Functional relationships of three NFU proteins in the biogenesis of chloroplastic iron‐sulfur clusters

Abstract

Iron‐sulfur clusters are required in a variety of biological processes. Biogenesis of iron‐sulfur clusters includes assembly of iron‐sulfur clusters on scaffold complexes and transfer of iron‐sulfur clusters to recipient apoproteins by iron‐sulfur carriers, such as nitrogen‐fixation‐subunit‐U (NFU)‐type proteins. Arabidopsis thaliana has three plastid‐targeted NFUs: NFU1, NFU2, and NFU3. We previously discovered that nfu2−/− nfu3−/− mutants are embryo lethal. The lack of viable nfu2−/− nfu3−/− mutants posed a serious challenge. To overcome this problem, we characterized nfu2‐1−/− nfu3‐2+/‐ and nfu2‐1+/‐ nfu3‐2−/− sesquimutants. Simultaneous loss‐of‐function mutations in NFU2 and NFU3 have an additive effect on the declines of 4Fe‐4S‐containing PSI core subunits. Consequently, the sesquimutants had much lower PSI and PSII activities, much less chlorophyll, and much smaller plant sizes, than nfu2‐1 and nfu3‐2 single mutants. These observations are consistent with proposed roles of NFU3 and NFU2 in the biogenesis of chloroplastic 4Fe‐4S. By performing spectroscopic and in vitro reconstitution experiments, we found that NFU1 may act as a carrier for chloroplastic 4Fe‐4S and 3Fe‐4S clusters. In line with this hypothesis, loss‐of‐function mutations in NFU1 resulted in significant declines in 4Fe‐4S‐ and 3Fe‐4S‐containing chloroplastic proteins. The declines of PSI activity and 4Fe‐4S‐containing PSI core subunits in nfu1 mutants indicate that PSI is the main target of NFU1 action. The reductions in 4Fe‐4S‐containing PSI core proteins and PSI activity in nfu3‐2, nfu2‐1, and nfu1 single mutants suggest that all three plastid‐targeted NFU proteins contribute to the biogenesis of chloroplastic 4Fe‐4S clusters. Although different insertion sites of T‐DNA lines may cause variations in phenotypic results, mutation severity could be an indicator of the relative importance of the gene product. Our results are consistent with the hypothesis that NFU3 contributes more than NFU2 and NFU2 contributes more than NFU1 to the production of 4Fe‐4S‐containing PSI core subunits.

The Geomagnetic Field (GMF) Is Required for Lima Bean Photosynthesis and Reactive Oxygen Species Production

“…Plastids, which are a major subcellular sink of iron and Fe-S clusters, are pivotal to photosynthesis in the electron transport (ET) chain [28]. Examples of chloroplastic Fe-S proteins include 2Fe-2Scontaining chloroplast ferredoxin, 3Fe-4S-containing ferredoxin-glutamine oxoglutarate aminotransferase and 4Fe-4S-containing Photosystem I core proteins PsaA, PsaB, and PsaC ( [29] and references therein). MF-stimulating effects have been described in regard to the evolution of a RP appearing in both photosystems I and II (PSI, PSII) [30,31] and were explained by a hypothesis of RP recombination in reaction centers [32].…”

Characterization of the metabolic networks and gene-metabolite associations underlying cuticle production in maize via systems’ biology approaches

“…S5. Abbreviation of organ name: Coleo, coleoptiles; Enc_lf, encase leaves Kim et al, 2019a;3) Kim et al, 2017b;; 4) 5) Qiao et al, 2020;6) Sheehan et al, 2007;7) Kobayashi et al, 2014;Yeh et al, 2021;8) Rocha et al, 2018;Fujii et al, 2019;9) Schwenkert et al, 2010;Meguro et al, 2011;Wang et al, 2012;Reumann, 2013;Schlicke et al, 2014;Kim et al, 2015;Kobayashi and Masuda, 2016;Pattanayak and Tripathy, 2016;Kim et al, 2017a;Herbst et al, 2018;Dmitrieva et al, 2021;Satyanarayan et al, 2021;10)…”

“…In addition, we have also identified candidates involved in photosynthesis-related coenzyme metabolism, including chlorophyll biosynthesis (CHLH1, CRD1, DVR1, GSA2, YCF54) (Wang et al, 2012;Schlicke et al, 2014;Kobayashi and Masuda, 2016;Pattanayak and Tripathy, 2016;Herbst et al, 2018), conversion between chlorophyll a and chlorophyll b (CHAO2 and HCAR) (Meguro et al, 2011;Dmitrieva et al, 2021), plastoquinone biosynthesis (AAE14, APG1, and SPS2) (Reumann, 2013;Kim et al, 2015b;Kim et al, 2017a), and chloroplastic electron transfer (HCF101 and NFU1) (Schwenkert et al, 2010;Satyanarayan et al, 2021).…”