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A Functional Genomic Analysis of Diatom Glycobiology (Dr. T. Chiovitti)
The broad aims are to develop an understanding of carbohydrate metabolism and the mechanisms involved in the control and regulation of polysaccharide synthesis and degradation in diatoms. Using the model species, Thalassiosirapseudonana, a planktonic centric diatom, the specific objectives are to:
(1) Identify genes encoding enzymes involved in carbohydrate metabolism and the synthesis and degradation of diatom polysaccharides.
(2) Characterize the activity of diatom enzymes to obtain proof of function.
(3) Determine the biological significance of enzymes involved in the synthesis of the polysaccharides by investigating their expression and localization patterns.
(4) Characterize secreted extracellular polysaccharides of the model species.
Diatoms are a ubiquitous group of unicellular microalgae that are major primary producers in most aquatic habitats. Diatoms annually produce up to 25% of the ca. 50 billion tonnes of carbon fixed in the world’s oceans and they are the dominant group of organisms involved in the global turnover of biogenic silica. Knowledge about their carbohydrate metabolism and the control of polysaccharide synthesis is fundamental to understanding the biology of diatoms and a prerequisite for the development of niche biotechnology. Diatom extracellular polysaccharides have potential applications in the nanofabrication of silica composites, and in therapeutics and agronomics that utilize modified chitin oligosaccharides. However, diatoms are also the most frequent and successful microalgal biofoulers of submerged artificial surfaces, and the accumulation of diatom cells and their extracellular polymers (i.e., a biofilm) adversely impact on human aquatic enterprises, such as commercial shipping. We have begun a program of research investigating the composition, structure, and biological significance of diatom polysaccharides, and have made excellent progress in characterizing the extracellular polysaccharides and adhesive glycoproteins of several diatom species, as well as clarifying the intracellular origin of glucans that were previously inferred to be extracellular. Owing to our expertise in the composition and structure of diatom polysaccharides, we were invited to participate in the international collaboration to sequence and annotate the first diatom genome (T. pseudonana). This provides the lab with an unprecedented opportunity to identify genes encoding the enzymes involved in polysaccharide synthesis, modification, and degradation, and ultimately to build the links between polysaccharide biosynthesis, chemistry, and function.
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