Pituitary hormone mRNA expression in European sea bass Dicentrarchus labrax in seawater and following acclimation to fresh water

Abstract

The mRNA expression of pituitary prolactin (prl), growth hormone (gh), somatolactin (sl), proopiomelanocortin (pomc), and gonadotropins (gthI and gthII) was quantified by real-time PCR, in sea bass, Dicentrarchus labrax, adapted for 1 month to seawater (SW) or freshwater (FW). In addition, IGF-I (igfI) mRNA expression in liver and branchial Na C /K C -ATPase activity were determined. L17 ribosomal protein (rpL17) and elongation factor 1a (ef1a) were validated as reference genes in real-time PCR in the experimental context. The real-time PCR assays were validated for the different hormone genes considered. Expression of pituitary pomc, gthI, gthII, gh, and liver igfI was not significantly different between FW and SW fish. Pituitary prl was 4 . 5-fold higher in FW than in SW, whereas pituitary sl was 1 . 8-fold higher in SW-compared with FW-adapted fish. Gill Na C /K C -ATPase specific activity was 2 . 3-fold higher in FW sea bass compared with SW fish. Plasma cortisol levels were 6 . 5-fold lower in SW-than in FW-adapted specimens. The results are discussed in relation to the osmoregulatory strategy of this euryhaline SW species, which displays features that do not fit present models based on salmonids and FW euryhaline teleosts.

Reference gene selection for quantitative gene expression studies during biological invasions: A test on multiple genes and tissues in a model ascidian Ciona savignyi

“…For example, RPL17 was identified as an appropriate reference gene in the black rockfish (Sebastes schlegeli) among different tissues at larval developmental stages (Ma et al, 2013). Similarly, the expression of RPL17 did not vary in the European sea bass (Dicentrarchus labrax) collected from marine and freshwater habitats (Varsamos et al, 2006). Other members Fig.…”

Fitness difference between cryptic salinity-related phenotypes of sea bass (<em>Dicentrarchus labrax</em>)

“…Varsamos et al 2006, Terova et al 2007, Mazurais et al 2008), as they retrieved, e.g., better repeatability of C q values and efficiencies (details not reported). GHR expression was not previously investigated in sea bass.…”

“…Following Nebel et al (2005), fish were progressively acclimated to FW during a two-week period with an increment of 2‰ every day. They were reared at prevailing seasonal photoperiod and temperatures (range: 20 to 27.5°C) over the study period (early June to late October 2008), and were fed with commercial pellets according to Varsamos et al (2006).…”

“…Expression of GH was not investigated as it is only expressed in the pituitary, and variation of GH gene expression was formerly studied in Varsamos et al (2006). Primers for qPCR (Bustin et al 2009) are reported in Table 1, including primers for elongation factor-1 (EF1a) retained as reference gene in this study (rationale below).…”

“…EF1a was preliminarily retained as a reference gene as it had been previously used in studies investigating gene expression variation in response to salinity in sea bass (e.g. Varsamos et al 2006, Boutet et al 2007, Giffard-Mena et al 2008. Another reference gene traditionally used in salinity-based studies of gene expression in fish was also screened (b-actin; e.g.…”