Variation in gene expression along a salinity gradient in wild populations of the euryhaline black‐chinned tilapia Sarotherodon melanotheron

Abstract

This study evaluated variation in expression of 11 genes within and among six wild populations of the black-chinned tilapia Sarotherodon melanotheron distributed along a salinity gradient from 0 to 100. Previous laboratory studies had shown that expression of these genes was sensitive to water salinity; the current study confirmed that a number of them also varied in expression in wild populations along the salinity gradient. Principal component analysis (PCA) first distinguished two, not mutually exclusive, sets of genes: trade-off genes that were highly expressed at one or other extreme of the salinity gradient and stress genes that were up-regulated at the two salinity extremes (i.e. a U-shaped expression pattern). The PCA clearly partitioned the populations into three groups based on their gene expression patterns and their position along the salinity gradient: a freshwater (GL; 0) population, four brackish and seawater (GB, HB, SM, SF; ranging from 20 to 50) populations and a hypersaline (SK, 100) population. Individual variation in gene expression was significantly greater within the populations at the extreme compared to intermediate salinities. These results reveal phenotypically plastic regulation of gene expression in S. melanotheron, and greater osmoregulatory and plasticity costs at extreme salinities, where fitness-related traits are known to be altered.

Blood physiological responses and steroidogenetic effects of decreasing salinity on maturing male spotted sea bass (Lateolabrax maculatus )

“…Euryhaline fish face osmotic challenges both in freshwater and in seawater, and they have to regulate their internal water and ion concentration in order to maintain homoeostasis (Evans, 2008). Osmoregulation has been studied in many euryhaline teleosts, such as black porgy Acanthopagrus schlegeli (Tomy et al, 2009), golden pompano trachinotus ovatus (Ma et al, 2016), black-chinned tilapia (Sarotherodon melanotheron) (Tine, Guinand, & Durand, 2012) and salmonids (Flores & Shrimpton, 2012;McCormick, Regish, & Christensen, 2009). Prolactin (PRL) and its receptor (PRLR) are critical for the survival of euryhaline teleost involving in ion uptake (Juan et al, 2002;Yamaguchi et al, 2017).…”

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“…This is the first time that expression of an AFPIV is reported to occur in testes. PrePrints If the expression of the Na+/K+ ATPase (NKA) gene has been extensively studied in the gills of fish exposed to different salinities (Havird et al 2013), including S. melanotheron (Lorin-Nebel et al 2012Tine et al 2008;Tine et al 2012), this is only the first report of its expression in the testes (gene 3). In gills, NKA plays an essential role in osmoregulation through branchial ionocytes to actively uptake/excrete ions from/to environmental water, respectively.…”

“…Expression of NADH dehydrogenase was already demonstrated to significantly vary with salinity in the gills of the black-chinned tilapia (Tine et al 2010;Tine et al 2008;Tine et al 2012)), but transcripts were not annotated precisely at that time. The two differentially regulated transcripts found in this study correspond to subunits ND1 and NDUFB3/B12, whereas the two sequences used as reference correspond to subunits NDUFV1 and NDUFA10.…”

“…Analysis of the gene expression patterns in the gills of this species evidenced a clear differentiation of sub-populations along the Sine Saloum estuary (Senegal) linked to the ambient salinity (Tine et al 2012). It was also demonstrated that salinity induced phenotypic modifications of the mechanisms involved in the activation of sperm cell motility, one of the major indicators of male fitness (Fauvel et al 2010;Lahnsteiner et al 1998).…”

“…Salinity changes were shown to noticeably modify the life-histories and reproductive strategies of populations(Gueye et al. 2012; Legendre et al 2008;Panfili et al 2004;Panfili et al 2006), and to impact their osmoregulatory capacities(Lorin-Nebel et al 2012;Tine et al 2012) and their stress response(Tine et al 2010). Nevertheless, gene expression variation in reproductive organs like testes was http://dx.doi.org/10.7287/peerj.preprints.642v1 | CC-BY 4.0 Open Access | rec: 28 Nov 2014, publ: 28 Nov 2014 never investigated, although they are necessary to the preservation of male fitness and contribute to the demographic features of populations.…”