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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pseudonana (Frigeri et al. 2006, and unpublished data).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.
http://sio.ucsd.edu/
Collaborator: Mark Hildebrand
at Scripps Institution of Oceanography, La Jolla, CA |
