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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 -
Trends in Plant Science Jun 2016Key steps in evolution are often singularities. The emergence of land plants is one such case and it is not immediately apparent why. A recent analysis found that the... (Review)
Review
Key steps in evolution are often singularities. The emergence of land plants is one such case and it is not immediately apparent why. A recent analysis found that the zygnematophycean algae represent the closest relative to embryophytes. Intriguingly, many exaptations thought essential to conquer land are common among various streptophytes, but zygnematophycean algae share with land plants the transfer of a few plastid genes to the nucleus. Considering the contribution of the chloroplast to terrestrialization highlights potentially novel exaptations that currently remain unexplored. We discuss how the streptophyte chloroplast evolved into what we refer to as the embryoplast, and argue this was as important for terrestrialization by freshwater algae as the host cell-associated exaptations that are usually focused upon.
Topics: Biodiversity; Biological Evolution; Fresh Water; Models, Biological; Plastids; Streptophyta
PubMed: 26895731
DOI: 10.1016/j.tplants.2016.01.021 -
Plant & Cell Physiology Jul 2016A plastid-localized terminal oxidase, PTox, was first described due to its role in chloroplast development, with plants lacking PTox producing white sectors on their... (Review)
Review
A plastid-localized terminal oxidase, PTox, was first described due to its role in chloroplast development, with plants lacking PTox producing white sectors on their leaves. This phenotype is explained as being due to PTox playing a role in carotenoid biosynthesis, as a cofactor of phytoene desaturase. Co-occurrence of PTox with a chloroplast-localized NADPH dehydrogenase (NDH) has suggested the possibility of a functional respiratory pathway in plastids. Evidence has also been found that, in certain stress-tolerant plant species, PTox can act as an electron acceptor from PSII, making it a candidate for engineering stress-tolerant crops. However, attempts to induce such a pathway via overexpression of the PTox protein have failed to date. Here we review the current understanding of PTox function in higher plants and discuss possible barriers to inducing PTox activity to improve stress tolerance.
Topics: Adaptation, Physiological; Electron Transport; Oxidoreductases; Plant Physiological Phenomena; Plastids; Stress, Physiological
PubMed: 26936791
DOI: 10.1093/pcp/pcw042 -
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 -
Plant Physiology and Biochemistry : PPB Aug 2010The plastid ndh genes encode components of the thylakoid Ndh complex which purportedly acts as an electron feeding valve to adjust the redox level of the cyclic... (Review)
Review
The plastid ndh genes encode components of the thylakoid Ndh complex which purportedly acts as an electron feeding valve to adjust the redox level of the cyclic photosynthetic electron transporters. During the process of evolution from endosymbiosis to modern chloroplast, most cyanobacterial genes were lost or transferred to nucleus. Eleven ndh genes are among the 150-200 genes remaining in higher plant chloroplast DNA, out of some 3000 genes in the original prokaryotic Cyanobacteria in which homologues to ndh genes encode components of the respiratory Complex I and probably other complexes. The ndh genes are absent in all sequenced plastid DNAs of algae except for the Charophyceae and some Prasinophyceae. With the possible exclusion of some Conifers and Gnetales, the plastid DNA of all photosynthetic land plants contains the ndh genes, whereas they are absent in epiphytic plants that have also lost genes for the photosynthetic machinery. Therefore, the functional role of the ndh genes seems closely related to the land adaptation of photosynthesis. Transcripts of several plastid genes require C to U editing. The ndh genes concentrate about 50% of the editing sites of angiosperm plastid transcripts. Editing sites may be remnants from an ancestor in which a number of T to C inactivating mutations took place in the ndh genes which, during evolution, are being corrected back to T. The comparison of homologous editing sites in the mRNAs of angiosperm ndh genes provides a tool to investigate selective and permissive environmental conditions of past evolutionary events.
Topics: Chloroplasts; Cyanobacteria; Eukaryota; Evolution, Molecular; NADPH Dehydrogenase; Plants; Plastids; RNA Editing
PubMed: 20493721
DOI: 10.1016/j.plaphy.2010.04.009 -
The Plant Cell Aug 2013Stromules are thin projections from plastids that are generally longer and more abundant on non-green plastids than on chloroplasts. Occasionally stromules can be... (Review)
Review
Stromules are thin projections from plastids that are generally longer and more abundant on non-green plastids than on chloroplasts. Occasionally stromules can be observed to connect two plastid bodies with one another. However, photobleaching of GFP-labeled plastids and stromules in 2000 demonstrated that plastids do not form a network like the endoplasmic reticulum, resulting in the proposal that stromules have major functions other than transfer of material from one plastid to another. The absence of a network was confirmed in 2012 with the use of a photoconvertible fluorescent protein, but the prior observations of movement of proteins between plastids were challenged. We review published evidence and provide new experiments that demonstrate trafficking of fluorescent protein between plastids as well as movement of proteins within stromules that emanate from a single plastid and discuss the possible function of stromules.
