Borrowed Chloroplasts: Secondary Endosymbiosis and the Chromalveolates
Jenkins, Bethany D. , Pritchard, LeAnn B. , Parker, Micaela S. , Rynearson, Tatiana A. , Armbrust, E. Virginia .
Diatom life histories, ecology and nutrient metabolism unveiled by genomics.
Diatoms are important photosynthetic unicellular organisms in both marine and freshwater environments. Diatoms are a member of the heterokont algae within the chromalveolate supergroup. Historical classifications of diatoms are based on morphologies of their silicified cell walls (frustules). Diatoms evolved as a result of secondary endosymbiosis whereby a eukaryotic host engulfed a red alga. The recently completed complete genome sequences of diatoms from two different classes, Thalassiosira pseudonana and Phaeodactylum tricornutum, illuminate the complex life histories of this protist group. This presentation will focus on nutrient acquisition pathways and describe how diatoms have aspects of metabolism that are derived from both plant and animal origins. Differences in nutrient uptake pathways between diatoms will also be highlighted, particularly with respect to carbon concentrating mechanisms and trace metal metabolism. To better understand how T. pseudonana and unsequenced pennate diatom (Pseudo-nitzschia spp.) species regulate nutrient uptake pathways, we have been assaying gene expression under various culture treatments including silicate and trace metal limitation using cDNA subtraction libraries and quantitative reverse-transcriptase PCR approaches. Analysis of ESTs expressed in silicate-limited Pseudo-nitzschia australis indicate genes related to silicate uptake metabolism and other nutrient transporters are upregulated. Expression studies of these transporters under other nutrient stressors reveal both nutrient-specific expression patterns and others genes whose expression may be indicate a universal stress response. Genes important for trace metal metabolism appear to be controlled by day/night cycles as well, indicating a linkage between photochemistry and trace metal uptake. Therefore, genome sequence data provides an invaluable blueprint for motivating studies of gene function to understand the metabolic and ecological roles of diatoms.
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Jenkins laboratory website
Rynearson laboratory website
Armbrust laboratory website
Thalassiosira pseudonana genome site
Phaeodactylum tricornutum genome site
1 - University of Rhode Island, Cell and Molecular Biology and Graduate School of Oceanography, 316 Morrill Halll, 45 Lower College Rd., Kingston, RI, 02881, USA
2 - University of Rhode Island, Cell and Molecular Biology, Morrill Hall, 45 Lower College Rd., Kingston, RI, 02881, USA
3 - University of Washington, School of Oceanography, Box 357940, Seattle, WA, 98195, USA
4 - University of Rhode Island, Graduate School of Oceanography, Narragansett Bay Campus, Narragansett, RI, 02882, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Waldorf Room/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:30 AM