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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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Chloroplast editing is not recovered in light green leaves of oz1–1.RNA from yellow leaves and light green leaves of 8-week-old oz1–1 plants were used for RT-PCR and bulk sequencing. Portions of electrophoretograms are shown. Arrow indicates the position of editable C target.
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pgen.1005028.g006: Chloroplast editing is not recovered in light green leaves of oz1–1.RNA from yellow leaves and light green leaves of 8-week-old oz1–1 plants were used for RT-PCR and bulk sequencing. Portions of electrophoretograms are shown. Arrow indicates the position of editable C target.

Mentions: Although pigmentation has been partially recovered in light green leaves, plastid editing is still defective in those leaves compared to wild type Col (Fig. 6). No obvious difference in editing between yellow and green leaves was observed. This finding indicates that the defects in editing are not due to a pleiotropic effect caused by some other chloroplast developmental problem in yellow chlorophyll-deficient leaves. Green leaves were therefore used to prepare protoplasts. OZ1 was cloned into a pSAT4a vector to create 35S::OZ1, a plant transient expression vector driven by a 35S promoter for transfections of oz1–1 protoplasts. A chloroplast targeted YFP construct (35S::cpYFP) was included as a negative control. Monitoring of transfection efficiency of the YFP constructs by microscopy indicated expression of YFP in over 50% of the protoplasts.


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)

Chloroplast editing is not recovered in light green leaves of oz1–1.RNA from yellow leaves and light green leaves of 8-week-old oz1–1 plants were used for RT-PCR and bulk sequencing. Portions of electrophoretograms are shown. Arrow indicates the position of editable C target.
© Copyright Policy
Related In: Results  -  Collection

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

pgen.1005028.g006: Chloroplast editing is not recovered in light green leaves of oz1–1.RNA from yellow leaves and light green leaves of 8-week-old oz1–1 plants were used for RT-PCR and bulk sequencing. Portions of electrophoretograms are shown. Arrow indicates the position of editable C target.
Mentions: Although pigmentation has been partially recovered in light green leaves, plastid editing is still defective in those leaves compared to wild type Col (Fig. 6). No obvious difference in editing between yellow and green leaves was observed. This finding indicates that the defects in editing are not due to a pleiotropic effect caused by some other chloroplast developmental problem in yellow chlorophyll-deficient leaves. Green leaves were therefore used to prepare protoplasts. OZ1 was cloned into a pSAT4a vector to create 35S::OZ1, a plant transient expression vector driven by a 35S promoter for transfections of oz1–1 protoplasts. A chloroplast targeted YFP construct (35S::cpYFP) was included as a negative control. Monitoring of transfection efficiency of the YFP constructs by microscopy indicated expression of YFP in over 50% of the protoplasts.

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