Department of Plant Sciences

Mitochondrial iron (Fe) homeostasis is important for various cellular processes including heme synthesis and Fe-S cluster synthesis, however the proteins involved in mitochondrial Fe uptake and homeostasis has not been characterized in plants. We have cloned and characterized a putative Mitochondrial Iron Transporter in rice (OsMIT). OsMIT was identified by T-DNA knockout mutant screening as a member of mitochondrial substrate carrier family and is homologous to yeast mitochondrial Fe transporters MRS3 and MRS4. OsMIT is located on rice chromosome 3 and encodes a predicted polypeptide of 329 amino acids. OsMIT-GFP protein, when expressed in tobacco BY-2 cells, was localized to the mitochondria. Yeast mrs3mrs4 double knockout mutants were used to investigate the role of OsMIT. Overexpression of OsMIT in yeast complemented the growth defect of yeast strain mrs3mrs4 under conditions of limiting Fe confirming that OsMIT plays a role in mitochondrial Fe homeostasis. Moreover, the mrs3mrs4 yeast strain expressing OsMIT accumulated comparable levels of Fe to WT in contrast to vector control which accumulated high Fe compared to WT. These results suggested that OsMIT is a mitochondrial protein involved in Fe homeostasis. The characterization of OsMIT will provide the chances to increase our understanding about mitochondrial Fe homeostasis and enable us to develop strategies to mitigate Fe deficiency stress in plants.