Genome-wide association analysis of adaptation to oxygen stress in Nile tilapia (Oreochromis niloticus)

Abstract

Background Tilapia is one of the most abundant species in aquaculture. Hypoxia is known to depress growth rate, but the genetic mechanism by which this occurs is unknown. In this study, two groups consisting of 3140 fish that were raised in either aerated (normoxia) or non-aerated pond (nocturnal hypoxia). During grow out, fish were sampled five times to determine individual body weight (BW) gains. We applied a genome-wide association study to identify SNPs and genes associated with the hypoxic and normoxic environments in the 16th generation of a Genetically Improved Farmed Tilapia population. Results In the hypoxic environment, 36 SNPs associated with at least one of the five body weight measurements (BW1 till BW5), of which six, located between 19.48 Mb and 21.04 Mb on Linkage group (LG) 8, were significant for body weight in the early growth stage (BW1 to BW2). Further significant associations were found for BW in the later growth stage (BW3 to BW5), located on LG1 and LG8. Analysis of genes within the candidate genomic region suggested that MAPK and VEGF signalling were significantly involved in the later growth stage under the hypoxic environment. Well-known hypoxia-regulated genes such as igf1rb, rora, efna3 and aurk were also associated with growth in the later stage in the hypoxic environment. Conversely, 13 linkage groups containing 29 unique significant and suggestive SNPs were found across the whole growth period under the normoxic environment. A meta-analysis showed that 33 SNPs were significantly associated with BW across the two environments, indicating a shared effect independent of hypoxic or normoxic environment. Functional pathways were involved in nervous system development and organ growth in the early stage, and oocyte maturation in the later stage. Conclusions There are clear genotype-growth associations in both normoxic and hypoxic environments, although genome architecture involved changed over the growing period, indicating a transition in metabolism along the way. The involvement of pathways important in hypoxia especially at the later growth stage indicates a genotype-by-environment interaction, in which MAPK and VEGF signalling are important components.

Non-synonymous variation and protein structure of candidate genes associated with selection in farm and wild populations of turbot (Scophthalmus maximus)

“…An i gf1rb polymorphism was reported to be associated with growth traits in the freshwater goby Odontobutis potamophila 100 , and divergence and polymorphism analysis of igf1ra and igf1rb in the orange-spotted grouper ( Epinephelus coioides ) suggested their importance in growth regulation and breeding of this species 101 . Moreover, the involvement of igf1rb in growth during hypoxia was recently reported in a genome-wide association analysis of adaptation to oxygen stress in farmed Nile tilapia ( Oreochromis niloticus ) 102 . Our study revealed a very strong differentiation of the polymorphic HbαD subunit when comparing wild vs farm populations.…”

Fipronil impairs the GABAergic brain responses of Nile Tilapia during the transition from normoxia to acute hypoxia

“…Most of these response processes happen very early at the onset of hypoxia through the activation of pathways depending on already present proteins (Michiels, 2004). Besides that, these adaptive responses to hypoxia depend on a complex regulation that leads to differential expressions of genes and neurotransmitter signaling that changes according to tissue, fish species, and hypoxia condition dependent (Lunde et al, 2011; Solaini et al, 2010; Soto‐Arape et al, 1995; Yu et al, 2021). Studies in the past decades pointed to an essential role of the hypoxia‐inducible factors (HIF) in mammals for gene expression regulation during hypoxia (Majmundar et al, 2010).…”

Chromosome-level genome sequence of the Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus) highlights regions of introgression with O. mossambicus

“…To further develop the GIFT strain and to enable future improvements, several studies have been investigating the genetic bases underlying traits of economic interest. As a consequence, Quantitative Trait Loci (QTL) associated with sex determination [11], Tilapia Lake Virus resistance [12, 13], feed efficiency [14], adaptation to oxygen stress [15] in the GIFT strain have now been identified.…”