Genome-based Approaches for Understanding Nutritional Iron Homeostasis in Chlamydomonas reinhardtii

  • Iron is an essential nutrient for all life forms, including plants, but of limiting availability in many environments, affecting productivity of both food production and carbon capturing. Iron is essential because of its broad function as a catalyst of redox reactions and processes involving O2 chemistry in the catalytic centers of enzymes. Because of the nature of these reactions, excess amounts of the nutrient can be toxic, requiring a fine tuning of the cellular iron content, to both accommodate the essential demand and avoid detrimental effects simultaneously. A question of this project is how plant metabolism is modified in iron-deficient conditions, for which the green alga Chlamydomonas reinhardtii as a microbe is an excellent reference organism. The metabolic flexibility of C. reinhardtii, specifically the capacity for both heterotrophic (on acetate) and autotrophic (on CO2) growth, offers a unique opportunity to distinguish the impact of iron nutrition on photosynthetic versus respiratory metabolism. During steady-state photoheterotrophic Fe-limited growth, where the cells are provided with light, CO2, and acetate, but lack extracellular iron, cells maintain respiration while decreasing photosynthetic contribution to the energetics of the cell. This thesis analyzes the transition from photoautotrophic (light and CO2) to photoheterotrophic cultures in the context of Fe-nutrition by adding a reduced carbon source to phototrophic cultures and assessing the developing changes to the metabolism time-dependently, in various levels of readouts. Based on the transcriptome analysis, all major cellular processes and pathways respond to the availability of acetate, but Fe-limited cells specifically sacrifice photosynthetic capacity towards respiratory activity in the first 12h after the additional carbon source becomes available, allowing to gain mechanistic insights of transitioning between different ways of life, dependent on the nutritional makeup of the environment. Secondly, exposure to high extracellular iron amounts, its opportunities, and the mechanisms of avoiding deleterious effects as a result from it, had been under-investigated before the beginning of this thesis. Physiological and photosynthetic parameters, elemental analysis, transcriptomics, and a mutant depleted of functional acidic vacuoles, proposed to be involved in the storage for transition metals, were utilized to further the understanding of the processes. Altogether, the results presented in this thesis illustrate how C. reinhardtii can be successfully used as a model organism to study a large variety of aspects of cell and molecular biology, including dynamic acclimations to changing environments.

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Author:Anne Glaesener
URN (permanent link):urn:nbn:de:hbz:386-kluedo-64392
Advisor:Michael Schroda
Document Type:Doctoral Thesis
Language of publication:English
Publication Date:2021/06/29
Year of Publication:2021
Publishing Institute:Technische Universität Kaiserslautern
Granting Institute:Technische Universität Kaiserslautern
Acceptance Date of the Thesis:2019/11/26
Date of the Publication (Server):2021/06/29
Number of page:VIII, 220
Faculties / Organisational entities:Fachbereich Biologie
DDC-Cassification:5 Naturwissenschaften und Mathematik / 570 Biowissenschaften, Biologie
Licence (German):Creative Commons 4.0 - Namensnennung, nicht kommerziell, keine Bearbeitung (CC BY-NC-ND 4.0)