title: Selenium affects biosilica formation in the demosponge Suberites domuncula. Effect on gene expression and spicule formation.
abstract: Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repeats of 20 amino acids, composed of 10 distinct hydrophobic regions ( approximately 9 amino acids in length). Recombinant proteins were prepared, and antibodies were raised against these two proteins. Both were found to stain the central axial filament, which comprises the silicatein, as well as the surface of the spicules. In the presence of selenium, only the genes for selenoprotein M and spicule-associated protein are up-regulated, whereas the expression of the silicatein gene remains unchanged. Finally we show that, in the presence of selenium, larger silica aggregates are formed. We conclude that selenium has a stimulatory effect on the formation of siliceous spicules in sponges, and it may be involved in the enzymatic synthesis of biosilica components.
authors.affiliation: Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Mainz, Germany. wmueller@uni-mainz.de
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
authors.forename: Alexandra
authors.initials: A
authors.lastname: Borejko
authors.forename: David
authors.initials: D
authors.lastname: Brandt
authors.forename: Ronald
authors.initials: R
authors.lastname: Osinga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ushijima
authors.forename: Bojan
authors.initials: B
authors.lastname: Hamer
authors.forename: Anatoli
authors.initials: A
authors.lastname: Krasko
authors.forename: Cao
authors.initials: C
authors.lastname: Xupeng
authors.forename: Isabel M
authors.initials: IM
authors.lastname: Müller
authors.forename: Heinz C
authors.initials: HC
authors.lastname: Schröder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D001483:Base Sequence; D015153:Blotting, Western; D002403:Cathepsins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005979:Glutathione Peroxidase / Q000378:metabolism; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics; D012643:Selenium / Q000494:pharmacology*; D051140:Selenoproteins; D012822:Silicon Dioxide / Q000378:metabolism*; D047233:Suberites / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D015854:Up-Regulation / Q000187:drug effects* / Q000235:genetics
chemical_list: D000906:Antibodies; D011506:Proteins; D051140:Selenoproteins; C112571:silicatein alpha; D012822:Silicon Dioxide; D005979:Glutathione Peroxidase; D002403:Cathepsins; D012643:Selenium