Project description:Chloroplasts are organelles responsible for photosynthesis. They originated form a procaryotic ancestor in the process of endosymbiosis and contain their own genomes. The chloroplast genome is packaged into a chromatin-like structure known as the nucleoid. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging and connection of the nucleoid structure to gene expression remain poorly understood. We show that Arabidopsis thaliana chloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. Membrane association of specific DNA regions is correlated with high levels of transcription, high protein occupancy and reduced DNA accessibility. Genes with low levels of transcription are further away from the membranes, have lower protein occupancy and higher DNA accessibility. Gene-specific disruption of transcription in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active Periphery.
Project description:Chloroplasts are organelles responsible for photosynthesis. They originated form a procaryotic ancestor in the process of endosymbiosis and contain their own genomes. The chloroplast genome is packaged into a chromatin-like structure known as the nucleoid. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging and connection of the nucleoid structure to gene expression remain poorly understood. We show that Arabidopsis thaliana chloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. Membrane association of specific DNA regions is correlated with high levels of transcription, high protein occupancy and reduced DNA accessibility. Genes with low levels of transcription are further away from the membranes, have lower protein occupancy and higher DNA accessibility. Gene-specific disruption of transcription in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active Periphery.
Project description:Chloroplasts are organelles responsible for photosynthesis. They originated form a procaryotic ancestor in the process of endosymbiosis and contain their own genomes. The chloroplast genome is packaged into a chromatin-like structure known as the nucleoid. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging and connection of the nucleoid structure to gene expression remain poorly understood. We show that Arabidopsis thaliana chloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. Membrane association of specific DNA regions is correlated with high levels of transcription, high protein occupancy and reduced DNA accessibility. Genes with low levels of transcription are further away from the membranes, have lower protein occupancy and higher DNA accessibility. Gene-specific disruption of transcription in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active Periphery.
Project description:Chloroplasts are organelles responsible for photosynthesis. They originated form a procaryotic ancestor in the process of endosymbiosis and contain their own genomes. The chloroplast genome is packaged into a chromatin-like structure known as the nucleoid. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging and connection of the nucleoid structure to gene expression remain poorly understood. We show that Arabidopsis thaliana chloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. Membrane association of specific DNA regions is correlated with high levels of transcription, high protein occupancy and reduced DNA accessibility. Genes with low levels of transcription are further away from the membranes, have lower protein occupancy and higher DNA accessibility. Gene-specific disruption of transcription in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active Periphery.
Project description:A pluripotent inducible cell line was generated from Arabidopsis to address the limitations of traditional in planta dicot systems and to develop a well-controlled experimental setup where the individual regulatory check points of chloroplast development could be defined. Following light exposure, this cell line was shown to differentiate into photosynthetically active cells with functional chloroplasts providing an experimental system with a temporal gradient of chloroplast development. Using this unique cell line from the dicot Arabidopsis we could demonstrate that the development from a proplastid to a functional chloroplast, and thereby the establishment of photosynthesis, is dependent on a regulatory mechanism involving two distinct phases. First, light exposure triggers an initial change in gene expression, metabolite profile, chlorophyll accumulation and plastid structure. Secondly, a second signal, most likely triggered by activation of the chloroplast, is required for full transition to a functional chloroplast and the shift from heterotrophic to photoautotrophic metabolism.
Project description:Chloroplasts are organelles responsible for photosynthesis. They originated form a procaryotic ancestor in the process of endosymbiosis and contain their own genomes. The chloroplast genome is packaged into a chromatin-like structure known as the nucleoid. The internal arrangement of the nucleoid, molecular mechanisms of DNA packaging and connection of the nucleoid structure to gene expression remain poorly understood. We show that Arabidopsis thaliana chloroplast nucleoids have a unique organization driven by DNA binding to the thylakoid membranes. Membrane association of specific DNA regions is correlated with high levels of transcription, high protein occupancy and reduced DNA accessibility. Genes with low levels of transcription are further away from the membranes, have lower protein occupancy and higher DNA accessibility. Gene-specific disruption of transcription in sigma factor mutants causes a corresponding reduction in membrane association, indicating that RNA polymerase activity causes DNA tethering to the membranes. We propose that transcription organizes the chloroplast nucleoid into a transcriptionally active membrane-associated core and a less active Periphery.
Project description:As the organelles in which photosynthesis occurs, chloroplasts are extremely susceptible to saline-alkali stress. Proteins from chloroplast were identified and quantified by isobaric tags for relative and absolute quantification (iTRAQ) strategy, and searched with both of Uniprot Liliposida database and NCBInr database. In each of the labeling experiments, approximately 700 proteins were identified, and 121 abundance changed proteins were identified in chloroplast under the condition of Na2CO3 treatment. While according to the subcellular localization prediction, 102 chloroplast localization abundance changed proteins were used for further analysis of the responsive mechanism of the chloroplast under the conditions of Na2CO3 treatment. The 102 proteins were classified into nine functional categories, including photosynthesis, energy metabolism, other metabolisms, stress and defense, membrane and transporting, signaling, chloroplast structure, gene expression, protein synthesis and folding, and miscellaneous. The abundance patterns of these proteins highlight the Na2CO3-responsive chloroplast structure modulation and a series of photosynthetic regulatory mechanisms, such as thermal dissipation, state transition, cyclic electron transport, photorespiration, repair of photodamaged PSII, alteration of PSI activity, and ROS homeostasis.
Project description:We present Structure-seq2, which provides nucleotide-resolution RNA structural information in vivo and genome-wide. This optimized version of our original Structure-seq method increases sensitivity and data quality by minimizing formation of a deleterious by-product, reducing ligation bias, and improving read coverage. Structure-seq2 can employ a biotinylated nucleotide to facilitate the protocol. We have benchmarked Structure-seq2 on both mRNA and rRNA structure in rice (Oryza sativa) and apply Structure-seq2 to provide evidence of hidden breaks in chloroplast rRNA and a previously unreported N1-methyladenosine (m1A) in a nuclear-encoded rRNA.
Project description:The regulator for chloroplast biogenesis (rcb) mutant was identified as a mutant defective in phytochrome-mediated chloroplast biogenesis. The rcb mutant has long hypocotyl and albino phenotypes. RCB initiates chloroplast biogenesis in the nucleus by promoting the degradation of the master repressors for chloroplast biogenesis, the PIFs (Phytochrome Interacting Factors). To understand how RCB regulates the expression of PIF-regulated genes, we performed genome-wide expression analysis of RCB-dependent genes using a rcb-10 null allele.
Project description:The coordination of chloroplast and nuclear genome status are critical for plant cell function, but the mechanism remain largely unclear. In this study, we report that Arabidopsis thaliana CHLOROPLAST AND NUCLEUS DUAL-LOCALIZED PROTEIN 1 (CND1) maintains genome stability in both the chloroplast and the nucleus.