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Plastid

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Plastid
Plant cells with visiblechloroplasts
Scientific classificationEdit this classification
Domain: Bacteria
Phylum: Cyanobacteria
Clade: Plastid

Aplastidis amembrane-bound organellefound in thecellsofplants,algae,and some othereukaryoticorganisms. Plastids are considered to be intracellularendosymbioticcyanobacteria.[1]

Examples of plastids includechloroplasts(used forphotosynthesis);chromoplasts(used for synthesis and storage of pigments);leucoplasts(non-pigmented plastids some of which candifferentiate); andapicoplasts(non-photosynthetic plastids ofapicomplexaderived from secondary endosymbiosis).

A permanent primary endosymbiosis event occurred about 1.5 billion years ago in theArchaeplastidaclade—land plants,red algae,green algae—probably with acyanobiont,a symbiotic cyanobacteria related to the genusGloeomargarita.[2][3]Another primary endosymbiosis event occurred later, between 140 to 90 million years ago, in the photosynthetic plastidsPaulinellaamoeboidsof the cyanobacteria generaProchlorococcusandSynechococcus,or the "PS-clade".[4][5]Secondary and tertiary endosymbiosisevents have also occurred in a wide variety of organisms; and some organisms developed the capacity to sequester ingested plastids—a process known askleptoplasty.

A. F. W. Schimper[6][a]was the first to name, describe, and provide a clear definition of plastids, which possess adouble-stranded DNAmolecule that long has been thought of as circular in shape, like that of thecircular chromosomeofprokaryotic cells—but now, perhaps not; (see"..a linear shape"). Plastids are sites for manufacturing and storing pigments and other important chemical compounds used by the cells ofautotrophiceukaryotes.Some containbiological pigmentssuch as used inphotosynthesisor which determine a cell's color. Plastids in organisms that have lost their photosynthetic properties are highly useful for manufacturing molecules like theisoprenoids.[8]

In land plants

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Plastid types
Leucoplastsin plant cells.

Chloroplasts, proplastids, and differentiation

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Inland plants,the plastids that containchlorophyllcan performphotosynthesis,thereby creating internal chemical energy from externalsunlight energywhile capturing carbon from Earth's atmosphere and furnishing the atmosphere with life-giving oxygen. These are thechlorophyll-plastids—and they are namedchloroplasts;(see top graphic).

Other plastids can synthesizefatty acidsandterpenes,which may be used to produce energy or as raw material to synthesize other molecules. For example, plastidepidermal cellsmanufacture the components of the tissue system known asplant cuticle,including itsepicuticular wax,frompalmitic acid—which itself is synthesized in the chloroplasts of themesophyll tissue.Plastids function to store different components includingstarches,fats,andproteins.[9]

All plastids are derived from proplastids, which are present in themeristematicregions of the plant. Proplastids and young chloroplasts typically divide bybinary fission,but more mature chloroplasts also have this capacity.

Plantproplastids(undifferentiated plastids) maydifferentiateinto several forms, depending upon which function they perform in the cell, (see top graphic). They may develop into any of the following variants:[10]

Leucoplasts differentiate into even more specialized plastids, such as:

Depending on their morphology and target function, plastids have the ability to differentiate or redifferentiate between these and other forms.

Plastomes and Chloroplast DNA/ RNA; plastid DNA and plastid nucleoids

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Each plastid creates multiple copies of its own unique genome, orplastome,(from 'plastid genome')—which for a chlorophyll plastid (or chloroplast) is equivalent to a 'chloroplast genome', or a 'chloroplast DNA'.[11][12]The number of genome copies produced per plastid is variable, ranging from 1000 or more inrapidly dividing new cells,encompassing only a few plastids, down to 100 or less in mature cells, encompassing numerous plastids.

A plastome typically contains agenomethat encodestransferribonucleic acids(tRNA)s andribosomalribonucleic acids(rRNAs). It also contains proteins involved in photosynthesis and plastid genetranscriptionandtranslation.But these proteins represent only a small fraction of the total protein set-up necessary to build and maintain any particular type of plastid.Nucleargenes (in the cell nucleus of a plant) encode the vast majority of plastid proteins; and the expression of nuclear and plastid genes is co-regulated to coordinate the development anddifferentionof plastids.

Many plastids, particularly those responsible for photosynthesis, possess numerous internal membrane layers. Plastid DNA exists as protein-DNA complexes associated as localizedregionswithin the plastid's inner envelopemembrane;and these complexes are called 'plastidnucleoids'. Unlike the nucleus of a eukaryotic cell, a plastid nucleoid isnotsurrounded by a nuclear membrane. The region of each nucleoid may contain more than 10 copies of the plastid DNA.

