Characterization of a New Protein Family Associated With the Silica Deposition Vesicle Membrane Enables Genetic Manipulation of Diatom Silica

Micrographs showing distal surfaces of valves
TitleCharacterization of a New Protein Family Associated With the Silica Deposition Vesicle Membrane Enables Genetic Manipulation of Diatom Silica
Publication TypeJournal Article
Year of Publication2017
AuthorsTesson B, Lerch S.JL, Hildebrand M
JournalScientific Reports
Date Published2017/10
Type of ArticleArticle
ISBN Number2045-2322
Accession NumberWOS:000413188400038
Keywordsbiosilica; cell-cycle; evolution; image-analysis; messenger-rna; metabolism; silaffins; silicification; thalassiosira-pseudonana bacillariophyceae; valve morphogenesis

Diatoms are known for their intricate, silicified cell walls (frustules). Silica polymerization occurs in a compartment called the silica deposition vesicle (SDV) and it was proposed that the cytoskeleton influences silica patterning through the SDV membrane (silicalemma) via interactions with transmembrane proteins. In this work we identify a family of proteins associated with the silicalemma, named SAPs for Silicalemma Associated Proteins. The T. pseudonana SAPs (TpSAPs) are characterized by their motif organization; each contains a transmembrane domain, serine rich region and a conserved cytoplasmic domain. Fluorescent tagging demonstrated that two of the TpSAPs were localized to the silicalemma and that the intralumenal region of TpSAP3 remained embedded in the silica while the cytoplasmic region was cleaved. Knockdown lines of TpSAP1 and 3 displayed malformed valves; which confirmed their roles in frustule morphogenesis. This study provides the first demonstration of altering silica structure through manipulation of a single gene.

Short TitleSci Rep

The ability of diatoms to control the deposition of silica with high precision and reproducibility in a membranous compartment is unique. Deciphering the genetic basis of how diatoms make reproducible structures is an important step to elucidate this process. Several soluble proteins able to precipitate silica have been discovered over the last few decades. However, the mechanisms by which the final three-dimensional cell wall patterns are formed remain unknown. This work describes a family of transmembrane proteins localized to the SDV membrane and involved in mesoscale silica structure formation and patterning, as well as the first genetic alterations of silica structure through the manipulation of individual genes. The demonstration of specific phenotypes generated with knockdowns of TpSAP1 and 3 opens the door towards characterizing their roles in more detail.

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