Functional analysis of Arabidopsis genes involved in mitochondrial iron–sulfur cluster assembly

Machinery for the assembly of the iron–sulfur ([Fe–S]) clusters that function as cofactors in a wide variety of proteins has been identified in microbes, insects, and animals. Homologs of the genes involved in [Fe–S] cluster biogenesis have recently been found in plants, as well, and point to the existence of two distinct systems in these organisms, one located in plastids and one in mitochondria. Here we present the first biochemical confirmation of the activity of two components of the mitochondrial machinery in Arabidopsis, AtNFS1 and AtISU1. Analysis of the expression patterns of the corresponding genes, as well as AtISU2 and AtISU3, and the phenotypes of plants in which these genes are up or down-regulated are consistent with a role for the mitochondrial [Fe–S] assembly system in the maturation of proteins required for normal plant development.