UC San Diego

Diatoms are a highly productive group of phytoplankton collectively responsible for up to 40% of the annual organic carbon production in the world’s oceans. Photosynthetic carbon fixation by diatoms sustains diverse marine ecosystems and contributes significantly to the global carbon cycle. The natural productivity of diatoms, coupled with high hydrocarbon yield, makes this group an attractive option for the production of next-generation biofuels and other valuable bioproducts. The need for a renewable alternative to fossil fuels has recently become apparent due to the environmental and political costs of petroleum production, including the inevitability of peak oil, the costs of obtaining foreign fuel sources, and rising atmospheric CO2 levels that exacerbate climate change. However, an increased understanding of the molecular mechanisms that control intracellular carbon partitioning in diatom cells is critical to develop successful strategies to optimize future production strains.

Our current understanding of the organization and regulation of carbon metabolism in diatoms relies heavily on genomic information from a few model species. However, recent advancements in ‘omics’ analyses are expanding our understanding the dynamics of diatom metabolism based on gene expression, protein abundance, and metabolite levels. Despite increasing accessibility to these strategies, much remains to be understood about the molecular mechanisms and their regulation that underlie diatom growth productivity. Therefore, the broad objective of my dissertation is to gain further insight into the controls of intracellular carbon assimilation, partitioning, and storage in diatoms. This will be accomplished using several different approaches: a bioinformatics refinement of gene models and analysis of splicing during diatom cell cycle arrest and progression (Chapter 1), an investigation into the organization of proteins involved in photorespiratory metabolism (Chapter 2), and an investigation of the influence of a regulatory protein (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase) on intracellular carbon partitioning (Chapter 3).