Mitochondrial localization of Arabidopsis thaliana Isu Fe–S scaffold proteins

Isu are scaffold proteins involved in iron–sulfur cluster biogenesis and playing a key role in yeast mitochondria and Escherichia coli. In this work, we have characterized the Arabidopsis thaliana Isu gene family. AtIsu1,2,3 genes encode polypeptides closely related to their bacterial and eukaryotic counterparts. AtIsu expression in a Saccharomyces cerevisiae Δisu1Δnfu1 thermosensitive mutant led to the growth restoration of this strain at 37 °C. Using Isu-GFP fusions expressed in leaf protoplasts and immunodetection in organelle extracts, we have shown that Arabidopsis Isu proteins are located only into mitochondria, supporting the existence of an Isu-independent Fe–S assembly machinery in plant plastids.