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Molecular and Cellular Biology, September 2008, p. 5337-5347, Vol. 28, No. 17
0270-7306/08/$08.00+0     doi:10.1128/MCB.00563-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Pentatricopeptide Repeat Protein PPR5 Stabilizes a Specific tRNA Precursor in Maize Chloroplasts ^,

Susanne Beick,^1, Christian Schmitz-Linneweber,^1,* Rosalind Williams-Carrier,² Bryan Jensen,² and Alice Barkan²

Molekulare Genetik, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany,¹ Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403²

Received 8 April 2008/ Returned for modification 12 June 2008/ Accepted 18 June 2008

Genes for pentatricopeptide repeat (PPR) proteins are found in all eukaryotic genomes analyzed but are particularly abundant in land plants. The majority of analyzed PPR proteins play a role in the processing or translation of organellar RNAs. Few PPR proteins have been studied in detail, and the functional repertoire and mechanisms of action of proteins in the PPR family are poorly understood. Here we analyzed a maize ortholog of the embryo-essential Arabidopsis thaliana gene AtPPR5. A genome-wide analysis of chloroplast RNAs that coimmunoprecipitate with Zea mays PPR5 (ZmPPR5) demonstrated that ZmPPR5 is bound in vivo to the unspliced precursor of trnG-UCC. Null and hypomorphic Zmppr5 insertion mutants are embryo viable but are deficient for chloroplast ribosomes and die as seedlings. These mutants show a dramatic decrease in both spliced and unspliced trnG-UCC RNAs, while the transcription of trnG-UCC is unaffected. These results, together with biochemical data documenting the sequence-specific binding of recombinant PPR5 to the trnG-UCC group II intron, suggest that PPR5 stabilizes the trnG-UCC precursor by directly binding and protecting an endonuclease-sensitive site. These findings add to the evidence that chloroplast-localized PPR proteins that are embryo essential in Arabidopsis typically function in the biogenesis of the plastid translation machinery.

Published ahead of print on 30 June 2008.

Supplemental data for this article may be found at http://mcb.asm.org/.

These authors contributed equally to this work.

This article has been cited by other articles:

• Williams-Carrier, R., Kroeger, T., Barkan, A. (2008). Sequence-specific binding of a chloroplast pentatricopeptide repeat protein to its native group II intron ligand. RNA 14: 1930-1941 [Abstract] [Full Text]