CAREER: Investigation of the Cellular and Physiological Effects of Chloroplast/Mitochondrial Iron Export in Plants

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2)

Iron is a mineral nutrient required for virtually all forms of life, including plants. However, iron is toxic when present in excess or improperly distributed within the cell or the organism. To cope with such paradox, organisms have evolved delicate strategies to tightly control iron.

Uncovering the processes of iron regulation will generate knowledge fundamental to biology. Meanwhile, iron deficiency is a serious public health issue that affects nearly half of the global population. Staple crops, which are not rich sources of iron, are the main dietary source of iron worldwide.

Therefore, to sustainably solve iron malnutrition, it is essential to understand the molecular mechanisms of iron regulation in plants and apply the knowledge for biofortification, the process of enhancing nutritional value of crops via selective breeding or genetic engineering. This project focuses on investigating iron regulation in plant mitochondria and chloroplasts, which are specialized intracellular compartments central to plant metabolism and require high levels of iron for their function.

The expected outcomes of this project will provide knowledge significant for its scientific merit and critical insights that can be applied to improve agriculture and human health. Furthermore, the proposed educational activities to enhance authentic research experience for undergraduate students and the community-based learning non-major biology course for K-12 outreach will foster the growth of next generation scientists and science communicators.

Mitochondria and chloroplasts are the site of vital metabolic processes that require iron. These organelles are also involved in sensing iron and integrating signals to coordinate metabolic and physiological responses to changes in iron levels. Meanwhile, iron must be tightly controlled in the mitochondria and chloroplasts, as they are prone to damage caused by the highly reactive nature of dysregulated iron under aerobic conditions.

This project investigates iron regulation in plant mitochondria and chloroplasts, and its impact at the cellular and physiological levels, by examining Arabidopsis mutants defective in exporting iron from the mitochondria and chloroplasts. Specifically, abnormal membrane invaginations detected in iron-deficient mutants defective in mitochondrial and chloroplast iron export will be analyzed to test the hypothesis that these structures contribute to intercellular iron transport using cell biology and advanced imaging techniques.

Membrane trafficking has not been previously studied in the context of mitochondrial and chloroplast iron and will advance our understanding of the molecular mechanisms of plant iron homeostasis. The potential functional interactions between the chloroplast/mitochondrial iron exporter and proteins that sequester iron in chloroplasts and mitochondria will also be investigated using molecular genetics, biochemistry, and proteomic approaches.

Such analyses will provide critical knowledge on inter-organellar iron homeostasis in mitochondria and chloroplasts. Overall, this project incorporates multi-disciplinary approaches and will contribute towards a more comprehensive understanding of plant iron homeostasis.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.