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Traffic (Copenhagen, Denmark) May 2007Chloroplasts are descendants of cyanobacteria and divide by binary fission. Several components of the division apparatus have been identified in the past several years... (Review)
Review
Chloroplasts are descendants of cyanobacteria and divide by binary fission. Several components of the division apparatus have been identified in the past several years and we are beginning to appreciate the plastid division process at a mechanistic level. In this review, we attempt to summarize the most recent developments in the field and assemble these observations into a working model of plastid division in plants.
Topics: Arabidopsis Proteins; Chloroplasts; Dynamins; Models, Biological; Plant Proteins; Plastids
PubMed: 17451550
DOI: 10.1111/j.1600-0854.2007.00545.x -
Molecular Biology and Evolution Apr 2022Ochrophyta is an algal group belonging to the Stramenopiles and comprises diverse lineages of algae which contribute significantly to the oceanic ecosystems as primary...
Ochrophyta is an algal group belonging to the Stramenopiles and comprises diverse lineages of algae which contribute significantly to the oceanic ecosystems as primary producers. However, early evolution of the plastid organelle in Ochrophyta is not fully understood. In this study, we provide a well-supported tree of the Stramenopiles inferred by the large-scale phylogenomic analysis that unveils the eukaryvorous (nonphotosynthetic) protist Actinophrys sol (Actinophryidae) is closely related to Ochrophyta. We used genomic and transcriptomic data generated from A. sol to detect molecular traits of its plastid and we found no evidence of plastid genome and plastid-mediated biosynthesis, consistent with previous ultrastructural studies that did not identify any plastids in Actinophryidae. Moreover, our phylogenetic analyses of particular biosynthetic pathways provide no evidence of a current and past plastid in A. sol. However, we found more than a dozen organellar aminoacyl-tRNA synthases (aaRSs) that are of algal origin. Close relationships between aaRS from A. sol and their ochrophyte homologs document gene transfer of algal genes that happened before the divergence of Actinophryidae and Ochrophyta lineages. We further showed experimentally that organellar aaRSs of A. sol are targeted exclusively to mitochondria, although organellar aaRSs in Ochrophyta are dually targeted to mitochondria and plastids. Together, our findings suggested that the last common ancestor of Actinophryidae and Ochrophyta had not yet completed the establishment of host-plastid partnership as seen in the current Ochrophyta species, but acquired at least certain nuclear-encoded genes for the plastid functions.
Topics: Ecosystem; Evolution, Molecular; Genome, Plastid; Phylogeny; Plants; Plastids; Stramenopiles
PubMed: 35348760
DOI: 10.1093/molbev/msac065 -
Current Biology : CB Sep 2023Plastid symbioses between heterotrophic hosts and algae are widespread and abundant in surface oceans. They are critically important both for extant ecological systems...
Plastid symbioses between heterotrophic hosts and algae are widespread and abundant in surface oceans. They are critically important both for extant ecological systems and for understanding the evolution of plastids. Kleptoplastidy, where the plastids of prey are temporarily retained and continuously re-acquired, provides opportunities to study the transitional states of plastid establishment. Here, we investigated the poorly studied marine centrohelid Meringosphaera and its previously unidentified symbionts using culture-independent methods from environmental samples. Investigations of the 18S rDNA from single-cell assembled genomes (SAGs) revealed uncharacterized genetic diversity within Meringosphaera that likely represents multiple species. We found that Meringosphaera harbors plastids of Dictyochophyceae origin (stramenopiles), for which we recovered six full plastid genomes and found evidence of two distinct subgroups that are congruent with host identity. Environmental monitoring by qPCR and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) revealed seasonal dynamics of both host and plastid. In particular, we did not detect the plastids for 6 months of the year, which, combined with the lack of plastids in some SAGs, suggests that the plastids are temporary and the relationship is kleptoplastidic. Importantly, we found evidence of genetic integration of the kleptoplasts as we identified host-encoded plastid-associated genes, with evolutionary origins likely from the plastid source as well as from other alga sources. This is only the second case where host-encoded kleptoplast-targeted genes have been predicted in an ancestrally plastid-lacking group. Our results provide evidence for gene transfers and protein re-targeting as relatively early events in the evolution of plastid symbioses.
Topics: Symbiosis; In Situ Hybridization, Fluorescence; Genome; Plastids; Phylogeny
PubMed: 37536342
DOI: 10.1016/j.cub.2023.07.017 -
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 -
Philosophical Transactions of the Royal... Jan 2003The topic of the transition of the genome of a free-living bacterial organism to that of an organelle is addressed by considering three cases. Two of these are... (Review)
Review
The topic of the transition of the genome of a free-living bacterial organism to that of an organelle is addressed by considering three cases. Two of these are relatively clear-cut as involving respectively organisms (cyanobacteria) and organelles (plastids). Cyanobacteria are usually free-living but some are involved in symbioses with a range of eukaryotes in which the cyanobacterial partner contributes photosynthesis, nitrogen fixation, or both of these. In several of these symbioses the cyanobacterium is vertically transmitted, and in a few instances, sufficient unsuccessful attempts have been made to culture the cyanobiont independently for the association to be considered obligate for the cyanobacterium. Plastids clearly had a cyanobacterial ancestor but cannot grow independently of the host eukaryote. Plastid genomes have at most 15% of the number of genes encoded by the cyanobacterium with the smallest number of genes; more genes than are retained in the plastid genome have been transferred to the eukaryote nuclear genome, while the rest of the cyanobacterial genes have been lost. Even the most cyanobacteria-like plastids, for example the "cyanelles" of glaucocystophyte algae, are functionally and genetically very similar to other plastids and give little help in indicating intermediates in the evolution of plastids. The third case considered is the vertically transmitted intracellular bacterial symbionts of insects where the symbiosis is usually obligate for both partners. The number of genes encoded by the genomes of these obligate symbionts is intermediate between that of organelles and that of free-living bacteria, and the genomes of the insect symbionts also show rapid rates of sequence evolution and AT (adenine, thymine) bias. Genetically and functionally, these insect symbionts show considerable similarity to organelles.
