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A zinc finger motif-containing protein is essential for chloroplast RNA editing.

Sun T, Shi X, Friso G, Van Wijk K, Bentolila S, Hanson MR - PLoS Genet. (2015)

Bottom Line: Members of two additional gene families, the RIP/MORF and ORRM families, have each been found to be required for editing of particular sets of Cs in mitochondria and/or chloroplasts.The organelle zinc finger editing factor family (OZ) contains 4 members in Arabidopsis, three that are predicted to be targeted to chloroplasts and one to mitochondria.With the identification of OZ1, there are now 4 nuclear-encoded protein families known to be essential for plant organelle RNA editing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.

ABSTRACT
C-to-U editing of transcripts in plant organelles is carried out by small (<400 kD) protein complexes called editosomes. Recognition of the proper C target for editing is mediated by pentatricopeptide repeat (PPR) containing proteins that recognize cis-elements. Members of two additional gene families, the RIP/MORF and ORRM families, have each been found to be required for editing of particular sets of Cs in mitochondria and/or chloroplasts. By co-immunoprecipitation of the chloroplast editing factor ORRM1, followed by mass spectrometry, we have now identified a member of the RanBP2 type zinc fingers (pFAM00641) protein family that is required for editing of 14 sites in chloroplasts and affects editing efficiency of another 16 chloroplast C targets. In yeast two-hybrid assays, OZ1 (Organelle Zinc finger 1) interacts with PPR site recognition factors whose cognate sites are affected when OZ1 is mutated. No interaction of OZ1 with the chloroplast editing factors RIP2 and RIP9 was detected; however, OZ1 interacts with ORRM1, which binds to RIP proteins, allowing us to build a model for the chloroplast RNA editosome. The RNA editosomes that act upon most chloroplast C targets are likely to contain a PPR protein recognition factor, either RIP2 or RIP9, ORRM1, and OZ1. The organelle zinc finger editing factor family (OZ) contains 4 members in Arabidopsis, three that are predicted to be targeted to chloroplasts and one to mitochondria. With the identification of OZ1, there are now 4 nuclear-encoded protein families known to be essential for plant organelle RNA editing.

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OZ1 (At5g17790) gene structure and mutant phenotype.(A) Gene structure of OZ1. Triangle indicates the location of the T-DNA. Dashed box indicates the gene specific region selected for VIGS (Virus Induced Gene Silencing). (B-D) oz1–1 phenotype. (B) plants grown on MS media for 4 weeks. Left, wild type sibling, right, homozygous oz1 mutant. (C) new leaves turned light green on a six week old oz1 mutant. (D), eight week old oz1–1 (left) grows in soil compared to wild type (right).
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pgen.1005028.g003: OZ1 (At5g17790) gene structure and mutant phenotype.(A) Gene structure of OZ1. Triangle indicates the location of the T-DNA. Dashed box indicates the gene specific region selected for VIGS (Virus Induced Gene Silencing). (B-D) oz1–1 phenotype. (B) plants grown on MS media for 4 weeks. Left, wild type sibling, right, homozygous oz1 mutant. (C) new leaves turned light green on a six week old oz1 mutant. (D), eight week old oz1–1 (left) grows in soil compared to wild type (right).

Mentions: At5g17790 contains two tandem C2X10C2 zinc finger domains [28] called RanBP2 type zinc fingers (X2GDWICX2CX3NFARRX2CXRCX2-PRPEX2; pFAM00641), which were characterized in the Ran Binding Protein 2 (RanBP2). Ran is a small GTPase and RanBP2 is a nucleoporin that binds Ran via the zinc finger motifs. This gene previously was identified as mutated in a variegated Ds insertional mutant of Arabidopsis thaliana Landsberg erecta, but the cause of the chloroplast developmental aberration was not determined [28]. We obtained one T-DNA insertional line in A. thaliana ecotype Columbia from ABRC, SAIL_358_H03 (Fig. 3A). In contrast to the mutant in the Landsberg ecotype, the homozygous Columbia mutant showed a uniform yellow phenotype as a young seedling, as shown in Fig. 3B. Subsequent growth on sucrose media result in the appearance of light green, non-variegated leaves (Fig. 3C). These older mutant seedlings could be transferred to soil, where the pale green leaves were able to support autotrophic growth (Fig. 3D). The protein encoded by At5g17790 was given the name OZ1 (Organelle Zinc finger 1).


