Molecular scaffold for [Fe-S] cluster assembly of chloroplastic iron-sulfur proteins. Required for biogenesis of ferredoxin, a major photosynthetic electron carrier containing [2Fe-2S] cluster. Required for the assembly of photosystem I complex. Binds 1 [2Fe-2S] cluster per subunit. Homodimer; disulfide-linked. Predominantly expressed in leaves and floral stalks. Ubiquitous (at protein level). Plants are dwarf with faint pale-green leaves, decreased amount of ferredoxin and impaired photosystem I accumulation. May be due to a competing donor splice site. Belongs to the NifU family. The predicted gene At5g49940 has been split into 2 genes: At5g49940 and At5g49945.