title: Liver transcriptome analysis in gilthead sea bream upon exposure to low temperature.
abstract: BACKGROUND
  Water temperature greatly influences the physiology and behaviour of teleost fish as other aquatic organisms. While fish are able to cope with seasonal temperature variations, thermal excursions outside their normal thermal range might exceed their ability to respond leading to severe diseases and death.Profound differences exist in thermal tolerance across fish species living in the same geographical areas, promoting for investigating the molecular mechanisms involved in susceptibility and resistance to low and high temperatures toward a better understanding of adaptation to environmental challenges. The gilthead sea bream, Sparus aurata, is particularly sensitive to cold and the prolonged exposure to low temperatures may lead to the "winter disease", a metabolic disorder that significantly affects the aquaculture productions along the Northern Mediterranean coasts during winter-spring season. While sea bream susceptibility to low temperatures has been extensively investigated, the cascade of molecular events under such stressful condition is not fully elucidated.
  
  
  RESULTS
  In the present study two groups of wild sea bream were exposed for 21 days to two temperature regimes: 16 ± 0.3°C (control group) and 6.8 ± 0.3°C (cold-exposed group) and DNA microarray analysis of liver transcriptome was carried out at different time points during cold exposure.A large set of genes was found to be differentially expressed upon cold-exposure with increasingly relevant effects being observed after three weeks at low temperature. All major known responses to cold (i.e. anti-oxidant response, increased mitochondrial function, membrane compositional changes) were found to be conserved in the gilthead sea bream, while, evidence for a key role of unfolded protein response (UPR) to endoplasmic reticulum (ER) stress, during short- and long-term exposure to cold is reported here for the first time.
  
  
  CONCLUSIONS
  Transcriptome data suggest a scenario where oxidative stress, altered lipid metabolism, ATP depletion and protein denaturation converge to induce ER stress. The resulting UPR activation further promotes conditions for cell damage, and the inability to resolve ER stress leads to severe liver dysfunction and potentially to death.
authors.forename: Alba N
authors.initials: AN
authors.lastname: Mininni
authors.affiliation: Department of Comparative Biomedicine and Food Science, University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy. massimo.milan@unifi.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Milan
authors.forename: Serena
authors.initials: S
authors.lastname: Ferraresso
authors.forename: Tommaso
authors.initials: T
authors.lastname: Petochi
authors.forename: Patrizia
authors.initials: P
authors.lastname: Di Marco
authors.forename: Giovanna
authors.initials: G
authors.lastname: Marino
authors.forename: Silvia
authors.initials: S
authors.lastname: Livi
authors.forename: Chiara
authors.initials: C
authors.lastname: Romualdi
authors.forename: Luca
authors.initials: L
authors.lastname: Bargelloni
authors.forename: Tomaso
authors.initials: T
authors.lastname: Patarnello
mesh_terms: D000818:Animals; D003080:Cold Temperature; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008099:Liver / Q000378:metabolism*; D015203:Reproducibility of Results; D021541:Sea Bream / Q000235:genetics*; D013997:Time Factors; D059467:Transcriptome