A zinc finger motif-containing protein is essential for chloroplast RNA editing.

Sun T, Shi X, Friso G, Van Wijk K, Bentolila S, Hanson MR - PLoS Genet. (2015)

OZ1 (At5g17790) gene structure and mutant phenotype.(A) Gene structure of OZ1. Triangle indicates the location of the T-DNA. Dashed box indicates the gene specific region selected for VIGS (Virus Induced Gene Silencing). (B-D) oz1–1 phenotype. (B) plants grown on MS media for 4 weeks. Left, wild type sibling, right, homozygous oz1 mutant. (C) new leaves turned light green on a six week old oz1 mutant. (D), eight week old oz1–1 (left) grows in soil compared to wild type (right).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4359148&req=5

pgen.1005028.g003: OZ1 (At5g17790) gene structure and mutant phenotype.(A) Gene structure of OZ1. Triangle indicates the location of the T-DNA. Dashed box indicates the gene specific region selected for VIGS (Virus Induced Gene Silencing). (B-D) oz1–1 phenotype. (B) plants grown on MS media for 4 weeks. Left, wild type sibling, right, homozygous oz1 mutant. (C) new leaves turned light green on a six week old oz1 mutant. (D), eight week old oz1–1 (left) grows in soil compared to wild type (right).
Mentions: At5g17790 contains two tandem C2X10C2 zinc finger domains [28] called RanBP2 type zinc fingers (X2GDWICX2CX3NFARRX2CXRCX2-PRPEX2; pFAM00641), which were characterized in the Ran Binding Protein 2 (RanBP2). Ran is a small GTPase and RanBP2 is a nucleoporin that binds Ran via the zinc finger motifs. This gene previously was identified as mutated in a variegated Ds insertional mutant of Arabidopsis thaliana Landsberg erecta, but the cause of the chloroplast developmental aberration was not determined [28]. We obtained one T-DNA insertional line in A. thaliana ecotype Columbia from ABRC, SAIL_358_H03 (Fig. 3A). In contrast to the mutant in the Landsberg ecotype, the homozygous Columbia mutant showed a uniform yellow phenotype as a young seedling, as shown in Fig. 3B. Subsequent growth on sucrose media result in the appearance of light green, non-variegated leaves (Fig. 3C). These older mutant seedlings could be transferred to soil, where the pale green leaves were able to support autotrophic growth (Fig. 3D). The protein encoded by At5g17790 was given the name OZ1 (Organelle Zinc finger 1).

Bottom Line: Members of two additional gene families, the RIP/MORF and ORRM families, have each been found to be required for editing of particular sets of Cs in mitochondria and/or chloroplasts.The organelle zinc finger editing factor family (OZ) contains 4 members in Arabidopsis, three that are predicted to be targeted to chloroplasts and one to mitochondria.With the identification of OZ1, there are now 4 nuclear-encoded protein families known to be essential for plant organelle RNA editing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America.

ABSTRACT
C-to-U editing of transcripts in plant organelles is carried out by small (<400 kD) protein complexes called editosomes. Recognition of the proper C target for editing is mediated by pentatricopeptide repeat (PPR) containing proteins that recognize cis-elements. Members of two additional gene families, the RIP/MORF and ORRM families, have each been found to be required for editing of particular sets of Cs in mitochondria and/or chloroplasts. By co-immunoprecipitation of the chloroplast editing factor ORRM1, followed by mass spectrometry, we have now identified a member of the RanBP2 type zinc fingers (pFAM00641) protein family that is required for editing of 14 sites in chloroplasts and affects editing efficiency of another 16 chloroplast C targets. In yeast two-hybrid assays, OZ1 (Organelle Zinc finger 1) interacts with PPR site recognition factors whose cognate sites are affected when OZ1 is mutated. No interaction of OZ1 with the chloroplast editing factors RIP2 and RIP9 was detected; however, OZ1 interacts with ORRM1, which binds to RIP proteins, allowing us to build a model for the chloroplast RNA editosome. The RNA editosomes that act upon most chloroplast C targets are likely to contain a PPR protein recognition factor, either RIP2 or RIP9, ORRM1, and OZ1. The organelle zinc finger editing factor family (OZ) contains 4 members in Arabidopsis, three that are predicted to be targeted to chloroplasts and one to mitochondria. With the identification of OZ1, there are now 4 nuclear-encoded protein families known to be essential for plant organelle RNA editing.

Show MeSH
Related in: MedlinePlus