Dissecting Fe Driven Changes to Metabolism in Photosynthetic Eukaryotes
EMSL Project ID
51413
Abstract
Iron (Fe) is an essential micronutrient for nearly all forms of life, because of its vital role in respiration, photosynthesis, central carbon metabolism, as well as other reactions involving electron transfer or redox chemistry. Yet, the very reactivity, which makes Fe useful for living organisms, results in its toxicity. Organisms therefore carefully regulate assimilation and distribution of Fe and adjust the amount and their inventory of Fe-containing proteins to meet variations in extracellular nutritional supply. Organisms facing Fe-limitation typically express high affinity transporters to maintain their cellular Fe quota, while inducing high capacity transporters and storage compartments in the presence of excess Fe to prepare for upcoming periods of Fe starvation. Low Fe bio-availability is the dominating condition in the field and in aquatic environments, limiting virtually all forms of life, especially phototrophic organisms, that have to meet an increased Fe demand from the highly abundant, Fe-containing protein complexes of the photosynthetic electron transfer chain. In order to study Fe metabolism in phototrophic eukaryotes, we are using the single-celled green alga Chlamydomonas reinhardtii as a reference system, because of the existing understanding of its trace metal metabolism and established methodologies monitor protein (using established pipelines at EMSL) and transcript abundance changes (RNAseq) and to trace bio-available Fe including the availability of state-of-art methods to visualize and quantify intracellular Fe.The goal of this project is to provide a cellular view of the Fe-dependent metabolism, during transitions, from Fe-luxury to-Fe economy modes and vice versa, or from photoautotrophic to (photo)heterotrophic growth in different stages of Fe nutrition. A mechanistic understanding of the diverse strategies for optimizing Fe utilization is a pre-requisite for exploiting Fe-poor environments for food and fuel production. In this context we propose to explore the proteome abundance changes in experiments designed to maximize contrast to determine the priorities of Fe utilization and the order and ways of synthesizing or degrading Fe-containing proteins. The proteome dataset will be accompanied by an analysis of newly-synthesized proteins for their bound Fe (using isotopically-pure Fe-sources), to determine the route of assembly and the utilized source of Fe, including determining the spatial distribution of specific Fe isotopes (utilizing nanoSIMS and XFM) in the same samples. In the second part we will analyze the changes in the proteome resulting from changes in the growth mode, dependent on the Fe status. Major changes to the metabolic capacities of the cell can result in changes to cofactor demand and therefore consequently require adjustments to the trace metal quota. The addition of acetate to Fe-starved, phototrophically-grown Chlamydomonas cells induces a switch from photosynthetic to heterotrophic growth, utilizing the degradation of the Fe-rich photosynthetic apparatus for eventual re-utilization in the mitochondria. We will monitor protein abundance changes during the acetate-induced switch and explore the trafficking and the priorities for Fe utilization dependent on nutrient availability. This proteomic dataset will be integrated into a larger dataset consisting of physiological parameters, transcript abundances (RNAseq) and metabolomics measurements, allowing a more complete understanding of Fe metabolism in photosynthetic eukaryotes.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2020-10-01
End Date
2023-05-05
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
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