Project description:Pentatricopeptide repeat (PPR) proteins are RNA binding proteins that function in posttranscriptional regulation as gene-specific regulators of RNA metabolism in plant organelles. Plant PPR proteins are divided into four classes: P, PLS, E and DYW. The E- and DYW-class proteins are mainly implicated in RNA editing, whereas most of the P-class proteins predominantly participate in RNA cleavage, splicing and stabilization. In contrast, the functions of PLS-class proteins still remain obscure. Here, we report the function of PLS-class PpPPR_31 and PpPPR_9 in Physcomitrella patens. The knockout (KO) mutants of PpPPR_31 and PpPPR_9 exhibited slower protonema growth compared to the wild type. The PpPPR_31 KO mutants showed a considerable reduction in the splicing of nad5 intron 3 and atp9 intron 1. The PpPPR_9 KO mutants displayed severely reduced splicing of cox1 intron 3. An RNA electrophoresis mobility shift assay showed that the recombinant PpPPR_31 protein bound to the 5' region of nad5 exon 4 and the bulged-A region in domain VI of atp9 group II intron 1 while the recombinant PpPPR_9 bound to the translated region of ORF622 in cox1 intron 3. These results suggest that PLS-class PPR proteins may influence the splicing efficiency of mitochondrial group II introns.
Project description:RNA editing, particularly cytidine-to-uridine conversions in plant organelles, plays a crucial role in regulating gene expression. While natural PLS-type PPR proteins are specialized in this process, synthetic PPR proteins offer significant potential for targeted RNA editing. In this study, we engineered chimeric editing factors by fusing synthetic P-type PPR guides with the DYW cytidine deaminase domain from a moss mitochondrial editing factor, PPR56. These designer PPR editors (dPPRe) were tested in Escherichia coli and Nicotiana benthamiana chloroplasts and mitochondria, demonstrating efficient and precise de novo RNA editing. Transcriptome-wide analysis of the most efficient chloroplastic dPPRe revealed minimal off-target effects, with only three non-target C sites edited due to sequence similarity with the intended target. This study introduces a novel and precise method for RNA base editing in plant organelles, paving the way for new approaches in gene regulation applicable to plants and potentially other organisms.
Project description:Chloroplast gene expression is controlled by numerous nuclear-encoded RNA-binding proteins. Among them, pentatricopeptide repeat (PPR) proteins are known to be a key player in posttranscriptional regulation in chloroplasts. However, the functions of many PPR proteins remain unknown. In this study, we characterized the function of a chloroplast-localized P-class PPR protein PpPPR_21 in Physcomitrella patens. Knockout (KO) mutants of PpPPR_21 exhibited a reduced growth of the protonemata and lower photosynthetic activity. Immuno-blot analysis and blue-native gel analysis showed a remarkable reduction of the photosystem II (PSII) reaction center protein and poorly formation of the PSII super-complexes in the KO mutants. To access whether PpPPR_21 is involved in the chloroplast gene expression, chloroplast genome-wide microarray analysis and northern blot hybridization were performed. These analyses indicated that the psbI-ycf12 transcript encoding the low molecular weight subunits of PSII, did not accumulate in the KO mutants while other psb transcripts accumulated at similar levels of WT and the KO mutants. A complemented PpPPR_21 KO moss transformed with the cognate full-length PpPPR_21 cDNA rescued the psbI transcript accumulation level. RNA binding experiments showed that the recombinant PpPPR_21 bound efficiently to the 5’-untraslated and translated region of the psbI mRNA. The present study suggests that PpPPR_21 may be essential for accumulation of a stable psbI-ycf12 mRNA.
