Regulation of iron-homeostasis in the chloroplast of Chlamydomonas reinhardtii: Dynamic remodeling of the photosynthetic machinery in response to iron availability

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Iron-deficiency is a serious nutritional problem for nearly all forms of life because the limited bioavailability of iron despite its natural abundance. The bioenergetic membranes of respiration and photosynthesis are a major cellular sink for iron because of the abundance of heme and iron-sulfur proteins in these pathways. A question addressed in this project is how redox energy metabolism is modified in response to various degrees of iron-deficiency. It is proposed to use the photosynthetic apparatus of the green alga Chlamydomonas reinhardtii as the experimental model because we can apply reverse genetics and whole systems approaches like proteomics to this problem. The proposal is designed to test the following hypothesis: There is a regulatory network that induces specific responses before an iron-deficiency dependent chlorotic phenotype becomes evident. This network senses the cellular or sub-cellular iron content and controls protein expression levels to regulate various processes including iron homeostasis and the remodeling process of the photosynthetic machinery. We will elucidate regulatory networks that operate in chloroplast iron-homeostasis with a focus on mechanisms that modulate bioenergetic pathways in the plastids in response to iron-deficiency and in particular on mechanisms that control and establish remodeling of photosystem I (PSI) and its light-harvesting proteins (LHCI).