Where the proplastid (undifferentiated plastid) contains a single nucleoid region located near the centre of the proplastid, thedeveloping (or differentiating) plastidhas many nucleoids localized at the periphery of the plastid and bound to the inner envelope membrane. During the development/ differentiation of proplastids to chloroplasts—and when plastids are differentiating from one type to another—nucleoids change in morphology, size, and location within the organelle. The remodelling of plastid nucleoids is believed to occur by modifications to the abundance of and the composition of nucleoid proteins.

In normalplant cellslong thin protuberances calledstromulessometimes form—extending from the plastid body into the cellcytosolwhile interconnecting several plastids. Proteins and smaller molecules can move around and through the stromules. Comparatively, in the laboratory, most cultured cells—which are large compared to normal plant cells—produce very long and abundant stromules that extend to the cell periphery.

In 2014, evidence was found of the possible loss of plastid genome inRafflesialagascae,a non-photosyntheticparasiticflowering plant, and inPolytomella,a genus of non-photosyntheticgreen algae.Extensive searches for plastid genes in bothtaxonsyielded no results, but concluding that their plastomes are entirely missing is still disputed.[13]Some scientists argue that plastid genome loss is unlikely since even these non-photosynthetic plastids contain genes necessary to complete variousbiosynthetic pathwaysincluding heme biosynthesis.[13][14]

Even with any loss of plastid genome inRafflesiaceae,the plastids still occur there as "shells" without DNA content,[15]which is reminiscent ofhydrogenosomesin various organisms.

In algae and protists

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Plastid types inalgaeandprotistsinclude:

The plastid of photosyntheticPaulinellaspecies is often referred to as the 'cyanelle' or chromatophore, and is used in photosynthesis.[17][18]It had a much more recent endosymbiotic event, in the range of 140–90 million years ago, which is the only other known primary endosymbiosis event of cyanobacteria.[19][20]

Etioplasts,amyloplastsandchromoplastsare plant-specific and do not occur in algae.[citation needed]Plastids in algae andhornwortsmay also differ from plant plastids in that they containpyrenoids.

Inheritance

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In reproducing, most plants inherit their plastids from only one parent. In general,angiospermsinherit plastids from the femalegamete,where manygymnospermsinherit plastids from the malepollen.Algae also inherit plastids from just one parent. Thus the plastid DNA of the other parent is completely lost.

In normal intraspecific crossings—resulting in normal hybrids of one species—the inheriting of plastid DNA appears to be strictly uniparental; i.e., from the female. In interspecific hybridisations, however, the inheriting is apparently more erratic. Although plastids are inherited mainly from the female in interspecific hybridisations, there are many reports of hybrids of flowering plants producing plastids from the male. Approximately 20% of angiosperms, includingalfalfa(Medicago sativa), normally show biparental inheriting of plastids.[21]

DNA damage and repair

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The plastidDNAofmaizeseedlings is subjected to increasing damage as the seedlings develop.[22]The DNA damage is due to oxidative environments created byphoto-oxidative reactionsandphotosynthetic/respiratory electron transfer.Some DNA molecules arerepairedbut DNA with unrepaired damage is apparently degraded to non-functional fragments.

DNA repairproteins are encoded by the cell'snuclear genomeand then translocated to plastids where they maintaingenomestability/ integrity by repairing the plastid's DNA.[23]For example, inchloroplastsof the mossPhyscomitrella patens,a protein employed in DNA mismatch repair (Msh1) interacts with proteins employed in recombinational repair (RecAand RecG) to maintain plastid genome stability.[24]

Origin

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Plastids are thought to be descended fromendosymbioticcyanobacteria.The primary endosymbiotic event of the Archaeplastida is hypothesized to have occurred around 1.5 billion years ago[25]and enabled eukaryotes to carry outoxygenic photosynthesis.[26]Three evolutionary lineages in the Archaeplastida have since emerged in which the plastids are named differently: chloroplasts ingreen algaeand/or plants,rhodoplastsinred algae,andmuroplastsin the glaucophytes. The plastids differ both in their pigmentation and in their ultrastructure. For example, chloroplasts in plants and green algae have lost allphycobilisomes,thelight harvesting complexesfound in cyanobacteria, red algae and glaucophytes, but instead containstromaand granathylakoids.The glaucocystophycean plastid—in contrast to chloroplasts and rhodoplasts—is still surrounded by the remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes.

