title: Expression of biomineralization-related ion transport genes in Emiliania huxleyi.
abstract: Biomineralization in the marine phytoplankton Emiliania huxleyi is a stringently controlled intracellular process. The molecular basis of coccolith production is still relatively unknown although its importance in global biogeochemical cycles and varying sensitivity to increased pCO₂ levels has been well documented. This study looks into the role of several candidate Ca²⁺, H⁺ and inorganic carbon transport genes in E. huxleyi, using quantitative reverse transcriptase PCR. Differential gene expression analysis was investigated in two isogenic pairs of calcifying and non-calcifying strains of E. huxleyi and cultures grown at various Ca²⁺ concentrations to alter calcite production. We show that calcification correlated to the consistent upregulation of a putative HCO₃⁻ transporter belonging to the solute carrier 4 (SLC4) family, a Ca²⁺/H⁺ exchanger belonging to the CAX family of exchangers and a vacuolar H⁺-ATPase. We also show that the coccolith-associated protein, GPA is downregulated in calcifying cells. The data provide strong evidence that these genes play key roles in E. huxleyi biomineralization. Based on the gene expression data and the current literature a working model for biomineralization-related ion transport in coccolithophores is presented.
authors: The Laboratory, Marine Biological Association of the UK, Citadel Hill, Plymouth PL1 2PB, UK. lukcki@mba.ac.uk
authors: Luke
authors: L
authors: Mackinder
authors: Glen
authors: G
authors: Wheeler
authors: Declan
authors: D
authors: Schroeder
authors: Peter
authors: P
authors: von Dassow
authors: Ulf
authors: U
authors: Riebesell
authors: Colin
authors: C
authors: Brownlee
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002119:Calcium Carbonate / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D058087:Haptophyta / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D017136:Ion Transport / Q000235:genetics*; D018895:Microsatellite Repeats; D010839:Phytoplankton / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism
chemical_list: D017920:Antiporters; D027682:Cation Transport Proteins; D027981:Symporters; C027614:calcium-hydrogen antiporters; D025262:Vacuolar Proton-Translocating ATPases; D002119:Calcium Carbonate; D002118:Calcium