The atfer4 ferritin is a key component for the control of the iron homeostasis in mitochondria of arabidopsis cells

Although iron has a major role in mitochondrial activity, the processes of iron transport, trafficking and homeostasis in plant mitochondria are mostly unknown. According to computer analysis, AtFer4 is the ferritin isoform with highest scores for localization in mitochondria. We isolated and characterized two independent Arabidopsis atfer4 mutants knock out in the AtFer4 isoform. Analysis of plant phenotypes show no alteration of phenotype attributable to lack of AtFer4. However, when grown in suspension cultures, atfer4 mutants show impaired growth and higher cell death. We show that ATFER4 is mitochondria-localized, that it accumulates in mitochondria regardless of exogenous iron treatment and that at least another ferritin isoform, different from ATFER4, accumulates in mitochondria of irontreated atfer4 and wt Col cells. Interestingly, atfer4 mitochondria accumulate more iron than wt ones, in all conditions tested. All these results indicate that AtFer4 has a key role for the iron trafficking/homeostasis in mitochondria in conditions in which such organelles are the sole energy source, that is in suspension cultured cells.