Adaptive evolution of low salinity tolerance and hypoosmotic regulation in a euryhaline teleost, Takifugu obscurus

Abstract

Background The mechanism of osmoregulation is crucial for maintaining growth, development, and life activities in teleosts. Takifugu obscurus, the only euryhaline species in the genus Takifugu, is a proper model organism for studying the mechanism of low salt-tolerance and hypoosmotic regulation.Results In this study, whole genome sequencing data were obtained from 90 pufferfish representing five species within this genus, T. rubripes, T. obscurus, T. flavidus, T. niphobles, and T. bimaculatus. Using a phylogeny, PCA, and population structure analyses, we observed similar amounts of population genetic differentiation among species. The five species are closely related to each other and have differentiated within a relatively short period, while T. bimaculatus and T. flavidus shared the most similar genetic backgrounds. We further identified hundreds of genes under selection related to hypoosmotic regulation between T. obscurus and other Takifugu species, including 16 representative genes involving ion transporters ( atp1a3 , atp2a2 , atp2a3 , slc13a1 , slc5a8 , slc12a2 , slc12a4 , slc26a2 , scn1b , and kcna 2/3/10), genes involved in hormone regulation ( fyn , prlr , and grb2 ), and a gene associated with water absorption ( aqp3 ). Conclusions: Our findings provide preliminary insight into the mechanism of osmoregulation and will facilitate follow-up validation of candidate genes related to osmoregulation in T. obscurus .

Transcriptome Profiling Reveals a Divergent Adaptive Response to Hyper- and Hypo-Salinity in the Yellow Drum, Nibea albiflora

“…Ion transporters and the permeability of the plasma membrane are of great significance to the osmotic regulation mechanism of euryhaline fish [ 46 , 47 ]. This study focused on several traditional ion transporters and channels.…”

Genome-Scale Phylogenetic and Population Genetic Studies Provide Insight Into Introgression and Adaptive Evolution of Takifugu Species in East Asia

“…In the past two decades, with the success of artificial breeding of Tb and Tf, the aquaculture industry has rapidly developed around the coast of the China East Sea and Yellow Sea ( Zhou Z. et al, 2019 ). In particular, Tf is widely cultured in the central and northern Taiwan Straits, and the northern border of artificial Tb breeding grounds is in the Bohai Sea, which is not its traditional habitat ( Zhang et al, 2020 ). In addition, breeding programs of Tb and Tf also involve their hybridization ( Jiang et al, 2016 ).…”

“…However, only a few studies involving phylogenetic and interspecific hybridization analysis in Takifugu species exist and are based on the mitochondrial genome and amplified fragment length polymorphisms (AFLP) ( Yamanoue et al, 2009 ; Takahashi et al, 2017 ). In addition, there are only a few population genetic studies involving multiple Takifugu species to date ( Zhang et al, 2020 ). The publication of high-quality genomes motivates population genetics and comparative genomic studies, which are crucial to the understanding of phylogenetic relationships, evolutionary histories, and adaptation strategies of the different Takifugu species during explosive speciation ( Nielsen et al, 2009 ).…”