Topics: Animals; Cyanobacteria; Eukaryotic Cells; Evolution, Molecular; Genes, Bacterial; Genome; Insecta; Plastids; Symbiosis
PubMed: 12594915
DOI: 10.1098/rstb.2002.1188 -
Traffic (Copenhagen, Denmark) May 2008The accurate targeting of proteins to their final destination is an essential process in all living cells. Apicomplexans are obligate intracellular protozoan parasites... (Review)
Review
The accurate targeting of proteins to their final destination is an essential process in all living cells. Apicomplexans are obligate intracellular protozoan parasites that possess a compartmental organization similar to that of free-living eukaryotes but can be viewed as professional secretory cells. Establishment of parasitism involves the sequential secretion from highly specialized secretory organelles, including micronemes, rhoptries and dense granules. Additionally, apicomplexans harbor a tubular mitochondrion, a nonphotosynthetic plastid organelle termed the apicoplast, acidocalcisomes and an elaborated inner membrane complex composed of flattened membrane cisternae that are derived from the secretory pathway. Given the multitude of destinations both inside and outside the parasite, the endoplasmic reticulum/Golgi of the apicomplexans constitutes one of the most busy roads intersections in eukaryotic traffic.
Topics: Animals; Endoplasmic Reticulum; Golgi Apparatus; Humans; Plasmodium falciparum; Plastids; Protein Transport; Protozoan Proteins; Toxoplasma
PubMed: 18331382
DOI: 10.1111/j.1600-0854.2008.00713.x -
Plant Physiology Apr 2011
Review
Topics: Biological Evolution; Cercozoa; Genome, Plastid; Plant Cells; Plastids; Protein Sorting Signals; Protein Transport; Symbiosis
PubMed: 21343425
DOI: 10.1104/pp.111.173500 -
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 -
BMC Evolutionary Biology Jun 2010Plastid replacements through secondary endosymbioses include massive transfer of genes from the endosymbiont to the host nucleus and require a new targeting system to...
BACKGROUND
Plastid replacements through secondary endosymbioses include massive transfer of genes from the endosymbiont to the host nucleus and require a new targeting system to enable transport of the plastid-targeted proteins across 3-4 plastid membranes. The dinoflagellates are the only eukaryotic lineage that has been shown to have undergone several plastid replacement events, and this group is thus highly relevant for studying the processes involved in plastid evolution. In this study, we analyzed the phylogenetic origin and N-terminal extensions of plastid-targeted proteins from Lepidodinium chlorophorum, a member of the only dinoflagellate genus that harbors a green secondary plastid rather than the red algal-derived, peridinin-containing plastid usually found in photosynthetic dinoflagellates.
RESULTS
We sequenced 4,746 randomly picked clones from a L. chlorophorum cDNA library. 22 of the assembled genes were identified as genes encoding proteins functioning in plastids. Some of these were of green algal origin. This confirms that genes have been transferred from the plastid to the host nucleus of L. chlorophorum and indicates that the plastid is fully integrated as an organelle in the host. Other nuclear-encoded plastid-targeted protein genes, however, are clearly not of green algal origin, but have been derived from a number of different algal groups, including dinoflagellates, streptophytes, heterokonts, and red algae. The characteristics of N-terminal plastid-targeting peptides of all of these genes are substantially different from those found in peridinin-containing dinoflagellates and green algae.
CONCLUSIONS
L. chlorophorum expresses plastid-targeted proteins with a range of different origins, which probably arose through endosymbiotic gene transfer (EGT) and horizontal gene transfer (HGT). The N-terminal extension of the genes is different from the extensions found in green alga and other dinoflagellates (peridinin- and haptophyte plastids). These modifications have likely enabled the mosaic proteome of L. chlorophorum.
Topics: Amino Acid Sequence; Dinoflagellida; Evolution, Molecular; Gene Library; Gene Transfer, Horizontal; Molecular Sequence Data; Phylogeny; Plastids; Proteome; RNA, Protozoan; Sequence Alignment; Sequence Analysis, DNA; Symbiosis
PubMed: 20565933
DOI: 10.1186/1471-2148-10-191 -
Biochimica Et Biophysica Acta 2015Plastid endosymbiosis defines a process through which a fully evolved cyanobacterial ancestor has transmitted to a eukaryotic phagotroph the hundreds of genes required... (Review)
Review
Plastid endosymbiosis defines a process through which a fully evolved cyanobacterial ancestor has transmitted to a eukaryotic phagotroph the hundreds of genes required to perform oxygenic photosynthesis, together with the membrane structures, and cellular compartment associated with this process. In this review, we will summarize the evidence pointing to an active role of Chlamydiales in metabolic integration of free living cyanobacteria, within the cytosol of the last common plant ancestor.
Topics: Biological Evolution; Chlamydiales; Host-Pathogen Interactions; Plants; Plastids; Symbiosis
PubMed: 25687892
DOI: 10.1016/j.bbabio.2015.02.007