The plastid of photosyntheticPaulinellaspecies is often referred to as the 'cyanelle' or chromatophore, and had a much more recent endosymbiotic event about 90–140 million years ago; it is the only known primary endosymbiosis event of cyanobacteria outside of the Archaeplastida.[17][18]The plastid belongs to the "PS-clade" (of the cyanobacteria generaProchlorococcusandSynechococcus), which is a different sister clade to the plastids belonging to the Archaeplastida.[4][5]

In contrast to primary plastids derived from primary endosymbiosis of a prokaryoctyic cyanobacteria, complex plastids originated by secondaryendosymbiosisin which a eukaryotic organism engulfed another eukaryotic organism that contained a primary plastid.[27]When aeukaryoteengulfs a red or a green alga and retains the algal plastid, that plastid is typically surrounded by more than two membranes. In some cases these plastids may be reduced in their metabolic and/or photosynthetic capacity. Algae with complex plastids derived by secondary endosymbiosis of a red alga include theheterokonts,haptophytes,cryptomonads,and mostdinoflagellates(= rhodoplasts). Those that endosymbiosed a green alga include theeuglenidsandchlorarachniophytes(= chloroplasts). TheApicomplexa,a phylum ofobligate parasiticalveolatesincluding the causative agents ofmalaria(Plasmodiumspp.),toxoplasmosis(Toxoplasma gondii), and many other human or animal diseases also harbor a complex plastid (although this organelle has been lost in some apicomplexans, such asCryptosporidium parvum,which causescryptosporidiosis). The 'apicoplast' is no longer capable of photosynthesis, but is an essential organelle, and a promisingtargetforantiparasitic drugdevelopment.

Somedinoflagellatesandsea slugs,in particular of the genusElysia,take up algae as food and keep the plastid of the digested alga to profit from the photosynthesis; after a while, the plastids are also digested. This process is known askleptoplasty,from the Greek,kleptes(κλέπτης), thief.

Plastid development cycle

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An illustration of the stages of inter-conversion in plastids

In 1977 J.M Whatley proposed a plastid development cycle which said that plastid development is not always unidirectional but is instead a complicated cyclic process. Proplastids are the precursor of the more differentiated forms of plastids, as shown in the diagram to the right.[28]

See also

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  • Mitochondrion– Organelle in eukaryotic cells responsible for respiration
  • Cytoskeleton– Network of filamentous proteins that forms the internal framework of cells
  • Photosymbiosis– Type of symbiotic relationship

Notes

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  1. ^SometimesErnst Haeckelis credited to coin the term plastid, but his "plastid" includes nucleated cells and anucleated "cytodes"[7]and thus totally different concept from the plastid in modern literature.

