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International Journal of Molecular... Mar 2021Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage... (Review)
Review
Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage lipids from reactive oxygen species (ROS). ROS are byproducts of aerobic metabolism that can damage cell components, they are also known to play a role in signaling. Plants are particularly prone to oxidative damage because oxygenic photosynthesis results in O formation in their green tissues. In addition, the photosynthetic electron transfer chain is an important source of ROS. Therefore, chloroplasts are the main site of ROS generation in plant cells during the light reactions of photosynthesis, and plastidic antioxidants are crucial to prevent oxidative stress, which occurs when plants are exposed to various types of stress factors, both biotic and abiotic. The increase in antioxidant content during stress acclimation is a common phenomenon. In the present review, we describe the mechanisms of ROS (singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radical) production in chloroplasts in general and during exposure to abiotic stress factors, such as high light, low temperature, drought and salinity. We highlight the dual role of their presence: negative (i.e., lipid peroxidation, pigment and protein oxidation) and positive (i.e., contribution in redox-based physiological processes). Then we provide a summary of current knowledge concerning plastidic prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, as well as their structure, occurrence, biosynthesis and function both in ROS detoxification and signaling.
Topics: Antioxidants; Chloroplasts; Chromans; Plastids; Quinones; Reactive Oxygen Species; Terpenes
PubMed: 33799456
DOI: 10.3390/ijms22062950 -
Cells May 2021Photosynthesis has to work efficiently in contrasting environments such as in shade and full sun. Rapid changes in light intensity and over-reduction of the... (Review)
Review
Photosynthesis has to work efficiently in contrasting environments such as in shade and full sun. Rapid changes in light intensity and over-reduction of the photosynthetic electron transport chain cause production of reactive oxygen species, which can potentially damage the photosynthetic apparatus. Thus, to avoid such damage, photosynthetic electron transport is regulated on many levels, including light absorption in antenna, electron transfer reactions in the reaction centers, and consumption of ATP and NADPH in different metabolic pathways. Many regulatory mechanisms involve the movement of protein-pigment complexes within the thylakoid membrane. Furthermore, a certain number of chloroplast proteins exist in different oligomerization states, which temporally associate to the thylakoid membrane and modulate their activity. This review starts by giving a short overview of the lipid composition of the chloroplast membranes, followed by describing supercomplex formation in cyclic electron flow. Protein movements involved in the various mechanisms of non-photochemical quenching, including thermal dissipation, state transitions and the photosystem II damage-repair cycle are detailed. We highlight the importance of changes in the oligomerization state of VIPP and of the plastid terminal oxidase PTOX and discuss the factors that may be responsible for these changes. Photosynthesis-related protein movements and organization states of certain proteins all play a role in acclimation of the photosynthetic organism to the environment.
Topics: Chloroplasts; Electron Transport; Oxidation-Reduction; Photosynthesis; Plants; Thylakoids
PubMed: 34065690
DOI: 10.3390/cells10051216 -
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 -
Plant Communications Mar 2021Plant cells contain three organelles that harbor DNA: the nucleus, plastids, and mitochondria. Plastid transformation has emerged as an attractive platform for the... (Review)
Review
Plant cells contain three organelles that harbor DNA: the nucleus, plastids, and mitochondria. Plastid transformation has emerged as an attractive platform for the generation of transgenic plants, also referred to as transplastomic plants. Plastid genomes have been genetically engineered to improve crop yield, nutritional quality, and resistance to abiotic and biotic stresses, as well as for recombinant protein production. Despite many promising proof-of-concept applications, transplastomic plants have not been commercialized to date. Sequence-specific nuclease technologies are widely used to precisely modify nuclear genomes, but these tools have not been applied to edit organelle genomes because the efficient homologous recombination system in plastids facilitates plastid genome editing. Unlike plastid transformation, successful genetic transformation of higher plant mitochondrial genome transformation was tested in several research group, but not successful to date. However, stepwise progress has been made in modifying mitochondrial genes and their transcripts, thus enabling the study of their functions. Here, we provide an overview of advances in organelle transformation and genome editing for crop improvement, and we discuss the bottlenecks and future development of these technologies.
Topics: Cell Nucleus; Crops, Agricultural; Gene Editing; Genome, Plant; Mitochondria; Plant Breeding; Plastids
PubMed: 33898977
DOI: 10.1016/j.xplc.2021.100141 -
Current Biology : CB Jun 2021Rapidly accumulating genetic data from environmental sequencing approaches have revealed an extraordinary level of unsuspected diversity within marine phytoplankton,...
