title: Silica transport in the demosponge Suberites domuncula: fluorescence emission analysis using the PDMPO probe and cloning of a potential transporter.
abstract: Silicon is, besides oxygen, the most abundant element on earth. Only two taxa use this element as a major constituent of their skeleton, namely sponges (phylum Porifera) and unicellular diatoms. Results from combined cytobiological and molecularbiological techniques suggest that, in the demosponge Suberites domuncula, silicic acid is taken up by a transporter. Incubation of cells with the fluorescent silica tracer PDMPO [2-(4-pyridyl)-5-[[4-(2-dimethylaminoethylaminocarbamoyl)methoxy]phenyl]-oxazole] showed a response to silicic acid by an increase in fluorescence; this process is temperature-dependent and can be blocked by DIDS (4,4-di-isothiocyanatostilbene-2,2-disulphonic acid). The putative NBC (Na+/HCO3-) transporter was identified, cloned and analysed. The deduced protein comprises all signatures characteristic of those molecules, and phylogenetic analysis also classifies it to the NBC transporter family. This cDNA was used to demonstrate that the expression of the gene is strongly up-regulated after treatment of cells with silicic acid. In situ hybridization demonstrated that the expression of the sponge transporter occurs in those cells that are located adjacent to the spicules (the skeletal element of the animal) or in areas in which spicule formation occurs. We conclude that this transporter is involved in silica uptake and have therefore termed it the NBCSA [Na+/HCO3-[Si(OH)4]] co-transporter.
authors.affiliation: Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099 Mainz, Federal Republic of Germany.
authors.forename: Heinz-C
authors.initials: HC
authors.lastname: Schröder
authors.forename: Sanja
authors.initials: S
authors.lastname: Perović-Ottstadt
authors.forename: Matthias
authors.initials: M
authors.lastname: Rothenberger
authors.forename: Matthias
authors.initials: M
authors.lastname: Wiens
authors.forename: Heiko
authors.initials: H
authors.lastname: Schwertner
authors.forename: Renato
authors.initials: R
authors.lastname: Batel
authors.forename: Michael
authors.initials: M
authors.lastname: Korzhev
authors.forename: Isabel M
authors.initials: IM
authors.lastname: Müller
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology*; D015152:Blotting, Northern / Q000379:methods; D002478:Cells, Cultured; D003001:Cloning, Molecular / Q000379:methods*; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods; D026901:Membrane Transport Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010080:Oxazoles / Q000378:metabolism*; D010802:Phylogeny; D011161:Porifera / Q000737:chemistry* / Q000166:cytology / Q000235:genetics; D012313:RNA / Q000235:genetics; D020539:Sequence Analysis, Protein / Q000379:methods; D017386:Sequence Homology, Amino Acid; D012824:Silicic Acid / Q000737:chemistry; D012822:Silicon Dioxide / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics; D027981:Symporters / Q000235:genetics*
chemical_list: C120434:2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; D010080:Oxazoles; C422023:SLC4A5 protein, human; D027982:Sodium-Bicarbonate Symporters; D027981:Symporters; D012824:Silicic Acid; D012313:RNA; D012822:Silicon Dioxide