title: Genome and transcriptome analyses provide insight into the euryhaline adaptation mechanism of Crassostrea gigas.
abstract: BACKGROUND
  The Pacific oyster, Crassostrea gigas, has developed special mechanisms to regulate its osmotic balance to adapt to fluctuations of salinities in coastal zones. To understand the oyster's euryhaline adaptation, we analyzed salt stress effectors metabolism pathways under different salinities (salt 5, 10, 15, 20, 25, 30 and 40 for 7 days) using transcriptome data, physiology experiment and quantitative real-time PCR.
  
  
  RESULTS
  Transcriptome data uncovered 189, 480, 207 and 80 marker genes for monitoring physiology status of oysters and the environment conditions. Three known salt stress effectors (involving ion channels, aquaporins and free amino acids) were examined. The analysis of ion channels and aquaporins indicated that 7 days long-term salt stress inhibited voltage-gated Na(+)/K(+) channel and aquaporin but increased calcium-activated K(+) channel and Ca(2+) channel. As the most important category of osmotic stress effector, we analyzed the oyster FAAs metabolism pathways (including taurine, glycine, alanine, beta-alanine, proline and arginine) and explained FAAs functional mechanism for oyster low salinity adaptation. FAAs metabolism key enzyme genes displayed expression differentiation in low salinity adapted individuals comparing with control which further indicated that FAAs played important roles for oyster salinity adaptation. A global metabolic pathway analysis (iPath) of oyster expanded genes displayed a co-expansion of FAAs metabolism in C. gigas compared with seven other species, suggesting oyster's powerful ability regarding FAAs metabolism, allowing it to adapt to fluctuating salinities, which may be one important mechanism underlying euryhaline adaption in oyster. Additionally, using transcriptome data analysis, we uncovered salt stress transduction networks in C. gigas.
  
  
  CONCLUSIONS
  Our results represented oyster salt stress effectors functional mechanisms under salt stress conditions and explained the expansion of FAAs metabolism pathways as the most important effectors for oyster euryhaline adaptation. This study was the first to explain oyster euryhaline adaptation at a genome-wide scale in C. gigas.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Meng
authors.forename: Qihui
authors.initials: Q
authors.lastname: Zhu
authors.forename: Linlin
authors.initials: L
authors.lastname: Zhang
authors.forename: Chunyan
authors.initials: C
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Zhicai
authors.initials: Z
authors.lastname: She
authors.forename: Baoyu
authors.initials: B
authors.lastname: Huang
authors.forename: Guofan
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D049896:Crassostrea / Q000502:physiology*; D020869:Gene Expression Profiling / Q000379:methods; D005819:Genetic Markers; D016678:Genome / Q000502:physiology*; D009997:Osmotic Pressure / Q000502:physiology; D010140:Pacific Ocean; D054712:Salinity; D059467:Transcriptome / Q000502:physiology
chemical_list: D005819:Genetic Markers
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