Topics: Arabidopsis; Green Fluorescent Proteins; Membrane Fusion; Photobleaching; Plastids; Protein Transport
PubMed: 23983219
DOI: 10.1105/tpc.113.112870 -
Annual Review of Plant Biology Apr 2017Plastoglobuli (PGs) are plastid lipoprotein particles surrounded by a membrane lipid monolayer. PGs contain small specialized proteomes and metabolomes. They are present... (Review)
Review
Plastoglobuli (PGs) are plastid lipoprotein particles surrounded by a membrane lipid monolayer. PGs contain small specialized proteomes and metabolomes. They are present in different plastid types (e.g., chloroplasts, chromoplasts, and elaioplasts) and are dynamic in size and shape in response to abiotic stress or developmental transitions. PGs in chromoplasts are highly enriched in carotenoid esters and enzymes involved in carotenoid metabolism. PGs in chloroplasts are associated with thylakoids and contain ∼30 core proteins (including six ABC1 kinases) as well as additional proteins recruited under specific conditions. Systems analysis has suggested that chloroplast PGs function in metabolism of prenyl lipids (e.g., tocopherols, plastoquinone, and phylloquinone); redox and photosynthetic regulation; plastid biogenesis; and senescence, including recycling of phytol, remobilization of thylakoid lipids, and metabolism of jasmonate. These functionalities contribute to chloroplast PGs' role in responses to stresses such as high light and nitrogen starvation. PGs are thus lipid microcompartments with multiple functions integrated into plastid metabolism, developmental transitions, and environmental adaptation. This review provides an in-depth overview of PG experimental observations, summarizes the present understanding of PG features and functions, and provides a conceptual framework for PG research and the realization of opportunities for crop improvement.
Topics: Adaptation, Physiological; Environment; Photosynthesis; Plant Proteins; Plants; Plastids; Terpenes
PubMed: 28125283
DOI: 10.1146/annurev-arplant-043015-111737 -
International Journal For Parasitology Apr 2000Both the chromosomal and extrachromosomal components of the apicomplexan genome have been supplemented by genes from a plastid-bearing endocytobiont: probably an algal... (Review)
Review
Both the chromosomal and extrachromosomal components of the apicomplexan genome have been supplemented by genes from a plastid-bearing endocytobiont: probably an algal cell. The sequence of the apicomplexan plastid's vestigial genome indicates that a large number (>100) of genes of endocytobiotic origin must have transferred laterally to the host cell nucleus where they control maintenance of the plastid organelle and supply its functional components by means of post-translational protein trafficking. Should the nuclear genes prove to be less divergent phylogenetically than those left on the plastid genome, they might give better clues than we have at present to the origin of the plastid-bearing endocytobiont. Most of these nuclear genes still await discovery, but the on-going genome sequencing project will reveal the function of the organelle, as well as many "housekeeping" processes of interest on a wider front. The plastid's own protein synthetic machinery, being cyanobacterial in origin, offers conventional targets for antibiotic intervention, and this is discussed here using a structural model of elongation factor Tu. Uncovering the vital function(s) of the plastid organelle will provide new drug targets.
Topics: Amino Acid Sequence; Animals; Apicomplexa; Models, Molecular; Molecular Sequence Data; Peptide Elongation Factor Tu; Phylogeny; Plastids; Porphobilinogen Synthase
PubMed: 10731566
DOI: 10.1016/s0020-7519(99)00185-x -
Current Opinion in Plant Biology Dec 2008Chloroplasts contain several thousand different proteins, of which more than 95% are encoded on nuclear genes, synthesized in the cytosol as precursor proteins, and... (Review)
Review
Chloroplasts contain several thousand different proteins, of which more than 95% are encoded on nuclear genes, synthesized in the cytosol as precursor proteins, and imported into the organelle. The major pathways for import and routing have been described; a general import apparatus in the chloroplast envelope and several ancestral translocases in the thylakoid membranes. In this update we focus on some interesting and emerging areas: the Tat translocase, which operates in parallel with the Sec system but transports folded proteins; different routes to the envelope membranes, which promises an understanding of the ways the Tic apparatus sorts transmembrane domains (TMDs) and may also uncover developmental relationships between envelope and thylakoids; and novel routes for proteins into chloroplasts including delivery from the secretory system.
Topics: Cell Compartmentation; Intracellular Membranes; Plant Proteins; Plastids; Protein Transport; Thylakoids
PubMed: 18990609
DOI: 10.1016/j.pbi.2008.10.008 -
Current Opinion in Plant Biology Dec 2008Plastid division is executed by the coordinated action of at least two molecular machineries--an internal machinery situated on the stromal side of the inner envelope... (Review)
Review
Plastid division is executed by the coordinated action of at least two molecular machineries--an internal machinery situated on the stromal side of the inner envelope membrane that was contributed by the cyanobacterial endosymbiont from which plastids evolved, and an external machinery situated on the cytosolic side of the outer envelope membrane that was contributed by the host. Here we review progress in defining the components of the plastid division complex and understanding the mechanisms of envelope constriction and division-site placement in plants. We also highlight recent work identifying the first molecular linkage between the internal and external division machineries, shedding light on how their mid-plastid positioning is coordinated across the envelope membranes. Little is known about the mechanisms that regulate plastid division in plant cells, but recent studies have begun to hint at potential mechanisms.
Topics: Cytosol; Plastids; Prokaryotic Cells; Time Factors
PubMed: 18990608
DOI: 10.1016/j.pbi.2008.10.001