title: C-Terminal Region of Sulfite Reductase Is Important to Localize to Chloroplast Nucleoids in Land Plants.
abstract: Chloroplast (cp) DNA is compacted into cpDNA-protein complexes, called cp nucleoids. An abundant and extensively studied component of cp nucleoids is the bifunctional protein sulfite reductase (SiR). The preconceived role of SiR as the core cp nucleoid protein, however, is becoming less likely because of the recent findings that SiRs do not associate with cp nucleoids in some plant species, such as Zea mays and Arabidopsis thaliana To address this discrepancy, we have performed a detailed phylogenetic analysis of SiRs, which shows that cp nucleoid-type SiRs share conserved C-terminally encoded peptides (CEPs). The CEPs are likely to form a bacterial ribbon-helix-helix DNA-binding motif, implying a potential role in attaching SiRs onto cp nucleoids. A proof-of-concept experiment was conducted by fusing the nonnucleoid-type SiR from A. thaliana (AtSiR) with the CEP from the cp nucleoid-type SiR of Phaseolus vulgaris The addition of the CEP drastically altered the intra-cp localization of AtSiR to cp nucleoids. Our analysis supports the possible functions of CEPs in determining the localization of SiRs to cp nucleoids and illuminates a possible evolutionary scenario for SiR as a cp nucleoid protein.
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Japan.
authors.forename: Takuto
authors.initials: T
authors.lastname: Otani
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Ishibashi
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Japan yoshiki@pmg.bot.kyoto-u.ac.jp.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nishimura
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D002736:Chloroplasts / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics*; D046911:Macromolecular Substances; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics*; D010455:Peptides / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D003313:Zea mays / Q000235:genetics
chemical_list: D018742:DNA, Chloroplast; D046911:Macromolecular Substances; D010455:Peptides; D010940:Plant Proteins; D050862:Oxidoreductases Acting on Sulfur Group Donors
keywords: evolution; nucleoid; sulfite reductase