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Molecular Cell Mar 2024Chloroplasts contain a dedicated genome that encodes subunits of the photosynthesis machinery. Transcription of photosynthesis genes is predominantly carried out by a...
Chloroplasts contain a dedicated genome that encodes subunits of the photosynthesis machinery. Transcription of photosynthesis genes is predominantly carried out by a plastid-encoded RNA polymerase (PEP), a nearly 1 MDa complex composed of core subunits with homology to eubacterial RNA polymerases (RNAPs) and at least 12 additional chloroplast-specific PEP-associated proteins (PAPs). However, the architecture of this complex and the functions of the PAPs remain unknown. Here, we report the cryo-EM structure of a 19-subunit PEP complex from Sinapis alba (white mustard). The structure reveals that the PEP core resembles prokaryotic and nuclear RNAPs but contains chloroplast-specific features that mediate interactions with the PAPs. The PAPs are unrelated to known transcription factors and arrange around the core in a unique fashion. Their structures suggest potential functions during transcription in the chemical environment of chloroplasts. These results reveal structural insights into chloroplast transcription and provide a framework for understanding photosynthesis gene expression.
Topics: RNA, Chloroplast; DNA-Directed RNA Polymerases; Chloroplasts; Plastids; Gene Expression Regulation, Plant; Transcription, Genetic
PubMed: 38428434
DOI: 10.1016/j.molcel.2024.02.003 -
Molecular Plant Jul 2014Chloroplasts (plastids) possess a genome and their own machinery to express it. Translation in plastids occurs on bacterial-type 70S ribosomes utilizing a set of tRNAs... (Review)
Review
Chloroplasts (plastids) possess a genome and their own machinery to express it. Translation in plastids occurs on bacterial-type 70S ribosomes utilizing a set of tRNAs that is entirely encoded in the plastid genome. In recent years, the components of the chloroplast translational apparatus have been intensely studied by proteomic approaches and by reverse genetics in the model systems tobacco (plastid-encoded components) and Arabidopsis (nucleus-encoded components). This work has provided important new insights into the structure, function, and biogenesis of chloroplast ribosomes, and also has shed fresh light on the molecular mechanisms of the translation process in plastids. In addition, mutants affected in plastid translation have yielded strong genetic evidence for chloroplast genes and gene products influencing plant development at various levels, presumably via retrograde signaling pathway(s). In this review, we describe recent progress with the functional analysis of components of the chloroplast translational machinery and discuss the currently available evidence that supports a significant impact of plastid translational activity on plant anatomy and morphology.
Topics: Genome, Plant; Plant Development; Plants; Plastids; Protein Biosynthesis
PubMed: 24589494
DOI: 10.1093/mp/ssu022 -
Biochimica Et Biophysica Acta Feb 2013The presence of genes encoding organellar proteins in both the nucleus and the organelle necessitates tight coordination of expression by the different genomes, and this... (Review)
Review
The presence of genes encoding organellar proteins in both the nucleus and the organelle necessitates tight coordination of expression by the different genomes, and this has led to the evolution of sophisticated intracellular signaling networks. Organelle-to-nucleus signaling, or retrograde control, coordinates the expression of nuclear genes encoding organellar proteins with the metabolic and developmental state of the organelle. Complex networks of retrograde signals orchestrate major changes in nuclear gene expression and coordinate cellular activities and assist the cell during plant development and stress responses. It has become clear that, even though the chloroplast depends on the nucleus for its function, plastid signals play important roles in an array of different cellular processes vital to the plant. Hence, the chloroplast exerts significant control over the running of the cell. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
Topics: Cell Communication; Cell Nucleus; Plant Cells; Plant Proteins; Plastids; Protein Transport; Signal Transduction
PubMed: 22749883
DOI: 10.1016/j.bbamcr.2012.06.020 -
Postepy Biochemii Sep 2020Plastoglobules (PGs), as important components of plastids, are involved in many stages of their development: from the chloroplast biogenesis through the... (Review)
Review
Plastoglobules (PGs), as important components of plastids, are involved in many stages of their development: from the chloroplast biogenesis through the chloroplast-chromoplast transformations, and finally in the process of gerontoplast formation. The unique protein and lipid composition of these structures, depending on their location, suggests that PGs are both a reservoir of spare materials and a center for many metabolic reactions. Plastoglobules play an active role in the metabolism of prenylquinones, carotenoids, and jasmonic acid, and are responsible for recycling of the thylakoid disintegration products. Their direct connection with the thylakoids allows for tight relationships between these two structures and redistribution of materials, which contributes to PGs’ role in response to stressful conditions. Moreover, strongly hydrophobic nature of plastoglobules, their specific proteome and a sufficiently simple isolation procedure create extraordinary possibilities of their application in plant biotechnology.