Project description:Chloroplast function requires the coordinated action of nuclear- and chloroplast-derived proteins, including several hundred nuclear-encoded pentatricopeptide repeat (PPR) proteins that regulate plastid mRNA metabolism. Despite their large number and importance, regulatory mechanisms controlling PPR expression are poorly understood. Here we show that the Arabidopsis NOT4A ubiquitin-ligase positively regulates the expression of PROTON GRADIENT REGULATION 3 (PGR3), a PPR protein required for translating several thylakoid-localised photosynthetic components and ribosome subunits within chloroplasts. Loss of NOT4A function leads to a strong depletion of cytochrome b6f and NDH complexes, as well plastid 30S ribosomes, which reduces mRNA translation and negatively impacts photosynthetic capacity, causing pale-yellow and slow-growth phenotypes. Quantitative transcriptome and proteome analyses reveal that PGR3 is misregulated in not4a. We show that the molecular not4a defects mimic those of a pgr3 mutant, and that normal plastid function is restored through transgenic PGR3 expression. Our work identifies NOT4A as crucial for ensuring robust photosynthetic function during development and stress-response, through promoting PGR3 production and chloroplast translation.
Project description:Chloroplast function requires the coordinated action of nuclear- and chloroplast-derived proteins, including several hundred nuclear-encoded pentatricopeptide repeat (PPR) proteins that regulate plastid mRNA metabolism. Despite their large number and importance, regulatory mechanisms controlling PPR expression are poorly understood. Here we show that the Arabidopsis NOT4A ubiquitin-ligase positively regulates PROTON GRADIENT 3 (PGR3), a PPR protein required for translating 30S ribosome subunits and several thylakoid-localised photosynthetic components within chloroplasts.
Project description:Pentatricopeptide repeat (PPR) proteins, which are characterized by tandem 30-40 amino acid sequence motifs, constitute a large gene family in plants. These known PPR proteins have been identified to play important roles in organellar RNA metabolism and plant development in Arabidopsis and rice. However, functions of PPR genes in woody species remain still largely unknown. Here, we identified and characterized a total of 626 PPR genes containing PPR motifs in the poplar genome. A comprehensive genome-wide analysis of the poplar PPR gene family was performed, including chromosomal location, phylogenetic relationships, gene duplication. Transcriptomic analyses identified that 154 of the PtrPPR genes were induced by biotic and abiotic treatments, including Marssonina brunnea, salicylic acid (SA), methyl jasmonate (MeJA), wounding, cold and salinity. Quantitative RT-PCR analysis further confirmed the expression profiles of 11 PtrPPR genes under different stresses. Our results contribute to a more comprehensive understanding the roles of PPR proteins and provided an insight for improving the stress tolerance in poplar.
Project description:A transcription factor CYTOKININ-RESPONSIVE GATA FACTOR 1 (CGA1) regulates chloroplast development in rice (Oryza sativa) through modifying the expression of important nuclear expressed, chloroplast localized genes. A transcriptome analysis was done in wild type plants and transgenic rice over-expressing this OsCGA1 to identify the set of genes with altered expression.
Project description:A transcription factor CYTOKININ-RESPONSIVE GATA FACTOR 1 (CGA1) regulates chloroplast development in rice (Oryza sativa) through modifying the expression of important nuclear expressed, chloroplast localized genes. A transcriptome analysis was done in wild type plants and transgenic rice over-expressing this OsCGA1 to identify the set of genes with altered expression. RNA was extracted from leaves of 4-wk old wild type and OsCGA1 overexpressing rice plants and hybridized to Affymetrix Rice Genome Array. Three biological replicates were sampled for wild type and OX plants.
Project description:Transcription factors encoded by GLK genes are putative positive regulators of chloroplast development. To identify the potential downstream genes regulated by OsGLK1, we performed the rice 44k oligo microarray analysis. Keywords: over-expression of full-length cDNAs
Project description:The rice genome encodes 18 HDACs from the three different families. The RPD3 family comprises 14 genes, the HDT and the Sir families contain each 2 genes. Previous studies showed that rice RPD3 members are involved in various developmental processes. In this work, we used quantitative proteomics to investigate the acetylomes regulated by rice rpd3 family HDAC proteins in seedlings. Our results establish an unprecedentedly comprehensive protein acetylome in plants and reveal that HDA714 is a major deacetylase targeting a large number of Kac sites on hundreds of proteins of diverse function. We show that HDA714-dependent deacetylation is required for glycolytic activity, ribosome translational function, and plant growth and development. Our data uncovers novel regulators of protein Kac homeostasis in plants and extends the role of protein Kac in gene expression to translational regulation.