Collaborative Research: Physiological and Genetic Characterization of C02 Concentrating Mechanisms in Marine Diatoms

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Approximately 50% of the photosynthesis on Earth occurs in the oceans, and diatoms are thought to be responsible for around half of this marine photosynthesis. The molecular machinery involved in the capture of light energy for photosynthesis is evolutionarily ancient and well conserved. However, the pathways for supplying the inorganic carbon that is fixed (i.e. incorporated into carbohydrates) during photosynthesis are quite diverse. These pathways, which evolved in response to a decrease in global carbon dioxide concentrations, elevate the concentration of carbon dioxide around the primary carbon-fixing enzyme RubisCO, which is both inefficient and located within the chloroplast. The goal of the proposed research is to identify and characterize the molecular components of the carbon dioxide concentrating mechanisms in Phaeodactylum tricornutum and Thalassiosira pseudonana, two marine diatoms for which whole genome sequences and genetic manipulation systems are available. A research focus will be bicarbonate transporters and carbonic anhydrases, which are known to be essential components of the carbon dioxide concentrating mechanisms. While these have been identified in the P. tricornutum and T. pseudonana genomes using computational approaches, there is little cytological or functional verification of the computational predictions. A variety of methods including microscopy, immunolocalization, over-expression of native protein-fluorescent protein fusions, RNA interference based expression knockdown, and membrane inlet mass spectrometry will be used to connect cytological and functional information to genomic entities. Such information will facilitate an extension to other diatoms as genomes or transcriptomes become available. The data will be used to test and refine conceptual models of the function of the carbon dioxide concentrating mechanisms.Broader ImpactsA graduate student and undergraduate students will be trained at the intersection of phytoplankton physiology and genetics. The wider community will be engaged through a collaboration with the Centers for Ocean Sciences Education Excellence-South East in which the investigators will collaborate with K-12 teachers and outreach specialists to develop materials on ocean acidification for use in K-12 classrooms.