Marine & Environmental Biology Seminar Series

Dr. Andrew Allen
Scripps Institution of Oceanography, UC San Diego
J. Craig Venter Institute
Lab website

Iron Bioavailability in High-CO2 Oceans and Other Vignettes: New Perspectives on Genomics and Metabolism in Diatoms

February 20
12:00 PM
AHF 153 (Torrey Webb Room)

Abstract: It has become increasingly clear that iron availability plays a major role in regulating phytoplankton assemblages in HNLC regions. However there remains a large degree of uncertainty related to how eukaryotic marine phytoplankton acquire iron from the environment. Genome enabled functional studies have since revealed insights into key iron acquisition pathways, including the key ferric iron concentrating protein ISIP2a. To better characterize the functionality and substrate specificity of ISIP2a and other Fe sensitive proteins we have initiated systematic reverse genetics studies in the model diatom P. tricornutum. These data suggest that diatoms utilize distinct pathways for assimilation of different forms of dissolved iron including uncomplexed inorganic ferric iron, organically complexed iron and highly transient ferrous iron. New data also suggest that carbonate ions are required for activity of the ferric iron assimilation system, suggesting that ocean acidification might affect iron uptake and the relative contribution of distinct iron acquisition pathways. Phylogenetic analysis suggests that ISIP2a is transferrin, ‘phytotransferrin’, which independently and convergently evolved carbonate-coordinated ferric iron binding. Therefore, in response to predicted increases seawater, temperature, atmospheric pCO2 and associated decreases in the pH of seawater we expect a shift to occur in relative usage of iron acquisition strategies to increase the importance of usage of complexed- and siderophore-bound iron. Also, new findings which suggest that simple sequence requirements may enable DNA from foreign sources to persist in the diatom nucleus as extrachromosomal episomes, revealing a potential mechanism for organellar and foreign DNA acquisition, will be discussed. Additionally, new findings related to nitrogen metabolism in diatoms will be presents.