Requirements of the cytosolic iron–sulfur cluster assembly pathway in Arabidopsis

Abstract

The assembly of iron–sulfur (Fe–S) clusters requires dedicated protein factors inside the living cell. Striking similarities between prokaryotic and eukaryotic assembly proteins suggest that plant cells inherited two different pathways through endosymbiosis: the ISC pathway in mitochondria and the SUF pathway in plastids. Fe–S proteins are also found in the cytosol and nucleus, but little is known about how they are assembled in plant cells. Here, we show that neither plastid assembly proteins nor the cytosolic cysteine desulfurase ABA3 are required for the activity of cytosolic aconitase, which depends on a [4Fe–4S] cluster. In contrast, cytosolic aconitase activity depended on the mitochondrial cysteine desulfurase NFS1 and the mitochondrial transporter ATM3. In addition, we were able to complement a yeast mutant in the cytosolic Fe–S cluster assembly pathway, dre2 , with the Arabidopsis homologue AtDRE2 , but only when expressed together with the diflavin reductase AtTAH18 . Spectroscopic characterization showed that purified AtDRE2 could bind up to two Fe–S clusters. Purified AtTAH18 bound one flavin per molecule and was able to accept electrons from NAD(P)H. These results suggest that the proteins involved in cytosolic Fe–S cluster assembly are highly conserved, and that dependence on the mitochondria arose before the second endosymbiosis event leading to plastids.

Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway

“…The CIA pathway is responsible for providing Fe-S clusters to respective apoproteins in the cytosol and the nucleus (Bernard et al, 2013). In the current model, electrons provided by NADPH oxidation are transferred by Top1T722A MUTANT HYPERSENSITIVE and DEREPRESSED FOR RIBOSOMAL PROTEIN S14 EXPRESSION (DRE2) to the scaffold protein NUCLEOTIDE BINDING PROTEIN35.…”

Epigenetic role for the conserved Fe-S cluster biogenesis protein AtDRE2 in Arabidopsis thaliana

“…DME governs DNA demethylation in the central cell and is Fe-S dependent, as discussed above. AtDRE2 regulates the same process and is also known to bind Fe-S clusters (6). To establish whether the CIA pathway might influence DME and AtDRE2 activities, we analyzed three hallmarks of the dme phenotype in mutants of the following CIA proteins: AtATR3, the binding partner of AtDRE2; the scaffold protein AtNBP35; AtNAR1; and the CIA targeting complex protein CIA1.…”

“…The key genes involved in Fe-S biogenesis have been identified in bacteria and yeast and are highly conserved and essential in eukaryotes. The diflavin reductase Tah18 and Derepressed for Ribosomal protein S14 Expression 2 (Dre2) form a short electron transfer chain; their interaction is essential in organisms from yeast to plants (orthologs in Arabidopsis thaliana: AtATR3 and AtDRE2, respectively) to mammals (4)(5)(6). The soluble P-loop NTPases Cfd1 and Nbp35 form a scaffold complex, present in plants as an Nbp35 homodimer (7), which transfers Fe-S clusters to Nar1, a protein with sequence similarity to iron dehydrogenases (8).…”

Emerging links between iron-sulfur clusters and 5-methylcytosine base excision repair in plants

“…Role of AtDRE2 and AtNAR1 in gametes and seed development Most CIA proteins are required for early embryo development in Arabidopsis (Bych et al, 2008;Luo et al, 2012;Bernard et al, 2013;Nakamura et al, 2013;Buzas et al, 2014) and this function is zygotic (Nakamura et al, 2013;Buzas et al, 2014). In addition, mutations in AtDRE2 and AtNAR1 were identified in the pFWA-GFP screen (Nakamura et al, 2013;Buzas et al, 2014).…”