A differentially expressed enolase gene isolated from the gilthead sea bream ( Sparus aurata) under high-density conditions is up-regulated in brain after in vivo lipopolysaccharide challenge

Abstract

To investigate the effect of different population densities on gene transcription in the sea bream brain ( Sparus aurata), the messenger RNA (mRNA) differential display (DD) technique was used to analyse gene expression. Sea bream were held at different densities, 6 or 26 kg m −3, over a period of 14 days. We identified seven differentially expressed sequences of which one sequence was functionally identified. The S. aurata enolase gene homologue (S-enolase), pertaining to the alpha non-neuronal enolase group of the enzyme superfamily, was up-regulated in the brain of fish in the high-density population group. S-enolase mRNA expression was also found in other tissues including heart, liver and head kidney suggesting a ubiquitous nature. Furthermore, brain S-enolase mRNA is highly up-regulated 48 h after intra-peritoneal bacterial lipopolysaccharide (LPS) administration. Therefore, S-enolase gene expression is linked to the incidence of different stressors, density and infective agents, in the sea bream and may be a potential molecular biomarker for stress diagnosis in this fish.