Detection of QTL with effects on osmoregulation capacities in the rainbow trout (Oncorhynchus mykiss)

Abstract

BackgroundThere is increasing evidence that the ability to adapt to seawater in teleost fish is modulated by genetic factors. Most studies have involved the comparison of species or strains and little is known about the genetic architecture of the trait. To address this question, we searched for QTL affecting osmoregulation capacities after transfer to saline water in a nonmigratory captive-bred population of rainbow trout.ResultsA QTL design (5 full-sib families, about 200 F2 progeny each) was produced from a cross between F0 grand-parents previously selected during two generations for a high or a low cortisol response after a standardized confinement stress. When fish were about 18 months old (near 204 g body weight), individual progeny were submitted to two successive hyper-osmotic challenges (30 ppt salinity) 14 days apart. Plasma chloride and sodium concentrations were recorded 24 h after each transfer. After the second challenge, fish were sacrificed and a gill index (weight of total gill arches corrected for body weight) was recorded. The genome scan was performed with 196 microsatellites and 85 SNP markers. Unitrait and multiple-trait QTL analyses were carried out on the whole dataset (5 families) through interval mapping methods with the QTLMap software. For post-challenge plasma ion concentrations, significant QTL (P < 0.05) were found on six different linkage groups and highly suggestive ones (P < 0.10) on two additional linkage groups. Most QTL affected concentrations of both chloride and sodium during both challenges, but some were specific to either chloride (2 QTL) or sodium (1 QTL) concentrations. Six QTL (4 significant, 2 suggestive) affecting gill index were discovered. Two were specific to the trait, while the others were also identified as QTL for post-challenge ion concentrations. Altogether, allelic effects were consistent for QTL affecting chloride and sodium concentrations but inconsistent for QTL affecting ion concentrations and gill morphology. There was no systematic lineage effect (grand-parental origin of QTL alleles) on the recorded traits.ConclusionsFor the first time, genomic loci associated with effects on major physiological components of osmotic adaptation to seawater in a nonmigratory fish were revealed. The results pave the way for further deciphering of the complex regulatory mechanisms underlying seawater adaptation and genes involved in osmoregulatory physiology in rainbow trout and other euryhaline fishes.

Rapid parallel evolution of standing variation in a single, complex, genomic region is associated with life history in steelhead/rainbow trout

“…Our results provide data from natural populations in California and Oregon that support prior studies on diverse O. mykiss lineages using candidate genes, genome wide association and QTL mapping to explore the genetic architecture of traits associated with life history in O. mykiss, including migration [17,32,42,46,48,[65][66][67][68][69][70][71][72][73][74][75][76]. Many of these studies have identified QTL or significant associations between markers on Omy5 and life-history traits such as spawn timing [47,65,68], smoltification [42,46] and development rate or early maturation [17,66,67,70].…”

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…Washington and Idaho; Le Bras et al 2011 Genomic regions linked to embryonic development and breeding timing under differential selection between resident and anadromous individuals.…”

Transcriptomics of salinity tolerance capacity in Arctic charr (Salvelinus alpinus): a comparison of gene expression profiles between divergent QTL genotypes

“…This is likely due to the wide diversity and suitability of fishes for transfer experiments, as movement between high and low salinities is an essential part of the ontogeny and reproductive cycle of many species (43). Quantitative trait locus (QTL) studies on Arctic charr (Salvelinus alpinus) (47), Atlantic salmon (Salmo salar) (48), and rainbow trout (Oncorhynchus mykiss) (31) show that intraspecific variation in osmoregulatory capacity amid hyperosmotic conditions (i.e., hypo-osmoregulation) is shaped, in part, by allelic variation. However, QTL experiments involving nonmodel organisms such as these typically suffer from drawbacks that can impair QTL detection.…”