title: OsNOA1/RIF1 is a functional homolog of AtNOA1/RIF1: implication for a highly conserved plant cGTPase essential for chloroplast function.
abstract: *The bacterial protein YqeH is a circularly permuted GTPase with homologs encoded by plant nuclear genomes. The rice homolog OsNOA1/RIF1 is encoded by the single-copy gene Os02g01440. OsNOA1/RIF1 is expressed in different tissues and is light-inducible. The OsNOA1/RIF1-EYFP fusion protein was targeted to chloroplasts in transgenic Arabidopsis plants. In addition, the rice homolog was able to rescue most of the growth phenotypes in an Arabidopsis rif1 mutant. *Rice (Oryza sativa) OsNOA1/RIF1 RNAi mutant seedlings were chlorotic with reduced pigment contents and lower photosystem II (PSII) efficiency. However, the expressions of the chloroplast-encoded genes rbcL, atpB, psaA and psbA were not affected. By contrast, reduced abundance of the chloroplast 16S rRNA was observed in the mutant. *Quantitative iTRAQ-LC-MS/MS proteomics investigations revealed proteome changes in the rice mutant consistent with the expected functional role of OsNOA1/RIF1 in chloroplast translation. The RNAi mutant showed significantly decreased expression levels of chloroplast-encoded proteins as well as nuclear-encoded components of chloroplast enzyme complexes. Conversely, upregulation of some classes of nonchloroplastic proteins, such as glycolytic and phenylpropanoid pathway enzymes, was detected. *Our work provides independent indications that a highly conserved nuclear-encoded cGTPase of likely prokaryotic origin is essential for proper chloroplast ribosome assembly and/or translation in plants.
authors.affiliation: Crop Molecular Breeding Center, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, China.|School of Biological Sciences.
authors.forename: Hongjia
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Edward
authors.initials: E
authors.lastname: Lau
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Maggie P Y
authors.initials: MPY
authors.lastname: Lam
authors.affiliation: School of Biological Sciences.
authors.forename: Hung
authors.initials: H
authors.lastname: Chu
authors.affiliation: Crop Molecular Breeding Center, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, China.
authors.forename: Sujuan
authors.initials: S
authors.lastname: Li
authors.affiliation: Crop Molecular Breeding Center, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, China.
authors.forename: Guo
authors.initials: G
authors.lastname: Huang
authors.affiliation: Crop Molecular Breeding Center, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Guo
authors.affiliation: Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Junqi
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
authors.forename: Ivan K
authors.initials: IK
authors.lastname: Chu
authors.affiliation: School of Biological Sciences.
authors.forename: Clive
authors.initials: C
authors.lastname: Lo
authors.affiliation: Crop Molecular Breeding Center, Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang, China.
authors.forename: Yuezhi
authors.initials: Y
authors.lastname: Tao
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry*; D002736:Chloroplasts / Q000201:enzymology*; D017124:Conserved Sequence / Q000235:genetics*; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005838:Genotype; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019001:Nitric Oxide Synthase / Q000737:chemistry*; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C521947:NOA1 protein, Arabidopsis; D019001:Nitric Oxide Synthase; D020558:GTP Phosphohydrolases
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