Rapidly accumulating genetic data from environmental sequencing approaches have revealed an extraordinary level of unsuspected diversity within marine phytoplankton, which is responsible for around 50% of global net primary production. However, the phenotypic identity of many of the organisms distinguished by environmental DNA sequences remains unclear. The rappemonads represent a plastid-bearing protistan lineage that to date has only been identified by environmental plastid 16S rRNA sequences. The phenotypic identity of this group, which does not confidently cluster in any known algal clades in 16S rRNA phylogenetic reconstructions, has remained unknown since the first report of environmental sequences over two decades ago. We show that rappemonads are closely related to a haptophyte microalga, Pavlomulina ranunculiformis gen. nov. et sp. nov., and belong to a new haptophyte class, the Rappephyceae. Organellar phylogenomic analyses provide strong evidence for the inclusion of this lineage within the Haptophyta as a sister group to the Prymnesiophyceae. Members of this new class have a cosmopolitan distribution in coastal and oceanic regions. The relative read abundance of Rappephyceae in a large environmental barcoding dataset was comparable to, or greater than, those of major haptophyte species, such as the bloom-forming Gephyrocapsa huxleyi and Prymnesium parvum, and this result indicates that they likely have a significant impact as primary producers. Detailed characterization of Pavlomulina allowed for reconstruction of the ancient evolutionary history of the Haptophyta, a group that is one of the most important components of extant marine phytoplankton communities.
Topics: Haptophyta; Phylogeny; Phytoplankton; Plastids; RNA, Ribosomal, 16S
PubMed: 33773100
DOI: 10.1016/j.cub.2021.03.012 -
Journal of Phycology Aug 2020The uptake and conversion of a free-living cyanobacterium into a photosynthetic organelle by the single-celled Archaeplastida ancestor helped transform the biosphere... (Review)
Review
The uptake and conversion of a free-living cyanobacterium into a photosynthetic organelle by the single-celled Archaeplastida ancestor helped transform the biosphere from low to high oxygen. There are two documented, independent cases of plastid primary endosymbiosis. The first is the well-studied instance in Archaeplastida that occurred ca. 1.6 billion years ago, whereas the second occurred 90-140 million years ago, establishing a permanent photosynthetic compartment (the chromatophore) in amoebae in the genus Paulinella. Here, we briefly summarize knowledge about plastid origin in the Archaeplastida and then focus on Paulinella. In particular, we describe features of the Paulinella chromatophore that make it a model for examining earlier events in the evolution of photosynthetic organelles. Our review stresses recently gained insights into the evolution of chromatophore and nuclear encoded DNA sequences in Paulinella, metabolic connectivity between the endosymbiont and cytoplasm, and systems that target proteins into the chromatophore. We also describe future work with Paulinella, and the potential rewards and challenges associated with developing further this model system.
Topics: Amoeba; Biological Evolution; Chromatophores; Phylogeny; Plastids; Rhizaria; Symbiosis
PubMed: 32289879
DOI: 10.1111/jpy.13003 -
International Journal of Molecular... Jan 2021Light is an important cue that stimulates both plastid development and biosynthesis of carotenoids in plants. During photomorphogenesis or de-etiolation, photoreceptors... (Review)
Review
Light is an important cue that stimulates both plastid development and biosynthesis of carotenoids in plants. During photomorphogenesis or de-etiolation, photoreceptors are activated and molecular factors for carotenoid and chlorophyll biosynthesis are induced thereof. In fruits, light is absorbed by in the early stages of ripening, which allows a gradual synthesis of carotenoids in the peel and pulp with the onset of chromoplasts' development. In roots, only a fraction of light reaches this tissue, which is not required for carotenoid synthesis, but it is essential for root development. When exposed to light, roots start greening due to chloroplast development. However, the colored taproot of carrot grown underground presents a high carotenoid accumulation together with chromoplast development, similar to citrus fruits during ripening. Interestingly, total carotenoid levels decrease in carrots roots when illuminated and develop chloroplasts, similar to normal roots exposed to light. The recent findings of the effect of light quality upon the induction of molecular factors involved in carotenoid synthesis in leaves, fruit, and roots are discussed, aiming to propose consensus mechanisms in order to contribute to the understanding of carotenoid synthesis regulation by light in plants.
