Genome and low-iron response of an oceanic diatom adapted to chronic iron limitation
1 RD2 Marine Biogeochemistry, Helmholtz Centre for Ocean Research Kiel (GEOMAR), Düsternbrooker Weg 20, Kiel, D-24105, Germany
2 Institute of Plant Biology and Biotechnology, University of Münster, Hindenburgplatz 55, Münster, D-48143, Germany
3 Institute of Clinical Molecular Biology ICMB, Christian-Albrechts-University Kiel, Schittenhelmstrasse 12, Kiel, D-24105, Germany
4 Department of Biology, University of Bergen, Thormøhlensgt. 53 A/B, Bergen, NO-5020, Norway
5 Estonian Biocentre, University of Tartu, Riia 23b, Tartu, EE-51010, Estonia
6 Institute of Physiology, Christian-Albrechts-University Kiel, Hermann-Rodewald-Strasse 5, Kiel, D-24118, Germany
7 Faculty of Computer Science, Dalhousie University, 6050 University Avenue, Halifax, NS B3H 1W5, Canada
8 Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada
Genome Biology 2012, 13:R66 doi:10.1186/gb-2012-13-7-r66Published: 26 July 2012
Biogeochemical elemental cycling is driven by primary production of biomass via phototrophic phytoplankton growth, with 40% of marine productivity being assigned to diatoms. Phytoplankton growth is widely limited by the availability of iron, an essential component of the photosynthetic apparatus. The oceanic diatom Thalassiosira oceanica shows a remarkable tolerance to low-iron conditions and was chosen as a model for deciphering the cellular response upon shortage of this essential micronutrient.
The combined efforts in genomics, transcriptomics and proteomics reveal an unexpected metabolic flexibility in response to iron availability for T. oceanica CCMP1005. The complex response comprises cellular retrenchment as well as remodeling of bioenergetic pathways, where the abundance of iron-rich photosynthetic proteins is lowered, whereas iron-rich mitochondrial proteins are preserved. As a consequence of iron deprivation, the photosynthetic machinery undergoes a remodeling to adjust the light energy utilization with the overall decrease in photosynthetic electron transfer complexes.
Beneficial adaptations to low-iron environments include strategies to lower the cellular iron requirements and to enhance iron uptake. A novel contribution enhancing iron economy of phototrophic growth is observed with the iron-regulated substitution of three metal-containing fructose-bisphosphate aldolases involved in metabolic conversion of carbohydrates for enzymes that do not contain metals. Further, our data identify candidate components of a high-affinity iron-uptake system, with several of the involved genes and domains originating from duplication events. A high genomic plasticity, as seen from the fraction of genes acquired through horizontal gene transfer, provides the platform for these complex adaptations to a low-iron world.