influence on the capacities of osmoregulation in teleost is shown here. These results lay the road with cobblestones for a definite investigation of the genetic bases of seawater acclimation processes in teleosts.