Topics: Biosynthetic Pathways; Carotenoids; Chloroplasts; Fruit; Light; Photosynthesis; Plant Development; Plant Leaves; Plant Physiological Phenomena; Plant Roots; Plastids
PubMed: 33530294
DOI: 10.3390/ijms22031184 -
Current Opinion in Microbiology Oct 2021The apicoplast is the relict of a plastid organelle found in several disease-causing apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii. In these... (Review)
Review
The apicoplast is the relict of a plastid organelle found in several disease-causing apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii. In these organisms, the organelle has lost its photosynthetic capability but harbours several fitness-conferring or essential metabolic pathways. Although maintaining the apicoplast and fuelling the metabolic pathways within requires the challenging constant import and export of numerous metabolites across its four membranes, only few apicoplast transporters have been identified to date, most of which are orphan transporters. Here we review the roles of metabolic pathways within the apicoplast and what is currently known about the few identified apicoplast metabolite transporters. We discuss what metabolites must get in and out of the apicoplast, the many transporters that are yet to be discovered, and what role these might play in parasite metabolism and as putative drug targets.
Topics: Animals; Apicomplexa; Apicoplasts; Metabolic Networks and Pathways; Parasites; Plasmodium; Toxoplasma
PubMed: 34455306
DOI: 10.1016/j.mib.2021.07.016 -
International Journal of Molecular... Dec 2022In a circular economy era the transition towards renewable and sustainable materials is very urgent. The development of bio-based solutions, that can ensure... (Review)
Review
In a circular economy era the transition towards renewable and sustainable materials is very urgent. The development of bio-based solutions, that can ensure technological circularity in many priority areas (e.g., agriculture, biotechnology, ecology, green industry, etc.), is very strategic. The agricultural and fishing industry wastes represent important feedstocks that require the development of sustainable and environmentally-friendly industrial processes to produce and recover biofuels, chemicals and bioactive molecules. In this context, the replacement, in industrial processes, of chemicals with enzyme-based catalysts assures great benefits to humans and the environment. In this review, we describe the potentiality of the plastid transformation technology as a sustainable and cheap platform for the production of recombinant industrial enzymes, summarize the current knowledge on the technology, and display examples of cellulolytic enzymes already produced. Further, we illustrate several types of bacterial auxiliary and chitinases/chitin deacetylases enzymes with high biotechnological value that could be manufactured by plastid transformation.
Topics: Humans; Biotechnology; Biofuels; Plastids; Industrial Waste; Agriculture
PubMed: 36499577
DOI: 10.3390/ijms232315254 -
Gene duplication and rate variation in the evolution of plastid ACCase and Clp genes in angiosperms.Molecular Phylogenetics and Evolution Mar 2022While the chloroplast (plastid) is known for its role in photosynthesis, it is also involved in many other metabolic pathways essential for plant survival. As such,...
While the chloroplast (plastid) is known for its role in photosynthesis, it is also involved in many other metabolic pathways essential for plant survival. As such, plastids contain an extensive suite of enzymes required for non-photosynthetic processes. The evolution of the associated genes has been especially dynamic in flowering plants (angiosperms), including examples of gene duplication and extensive rate variation. We examined the role of ongoing gene duplication in two key plastid enzymes, the acetyl-CoA carboxylase (ACCase) and the caseinolytic protease (Clp), responsible for fatty acid biosynthesis and protein turnover, respectively. In plants, there are two ACCase complexes-a homomeric version present in the cytosol and a heteromeric version present in the plastid. Duplications of the nuclear-encoded homomeric ACCase gene and retargeting of one resultant protein to the plastid have been previously reported in multiple species. We find that these retargeted homomeric ACCase proteins exhibit elevated rates of sequence evolution, consistent with neofunctionalization and/or relaxation of selection. The plastid Clp complex catalytic core is composed of nine paralogous proteins that arose via ancient gene duplication in the cyanobacterial/plastid lineage. We show that further gene duplication occurred more recently in the nuclear-encoded core subunits of this complex, yielding additional paralogs in many species of angiosperms. Moreover, in six of eight cases, subunits that have undergone recent duplication display increased rates of sequence evolution relative to those that have remained single copy. We also compared substitution patterns between pairs of Clp core paralogs to gain insight into post-duplication evolutionary routes. These results show that gene duplication and rate variation continue to shape the plastid proteome.
Topics: Acetyl-CoA Carboxylase; Gene Duplication; Magnoliopsida; Peptide Hydrolases; Phylogeny; Plastids
PubMed: 35033670
DOI: 10.1016/j.ympev.2022.107395