Chloroplast iron-sulfur cluster protein maturation requires the essential cysteine desulfurase CpNifS

Abstract

NifS-like proteins provide the sulfur (S) for the formation of iron-sulfur (Fe-S) clusters, an ancient and essential type of cofactor found in all three domains of life. Plants are known to contain two distinct NifS-like proteins, localized in the mitochondria (MtNifS) and the chloroplast (CpNifS). In the chloroplast, five different Fe-S cluster types are required in various proteins. These plastid Fe-S proteins are involved in a variety of biochemical pathways including photosynthetic electron transport and nitrogen and sulfur assimilation. In vitro, the chloroplastic cysteine desulfurase CpNifS can release elemental sulfur from cysteine for Fe-S cluster biogenesis in ferredoxin. However, because of the lack of a suitable mutant allele, the role of CpNifS has not been studied thus far in planta. To study the role of CpNifS in Fe-S cluster biogenesis in vivo, the gene was silenced by using an inducible RNAi (interference) approach. Plants with reduced CpNifS expression exhibited chlorosis, a disorganized chloroplast structure, and stunted growth and eventually became necrotic and died before seed set. Photosynthetic electron transport and carbon dioxide assimilation were severely impaired in the silenced plant lines. The silencing of CpNifS decreased the abundance of all chloroplastic Fe-S proteins tested, representing all five Fe-S cluster types. Mitochondrial Fe-S proteins and respiration were not affected, suggesting that mitochondrial and chloroplastic Fe-S assembly operate independently. These findings indicate that CpNifS is necessary for the maturation of all plastidic Fe-S proteins and, thus, essential for plant growth.Fe-S proteins ͉ inducible RNAi ͉ photosynthesis ͉ Arabidopsis thaliana

A Program for Iron Economy during Deficiency Targets Specific Fe Proteins

“…1, 3, and 4). RNAi lines induced for loss of NFS2 or SufBCD complex components had shown a general loss of all Fe-S proteins, including strong effects on PSI subunits PSAA, and PSAB on GOGAT (Van Hoewyk et al, 2007;Hu et al, 2017b). However, we did not see this general loss of plastid Fe-S cluster proteins for Fe deficiency.…”

“…Therefore, at least some of the observed effects seem to be caused by Fe deficiency proper and not just by downstream defects due to lack of cofactor assembly. We can also compare consequences of Fe deficiency at the molecular level with effects caused by genetically induced loss of Fe-S assembly factors NFS2 (Van Hoewyk et al, 2007) and SUF-BCD (Hu et al, 2017a(Hu et al, , 2017b. Loss via RNAi of NFS2 activity (Van Hoewyk et al, 2007) or SUF-BCD activity (Hu et al, 2017b) caused physiological effects after 1 week that are very similar to the Fe deficiency described here (Figs.…”

Vitamin B1 biosynthesis in plants requires the essential iron–sulfur cluster protein, THIC

“…In Arabidopsis, two distinct NifS proteins exist, localized to the chloroplast and mitochondria (CpNifS and MtNifS, respectively). Recently, a study employing a CpnifS mutant has shown that the protein is essential for the maturation of plastidic Fe-S proteins (35). As THIC is localized to the chloroplast, we examined both THIC abundance and thiamin content in the CpnifS mutant.…”

An Allelic Mutant Series of ATM3 Reveals Its Key Role in the Biogenesis of Cytosolic Iron-Sulfur Proteins in Arabidopsis

“…Plant cytosol contains homologs of the cytosolic Fe-S assembly proteins that have recently been identified in yeast (Lill and Mü hlenhoff, 2008), including the scaffold protein AtNBP35 (Bych et al, 2008;Kohbushi et al, 2009) and the hydrogenase-like AtNAR1 (Cavazza et al, 2008). It is thought that cytosolic Fe-S cluster assembly is dependent on at least one of the organelles, because the Cys desulfurases that generate sulfur for Fe-S clusters, CpNifS and NFS1, are strictly localized in the plastids and mitochondria, respectively (Kushnir et al, 2001;Frazzon et al, 2007;Van Hoewyk et al, 2007).…”