Topics: Chloroplasts; Plant Cells; Plastids; Proteome; Thylakoids
PubMed: 33315313
DOI: 10.18388/pb.2020_347 -
Philosophical Transactions of the Royal... Mar 2010Plastids and mitochondria each arose from a single endosymbiotic event and share many similarities in how they were reduced and integrated with their host. However, the... (Review)
Review
Plastids and mitochondria each arose from a single endosymbiotic event and share many similarities in how they were reduced and integrated with their host. However, the subsequent evolution of the two organelles could hardly be more different: mitochondria are a stable fixture of eukaryotic cells that are neither lost nor shuffled between lineages, whereas plastid evolution has been a complex mix of movement, loss and replacement. Molecular data from the past decade have substantially untangled this complex history, and we now know that plastids are derived from a single endosymbiotic event in the ancestor of glaucophytes, red algae and green algae (including plants). The plastids of both red algae and green algae were subsequently transferred to other lineages by secondary endosymbiosis. Green algal plastids were taken up by euglenids and chlorarachniophytes, as well as one small group of dinoflagellates. Red algae appear to have been taken up only once, giving rise to a diverse group called chromalveolates. Additional layers of complexity come from plastid loss, which has happened at least once and probably many times, and replacement. Plastid loss is difficult to prove, and cryptic, non-photosynthetic plastids are being found in many non-photosynthetic lineages. In other cases, photosynthetic lineages are now understood to have evolved from ancestors with a plastid of different origin, so an ancestral plastid has been replaced with a new one. Such replacement has taken place in several dinoflagellates (by tertiary endosymbiosis with other chromalveolates or serial secondary endosymbiosis with a green alga), and apparently also in two rhizarian lineages: chlorarachniophytes and Paulinella (which appear to have evolved from chromalveolate ancestors). The many twists and turns of plastid evolution each represent major evolutionary transitions, and each offers a glimpse into how genomes evolve and how cells integrate through gene transfers and protein trafficking.
Topics: Biological Evolution; Chlorophyta; Dinoflagellida; Eukaryota; Gene Transfer, Horizontal; Mitochondria; Models, Biological; Phylogeny; Plastids; Rhodophyta; Symbiosis
PubMed: 20124341
DOI: 10.1098/rstb.2009.0103 -
Current Biology : CB Jan 2009A comprehensive understanding of the origin and spread of plastids remains an important yet elusive goal in the field of eukaryotic evolution. Combined with the... (Review)
Review
A comprehensive understanding of the origin and spread of plastids remains an important yet elusive goal in the field of eukaryotic evolution. Combined with the discovery of new photosynthetic and non-photosynthetic protist lineages, the results of recent taxonomically broad phylogenomic studies suggest that a re-shuffling of higher-level eukaryote systematics is in order. Consequently, new models of plastid evolution involving ancient secondary and tertiary endosymbioses are needed to explain the full spectrum of photosynthetic eukaryotes.
Topics: Animals; Biological Evolution; Cyanobacteria; Eukaryotic Cells; Gene Transfer, Horizontal; Photosynthesis; Phylogeny; Plastids; Symbiosis
PubMed: 19174147
DOI: 10.1016/j.cub.2008.11.067 -
Protoplasma Oct 2012Plastid genetic engineering has come of age, becoming today an attractive alternative approach for the expression of foreign genes, as it offers several advantages over... (Review)
Review
Plastid genetic engineering has come of age, becoming today an attractive alternative approach for the expression of foreign genes, as it offers several advantages over nuclear transformants. Significant progress has been made in plastid genetic engineering in tobacco and other Solanaceae plants, through the use of improved regeneration procedures and transformation vectors with efficient promoters and untranslated regions. Many genes encoding for industrially important proteins and vaccines, as well as genes conferring important agronomic traits, have been stably integrated and expressed in the plastid genome. Despite these advances, it remains a challenge to achieve marked levels of plastid transgene expression in non-green tissues. In this review, we summarize the basic requirements of plastid genetic engineering and discuss the current status, limitations, and the potential of plastid transformation for expanding future studies relating to Solanaceae plants.
