title: Transcriptome profiling reveals that feeding wild zooplankton to larval Atlantic cod (Gadus morhua) influences suites of genes involved in oxidation-reduction, mitosis, and selenium homeostasis.
abstract: BACKGROUND
  Larval nutrition and growth are key issues for wild and cultured cod. While it was shown previously that larval cod fed wild zooplankton grow faster than those fed only rotifers, the mechanisms involved in this enhanced growth are not completely understood. We used microarrays to identify larval cod transcripts that respond to feeding with small amounts of wild zooplankton (5-10 % of live prey items). The larval transcriptome was compared between 3 treatment groups [fed rotifers (RA), rotifers with protein hydrolysate (RA-PH), or rotifers with zooplankton (RA-Zoo)] at 9-10 mm length [26-30 days post-hatch (dph)] to identify a robust suite of zooplankton-responsive genes (i.e. differentially expressed between RA-Zoo and both other groups).
  
  
  RESULTS
  The microarray experiment identified 147 significantly up-regulated and 156 significantly down-regulated features in RA-Zoo compared with both RA and RA-PH. Gene ontology terms overrepresented in the RA-Zoo responsive gene set included "response to selenium ion" and several related to cell division and oxidation-reduction. Ten selenoprotein-encoding genes, and 2 genes involved in thyroid hormone generation, were up-regulated in RA-Zoo compared with both other groups. Hierarchical clustering of RA-Zoo responsive genes involved in oxidation-reduction and selenium homeostasis demonstrated that only the zooplankton treatment had a considerable and consistent impact on the expression of these genes. Fourteen microarray-identified genes were selected for QPCR involving 9-13 mm larvae, and 13 of these were validated as differentially expressed between RA-Zoo and both other groups at ~9 mm. In contrast, in age-matched (34-35 dph; ~11 mm RA and RA-PH, ~13 mm RA-Zoo) and size-matched (~13 mm) older larvae, only 2 and 3 genes, respectively, showed the same direction of RA-Zoo-responsive change as in ~9 mm larvae.
  
  
  CONCLUSIONS
  The modulation of genes involved in selenium binding, redox homeostasis, and thyroid hormone generation in ~9 mm RA-Zoo larvae in this study may be in response to the relatively high levels of selenium, iodine, and LC-PUFA (potentially causing oxidative stress) in zooplankton. Nonetheless, only a subset of zooplankton-responsive genes in ~9 mm larvae remained so in older larvae, suggesting that the observed transcriptome changes are largely involved in initiating the period of growth enhancement.
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. mrise@mun.ca.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Rise
authors.affiliation: Aquatic Research Cluster, CREAIT Network, Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. jrhall@mun.ca.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Hall
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. gnash@mun.ca.
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Nash
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. xi.xue@mun.ca.
authors.forename: Xi
authors.initials: X
authors.lastname: Xue
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. Marije.Booman@dfo-mpo.gc.ca.|Present address: Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, BC, V9T 6N7, Canada. Marije.Booman@dfo-mpo.gc.ca.
authors.forename: Marije
authors.initials: M
authors.lastname: Booman
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. tomer.katan@goldeneaglesablefish.com.
authors.forename: Tomer
authors.initials: T
authors.lastname: Katan
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. kgamperl@mun.ca.
authors.forename: A Kurt
authors.initials: AK
authors.lastname: Gamperl
mesh_terms: D000818:Animals; D048389:Gadus morhua / Q000235:genetics*; D020869:Gene Expression Profiling; D008938:Mitosis / Q000235:genetics; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000235:genetics; D015048:Zooplankton
chemical_list: D012333:RNA, Messenger