Biology subjects

Ostersetzer, O.

Publications and source records attributed to Ostersetzer, O..

4 recordsLinked to original sources

bioRxiv2022

MSP1 encodes an essential RNA-binding PPR factor required for nad1 maturation and complex I biogenesis in Arabidopsis mitochondria

SummaryMitochondria are semi-autonomous organelles that serve as hubs for aerobic energy metabolism. The biogenesis of the respiratory (OXPHOS) system relies on nuclear-encoded factors, which regulate the transcription, processing and translation of mitochondrial (mt)RNAs. These include proteins of primordial origin, as well as eukaryotic-type RNA-binding families recruited from the host genomes to function in mitogenome expression. Pentatricopeptide repeat (PPR) proteins constitute a major gene-family in angiosperms that is pivotal in many aspects of mtRNA metabolism, such as editing, splicing or stability. Here, we report the analysis of MITOCHONDRIA STABILITY/PROCESSING PPR FACTOR1 (MSP1, At4g20090), a canonical mitochondria-localized PPR protein that is necessary for mitochondrial biogenesis and embryo-development. Functional complementation confirmed that the phenotypes result from a disruption of the MSP1 gene. As a loss-of-function allele of Arabidopsis MSP1 leads to seed abortion, we employed an embryo-rescue method for the molecular characterization of msp1 mutants. Our data show that msp1 embryo-development fails to proceed beyond the heart-torpedo transition stage as a consequence of a severe nad1 pre-RNA processing-defect, resulting in the loss of respiratory complex I (CI) activity. The maturation of nad1 involves the processing of three RNA-fragments, nad1.1, nad1.2 and nad1.3. Based on biochemical analyses and the mtRNA profiles in wild-type and msp1 plants, we concluded that through its association with a specific site in nad1.1, MSP1 facilitates the generation of its 3-terminus and stabilizes it -a prerequisite for nad1 exons a-b splicing. Our data substantiate the importance of mtRNA metabolism for the biogenesis of the respiratory machinery during early-plant development.

plant biology↗

bioRxiv2020

Insights into the mitochondrial transcriptome landscapes of two Brassicales plant species, Arabidopsis thaliana (var. Col-0) and Brassica oleracea (var. botrytis)

Mitochondria play key roles in cellular energy metabolism within eukaryotic cells. As relics of endosymbiotic bacteria, most (but not all) mitochondria contain their own genome (mitogenome, mtDNA), as well as intrinsic biosynthetic machinery for making organelle RNAs and proteins. The expression of the mtDNA requires regulated metabolism of its transcriptome by nuclear-encoded factors. Post-transcriptional mtRNA modifications play a central role in the expression of the plant mitogenomes, and hence in organellar biogenesis and plant physiology. Despite extensive investigations, a full map of angiosperm mitochondrial transcriptomes, a prerequisite for the elucidation of the basic RNA biology of mitochondria, has not been reported yet. Using RNA-seq data, RT-PCR and bioinformatics, we sought to explore the gene expression profiles of land plant mitochondria. Here, we present the mitochondrial transcriptomic maps of two key Brassicaceae species, Arabidopsis thaliana (var Col-0) and cauliflower (Brassica oleracea var. botrytis). The revised transcriptome landscapes of Arabidopsis and cauliflower mitogenomes provide with more detail into mtRNA biology and processing in angiosperm mitochondria, and we expect that they would serve as a valuable resource for the plant organellar community. Accession numbersSequences are available at the Sequence Read Archive (accession no. PRJNA472433), for both Arabidopsis thaliana var. Col-0 mtRNA (SRA no. SRX4110179) and Brassica oleracea var. botrytis mtRNA (SRA no. SRX4110177).

plant biology↗

bioRxiv2019

The unique topologies of N6-Adenosine methylation (m6A) in land-plant mitochondria and their putative effects on organellar gene-expression

Mitochondria are the main source of ATP production and also contribute to many other processes central to cellular function. Mitochondrial activities have been linked with growth, differentiation and aging. As relicts of bacterial endosymbionts, these organelles contain their own genetic system (i.e., mitogenome or mtDNA). The expression of the mtDNA in plants is complex, particularly at the posttranscriptional level. Following transcription, the polycistronic pre-RNAs in plant mitochondria are processed into individual RNAs, which then undergo extensive modifications, as trimming, splicing and C[->]U editing, before being translated by organellar ribosomes. Our study focuses on N6-methylation of Adenosine ribonucleotides (m6A-RNA) in plant mitochondria. m6A is the most common modification in eukaryotic mRNAs. The biological significance of this highly dynamic modification is under investigation, but its widely accepted that m6A mediates structural switches that affect RNA stability and activity. By performing m6A-pulldown/RNA-seq (m6A-RIP-seq) analyses of Arabidopsis and cauliflower mitochondrial transcripts (mtRNAs), we provide with detail information on the m6A landscapes in angiosperms mitochondria. The results indicate that m6A targets different types of mtRNAs, including coding sequences, UTRs, introns and non-coding RNA species. While introns and noncoding-RNAs undergo multiple m6A modifications along the transcript, in mRNAs m6A-modifications are preferably positioned near start-codons, and may modulate the translatability of the m6A-modified transcripts.

molecular biology↗

bioRxiv2019

The PPR-related splicing cofactor MSP1/EMB1025 protein, encoded by At4g20090, encode an essential protein that is required for the splicing of nad1 intron 1 and for the biogenesis of complex I in Arabidopsis mitochondria

Group II introns are particularly plentiful within plant mitochondrial genomes (mtDNAs), where they interrupt the coding-regions of many organellar genes, especialy within complex I (CI) subunits. Their splicing is essential for the biogenesis of the respiratory system and is facilitated by various protein-cofactors that belong to a diverse set of RNA-binding cofactors. These including maturases, which co-evolved with their host-introns, and various trans-acting factors, such as members of the pentatricopeptide-repeat (PPR) protein family. The genomes of angiosperms contain hundreds of PPR-related genes that are postulated to reside within the organelles and affect diverse posttranscriptional steps, such as editing, RNA-stability and processing or translation. Here, we report the characterization of MSP1 (Mitochondria Splicing PPR-factor 1; also denoted as EMB1025), which plays a key role in the processing of nad1 pre-RNAs in Arabidopsis mitochondria. Mutations in MSP1 gene-locus (At4g20090) result in early embryonic arrest. To analyze the putative roles of MSP1 in organellar RNA-metabolism we used a modified embryo-rescue method, which allowed us to obtain sufficient plant tissue for the analysis of the RNA and protein profiles associated with msp1 mutants. Our data indicate that MSP1 is essential for the trans-splicing of nad1 intron 1 in Arabidopsis mitochondria. Accordingly, msp1 mutants show CI biogenesis defects and reduced respiratory-mediated functions. These results provide with important insights into the roles of nuclear-encoded factors during early plant development, and contribute to our limited understanding of the importance of RNA-maturation and splicing in plant mitochondria during early embryogenesis.

plant biology↗