Seasonal freeze resistance of rainbow smelt (Osmerus mordax) is generated by differential expression of glycerol-3 phospahte dehydrogenase, phosoenol pyruvate carboxykinase and antifreeze protein genes

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DOIResolve DOI: http://doi.org/10.1086/499981
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TypeArticle
Journal titlePhysiological and Biochemical Zoology
Volume79
Issue2
Pages411423; # of pages: 13
Subjectantifreeze; proteins; gene expression regulation; genetics; glycerolphosphate; dehydrogenase; osmeriformes; osmeriformes metabolism; phosphoenolpyruvate; GTP; carboxykinase; seasons
AbstractIn winter, rainbow smelt (Osmerus mordax) accumulate glycerol and produce an antifreeze protein (AFP), which both contribute to freeze resistance. The role of differential gene expression in the seasonal pattern of these adaptations was investigated. First, cDNAs encoding smelt and Atlantic salmon (Salmo salar) phosphoenolpyruvate carboxykinase (PEPCK) and smelt glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were cloned so that all sequences required for expression analysis would be available. Using quantitative PCR, expression of beta actin in rainbow smelt liver was compared with that of GAPDH in order to determine its validity as a reference gene. Then, levels of glycerol-3-phosphate dehydrogenase (GPDH), PEPCK, and AFP relative to beta actin were measured in smelt liver over a fall-winter-spring interval. Levels of GPDH mRNA increased in the fall just before plasma glycerol accumulation, implying a driving role in glycerol synthesis. GPDH mRNA levels then declined during winter, well in advance of serum glycerol, suggesting the possibility of GPDH enzyme or glycerol conservation in smelt during the winter months. PEPCK mRNA levels rose in parallel with serum glycerol in the fall, consistent with an increasing requirement for amino acids as metabolic precursors, remained elevated for much of the winter, and then declined in advance of the decline in plasma glycerol. AFP mRNA was elevated at the onset of fall sampling in October and remained elevated until April, implying separate regulation from GPDH and PEPCK. Thus, winter freezing point depression in smelt appears to result from a seasonal cycle of GPDH gene expression, with an ensuing increase in the expression of PEPCK, and a similar but independent cycle of AFP gene expression.
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Copyright notice© 2006 by The University of Chicago. All rights reserved.
LanguageEnglish
AffiliationNRC Institute for Marine Biosciences; National Research Council Canada
Peer reviewedYes
NRC number55508
1558
NPARC number3538380
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Record identifierd3aeec66-1020-42cf-b7f1-f176c40c4495
Record created2009-03-01
Record modified2016-05-09
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