Determining Fe-limited remodeling of chloroplasts in the Subarctic Pacific through “Meta-Plastid” Analyses
Kristofer M Gomes1, Sarah Lerch2, Kristen N Buck3, Mark A Brzezinski4 and Bethany D. Jenkins1, (1)University of Rhode Island, Cell and Molecular Biology, Kingston, RI, United States, (2)University of Rhode Island, Kingston, RI, United States, (3)Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, United States, (4)University of California, Marine Science Institute, Santa Barbara, CA, United States
Abstract:
Diatoms are important primary producers in the world’s oceans, yet their growth is constrained in large regions by low bioavailable iron (Fe). Fe is used as a co-factor in proteins involved in chloroplast photosynthesis and when limiting can constrain primary production. When Fe is introduced into low Fe waters, diatoms bloom and accumulate significant biomass. This bloom response indicates that diatoms possess adaptations that allow for survival in low Fe waters and for rapid growth when Fe becomes readily available. In previous work ascertaining the impacts of Fe on chloroplast function, we conducted proteomic analysis of isolated
Thalassiosira pseudonana chloroplasts grown under Fe-replete and limiting conditions. These experiments showed that Fe-limitation regulates major metabolic pathways in the chloroplast, including expression of Calvin cycle proteins and components of the photosynthetic electron transport chain.
To improve our understanding of the impacts of Fe status on diatom chloroplast function in natural communities, incubation experiments were conducted in the chronically Fe-limited Subarctic Pacific, in the context of the collaborative EXPORTS project. Metatranscriptomes generated from these incubations were compared to a reference database built from diatom homologs to the T. pseudonana chloroplast reference proteome. The metatranscriptome complement of genes encoding chloroplast proteins, is referred to as a community “Meta-plastid”. Using a similar “Meta-plastid” approach in the Fe-limited Southern Ocean we identified regulation of chloroplast function in relation to modulated Fe status, including modulation of light harvesting complex proteins and metabolic pathways such as nitrogen metabolism. Application of this approach to the Subarctic Pacific will allow us to link regulation of chloroplast function in relation to modulated Fe status and ultimately how this might relate to export potential of individual diatom taxa.
