Nano-Patterning of Silica: The role of select glycosyl transferases in silica patterning during biosilicification  (Collaborator:  Mark Hildebrand)
SEM of Diatom

Diatoms are single celled algae that create silica enclosures surrounding the cytoplasm. These symmetrical “glass house” cell walls are intricately decorated with pores, ridges, slits and other nanometer scale patterns in the silica. The nanotechnology industry is trying to duplicate these patterns during nanofabrication procedures to produce a variety of useful nanoscale structures including sensors, drug delivery systems, advanced coatings for air- and water-craft, etc. Our lab is working on a collaborative project with Mark Hildebrand at Scripps Institution of Oceanography to explore the involvement of polysaccharide and oligosaccharide components in patterning during biosilicification by localizing proteins important in glycosylation. It has long been known that molecules containing carboxyl groups can have favorable interactions with silica, and has been proposed that carbohydrates in the form of polysaccharides, proteoglycans or glycoproteins could play a significant role in diatom silicification.
     Recent work in Hildebrand’s lab has focused on identification and characterization of cell wall proteins and their encoding genes in T. pseudonana (Frigeri et al. 2006, and unpublished data). Lacking in these studies are approaches to evaluate the roles of carbohydrates in silica structure formation. A recently developed synchronized growth procedure for T. pseudonana enables time dependent monitoring of cell cycle events, including processes involved in cell wall synthesis. Quantization of mRNA levels using QPCR has identified a distinct pattern of mRNA expression for genes involved in cell wall synthesis (Frigeri et al. 2006). We are currently examining the expression patterns of mannosyl transferases (MT), sulfotransferases (ST), mannan synthase (ManS) and cellulose synthase-like A (CslA) and the effects of polysaccharide synthesis inhibitors during frustule deposition in Thalassiosira pseudonana. We plan to express GFP fusion constructs including mannosyl transferases (MT), sulfotransferases (ST), mannan synthase (ManS) and cellulose synthase-like A (CslA) proteins in Thalassiosira pseudonana and localize expression in real time.

Collaborator: Mark Hildebrand
at Scripps Institution of Oceanography, La Jolla, CA

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