Topics: Genetic Engineering; Genetic Vectors; Plastids; Solanaceae
PubMed: 22395455
DOI: 10.1007/s00709-012-0391-9 -
Microbiology (Reading, England) Sep 2022is a unicellular photosynthetic eukaryotic flagellate of the Discoba supergroup, which also encompasses Kinetoplastida and Diplonema. Plastids have green algal origin...
is a unicellular photosynthetic eukaryotic flagellate of the Discoba supergroup, which also encompasses Kinetoplastida and Diplonema. Plastids have green algal origin and are secondarily acquired. The nuclear genome is extremely large and many genes suggest multiple endosymbiotic/gene transfer events, i.e. derivation from prokaryotes of various lineages. is remarkably robust and can proliferate in environments contaminated with heavy metals and acids. Extraordinary metabolic plasticity and a mixotrophic lifestyle confers an ability to thrive in a broad range of environments, as well as facilitating production of many novel metabolites, making of considerable biotechnological importance.
Topics: Chlorophyta; Euglena gracilis; Photosynthesis; Plastids; Symbiosis
PubMed: 36178464
DOI: 10.1099/mic.0.001241 -
Essays in Biochemistry Apr 2018Plastids are critical organelles in plant cells that perform diverse functions and are central to many metabolic pathways. Beyond their major roles in primary... (Review)
Review
Plastids are critical organelles in plant cells that perform diverse functions and are central to many metabolic pathways. Beyond their major roles in primary metabolism, of which their role in photosynthesis is perhaps best known, plastids contribute to the biosynthesis of phytohormones and other secondary metabolites, store critical biomolecules, and sense a range of environmental stresses. Accordingly, plastid-derived signals coordinate a host of physiological and developmental processes, often by emitting signalling molecules that regulate the expression of nuclear genes. Several excellent recent reviews have provided broad perspectives on plastid signalling pathways. In this review, we will highlight recent advances in our understanding of chloroplast signalling pathways. Our discussion focuses on new discoveries illuminating how chloroplasts determine life and death decisions in cells and on studies elucidating tetrapyrrole biosynthesis signal transduction networks. We will also examine the role of a plastid RNA helicase, ISE2, in chloroplast signalling, and scrutinize intriguing results investigating the potential role of stromules in conducting signals from the chloroplast to other cellular locations.
Topics: Chloroplasts; Genome, Plant; Oxidative Stress; Plants; Plastids; RNA Helicases; Signal Transduction; Tetrapyrroles
PubMed: 29563221
DOI: 10.1042/EBC20170011 -
Current Biology : CB Jun 2015The number and nature of endosymbioses involving red algal endosymbionts are debated. Gene phylogenies have become the most popular tool to untangle this issue, but they... (Review)
Review
The number and nature of endosymbioses involving red algal endosymbionts are debated. Gene phylogenies have become the most popular tool to untangle this issue, but they deliver conflicting results. As gene and lineage sampling has increased, so have both the number of conflicting trees and the number of suggestions in the literature for multiple tertiary, and even quaternary, symbioses that might reconcile the tree conflicts. Independent lines of evidence that can address the issue are needed. Here we summarize the mechanism and machinery of protein import into complex red plastids. The process involves protein translocation machinery, known as SELMA, that arose once in evolution, that facilitates protein import across the second outermost of the four plastid membranes, and that is always targeted specifically to that membrane, regardless of where it is encoded today. It is widely accepted that the unity of protein import across the two membranes of primary plastids is strong evidence for their single cyanobacterial origin. Similarly, the unity of SELMA-dependent protein import across the second outermost plastid membrane constitutes strong evidence for the existence of a single red secondary endosymbiotic event at the common origin of all red complex plastids. We furthermore propose that the two outer membranes of red complex plastids are derived from host endoplasmic reticulum in the initial red secondary endosymbiotic event.
Topics: Models, Biological; Phylogeny; Plastids; Protein Transport; Symbiosis
PubMed: 26079086
DOI: 10.1016/j.cub.2015.04.033