Analysis of Arabidopsis thaliana atfer4-1, atfh and atfer4-1/atfh mutants uncovers frataxin and ferritin contributions to leaf ionome homeostasis

Ferritins are iron-storage proteins involved in the environmental and developmental control of the free iron pool within cells. Plant ferritins are targeted to mitochondria as well as to chloroplasts. AtFer4 is the Arabidopsis thaliana ferritin isoform that can be also targeted to mitochondria. Frataxin is a mitochondrial protein whose role is essential for plants; lack of AtFH frataxin causes early embryo-lethality in Arabidopsis. Because of that, the Arabidopsis atfh KO mutant is propagated in heterozygosis. For exploring the functional interaction between frataxin and ferritin, Arabidopsis double mutant atfer4-1/atfh was isolated and its physiological parameters were measured, as well as its ionome profile, together with those of both atfer4 and atfh single mutants, in different conditions of Fe supply. Impairment of both ferritin and frataxin did not lead to any effect on mitochondrial respiration. However, ionomics revealed that the content of macro- and microelements, occurring when the nutritional Fe supply changes, were altered in the mutants analysed. These results suggest that both ferritin and frataxin can contribute to the composition of the leaf ionome and also confirm ionomics as an excellent tool for detecting alterations in the plant's physiology.