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The PPR-SMR protein PPR53 enhances the stability and translation of specific chloroplast RNAs in maize.

ABSTRACT: Pentatricopeptide repeat (PPR) proteins are helical repeat proteins that bind RNA and influence gene expression in mitochondria and chloroplasts. Several PPR proteins in plants harbor a carboxy-terminal small-MutS-related (SMR) domain, but the functions of the SMR appendage are unknown. To address this issue, we studied a maize PPR-SMR protein denoted PPR53 (GRMZM2G438524), which is orthologous to the Arabidopsis protein SOT1 (AT5G46580). Null ppr53 alleles condition a chlorotic, seedling-lethal phenotype and a reduction in plastid ribosome content. Plastome-wide transcriptome and translatome analyses revealed strong defects in the expression of the ndhA and rrn23 genes, which were superimposed on secondary effects resulting from a decrease in plastid ribosome content. Transcripts with processed 5'-ends mapping approximately 70 nucleotides upstream of rrn23 and ndhA are absent in ppr53 mutants, and the translational efficiency of the residual ndhA mRNAs is reduced. Recombinant PPR53 binds with high affinity and specificity to the 5' proximal region of the PPR53-dependent 23S rRNA, suggesting that PPR53 protects this RNA via a barrier mechanism similar to that described for several PPR proteins lacking SMR motifs. However, recombinant PPR53 did not bind with high affinity to the ndhA 5' untranslated region, suggesting that PPR53's RNA-stabilization and translation-enhancing effects at the ndhA locus involve the participation of other factors.

SUBMITTER: Zoschke R

PROVIDER: S-EPMC4777676 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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The PPR-SMR protein PPR53 enhances the stability and translation of specific chloroplast RNAs in maize.

Zoschke Reimo R Watkins Kenneth P KP Miranda Rafael G RG Barkan Alice A

The Plant journal : for cell and molecular biology 20160205 5

Pentatricopeptide repeat (PPR) proteins are helical repeat proteins that bind RNA and influence gene expression in mitochondria and chloroplasts. Several PPR proteins in plants harbor a carboxy-terminal small-MutS-related (SMR) domain, but the functions of the SMR appendage are unknown. To address this issue, we studied a maize PPR-SMR protein denoted PPR53 (GRMZM2G438524), which is orthologous to the Arabidopsis protein SOT1 (AT5G46580). Null ppr53 alleles condition a chlorotic, seedling-lethal ...[more]

PMID: 26643268

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Project description:Chloroplast genomes in land plants contain approximately 100 genes, the majority of which reside in polycistronic transcription units derived from cyanobacterial operons. The expression of chloroplast genes is integrated into developmental programs underlying the differentiation of photosynthetic cells from non-photosynthetic progenitors. In C4 plants, the partitioning of photosynthesis between two cell types, bundle sheath and mesophyll, adds an additional layer of complexity. We used ribosome profiling and RNA-seq to generate a comprehensive description of chloroplast gene expression at four stages of chloroplast differentiation, as displayed along the maize seedling leaf blade. The rate of protein output of most genes increases early in development and declines once the photosynthetic apparatus is mature. The developmental dynamics of protein output fall into several patterns. Programmed changes in mRNA abundance make a strong contribution to the developmental shifts in protein output, but output is further adjusted by changes in translational efficiency. RNAs with prioritized translation early in development are largely involved in chloroplast gene expression, whereas those with prioritized translation in photosynthetic tissues are generally involved in photosynthesis. Differential gene expression in bundle sheath and mesophyll chloroplasts results primarily from differences in mRNA abundance, but differences in translational efficiency amplify mRNA-level effects in some instances. In most cases, rates of protein output approximate steady-state protein stoichiometries, implying a limited role for proteolysis in eliminating unassembled or damaged proteins under non-stress conditions. Tuned protein output results from gene-specific trade-offs between translational efficiency and mRNA abundance, both of which span a large dynamic range. Analysis of ribosome footprints at sites of RNA editing showed that the chloroplast translation machinery does not generally discriminate between edited and unedited RNAs. However, editing of ACG to AUG at the rpl2 start codon is essential for translation initiation, demonstrating that ACG does not serve as a start codon in maize chloroplasts.

Dataset Information

The PPR-SMR protein PPR53 enhances the stability and translation of specific chloroplast RNAs in maize.

Publications

The PPR-SMR protein PPR53 enhances the stability and translation of specific chloroplast RNAs in maize.

Similar Datasets

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