References

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  1. ^Sato N (2007). "Origin and Evolution of Plastids: Genomic View on the Unification and Diversity of Plastids". In Wise RR, Hoober JK (eds.).The Structure and Function of Plastids.Advances in Photosynthesis and Respiration. Vol. 23. Springer Netherlands. pp. 75–102.doi:10.1007/978-1-4020-4061-0_4.ISBN978-1-4020-4060-3.
  2. ^Moore KR, Magnabosco C, Momper L, Gold DA, Bosak T, Fournier GP (2019)."An Expanded Ribosomal Phylogeny of Cyanobacteria Supports a Deep Placement of Plastids".Frontiers in Microbiology.10:1612.doi:10.3389/fmicb.2019.01612.PMC6640209.PMID31354692.
  3. ^Vries, Jan de; Gould, Sven B. (2018-01-15)."The monoplastidic bottleneck in algae and plant evolution".Journal of Cell Science.131(2): jcs203414.doi:10.1242/jcs.203414.ISSN0021-9533.PMID28893840.
  4. ^abMarin, Birger; Nowack, Eva CM; Glöckner, Gernot; Melkonian, Michael (2007-06-05)."The ancestor of the Paulinella chromatophore obtained a carboxysomal operon by horizontal gene transfer from a Nitrococcus-like γ-proteobacterium".BMC Evolutionary Biology.7(1): 85.Bibcode:2007BMCEE...7...85M.doi:10.1186/1471-2148-7-85.PMC1904183.PMID17550603.
  5. ^abOchoa de Alda, Jesús A. G.; Esteban, Rocío; Diago, María Luz; Houmard, Jean (2014-01-29)."The plastid ancestor originated among one of the major cyanobacterial lineages".Nature Communications.5(1): 4937.Bibcode:2014NatCo...5.4937O.doi:10.1038/ncomms5937.ISSN2041-1723.PMID25222494.
  6. ^Schimper, A.F.W. (1882) "Ueber die Gestalten der Stärkebildner und Farbkörper"Botanisches Centralblatt12(5): 175–178.
  7. ^Haeckel, E. (1866) "Morphologische Individuen erster Ordnung: Plastiden oder Plasmastücke"in hisGenerelle Morphologie der OrganismenBd. 1, pp. 269-289
  8. ^Picozoans Are Algae After All: Study | The Scientist Magazine®
  9. ^Kolattukudy, P.E. (1996) "Biosynthetic pathways of cutin and waxes, and their sensitivity to environmental stresses", pp. 83–108 in:Plant Cuticles.G. Kerstiens (ed.), BIOS Scientific publishers Ltd., Oxford
  10. ^abWise, Robert R. (2006). "The Diversity of Plastid Form and Function".The Structure and Function of Plastids.Advances in Photosynthesis and Respiration. Vol. 23. Springer. pp. 3–26.doi:10.1007/978-1-4020-4061-0_1.ISBN978-1-4020-4060-3.
  11. ^Wicke, S; Schneeweiss, GM; dePamphilis, CW; Müller, KF; Quandt, D (2011)."The evolution of the plastid chromosome in land plants: gene content, gene order, gene function".Plant Molecular Biology.76(3–5): 273–297.doi:10.1007/s11103-011-9762-4.PMC3104136.PMID21424877.
  12. ^Wicke, S; Naumann, J (2018)."Molecular evolution of plastid genomes in parasitic flowering plants".Advances in Botanical Research.85:315–347.doi:10.1016/bs.abr.2017.11.014.ISBN9780128134573.
  13. ^ab"Plants Without Plastid Genomes".The Scientist.Retrieved2015-09-26.
  14. ^Barbrook AC, Howe CJ, Purton S (February 2006). "Why are plastid genomes retained in non-photosynthetic organisms?".Trends in Plant Science.11(2): 101–8.doi:10.1016/j.tplants.2005.12.004.PMID16406301.
  15. ^"DNA of Giant 'Corpse Flower' Parasite Surprises Biologists".April 2021.
  16. ^Viola R, Nyvall P, Pedersén M (July 2001)."The unique features of starch metabolism in red algae".Proceedings. Biological Sciences.268(1474): 1417–22.doi:10.1098/rspb.2001.1644.PMC1088757.PMID11429143.
  17. ^abLhee, Duckhyun; Ha, Ji-San; Kim, Sunju; Park, Myung Gil; Bhattacharya, Debashish; Yoon, Hwan Su (2019-02-22)."Evolutionary dynamics of the chromatophore genome in three photosynthetic Paulinella species - Scientific Reports".Scientific Reports.9(1): 2560.Bibcode:2019NatSR...9.2560L.doi:10.1038/s41598-019-38621-8.PMC6384880.PMID30796245.
  18. ^abGabr, Arwa; Grossman, Arthur R.; Bhattacharya, Debashish (2020-05-05). Palenik, B. (ed.)."Paulinella, a model for understanding plastid primary endosymbiosis".Journal of Phycology.56(4). Wiley: 837–843.Bibcode:2020JPcgy..56..837G.doi:10.1111/jpy.13003.ISSN0022-3646.PMC7734844.PMID32289879.
  19. ^Sánchez-Baracaldo, Patricia; Raven, John A.; Pisani, Davide; Knoll, Andrew H. (2017-09-12)."Early photosynthetic eukaryotes inhabited low-salinity habitats".Proceedings of the National Academy of Sciences.114(37): E7737–E7745.Bibcode:2017PNAS..114E7737S.doi:10.1073/pnas.1620089114.ISSN0027-8424.PMC5603991.PMID28808007.
  20. ^Luis Delaye; Cecilio Valadez-Cano; Bernardo Pérez-Zamorano (15 March 2016)."How Really Ancient Is Paulinella Chromatophora?".PLOS Currents.8.doi:10.1371/CURRENTS.TOL.E68A099364BB1A1E129A17B4E06B0C6B.ISSN2157-3999.PMC4866557.PMID28515968.WikidataQ36374426.
  21. ^Zhang Q (March 2010). "Why does biparental plastid inheritance revive in angiosperms?".Journal of Plant Research.123(2): 201–6.Bibcode:2010JPlR..123..201Z.doi:10.1007/s10265-009-0291-z.PMID20052516.S2CID5108244.
  22. ^Kumar RA, Oldenburg DJ, Bendich AJ (December 2014)."Changes in DNA damage, molecular integrity, and copy number for plastid DNA and mitochondrial DNA during maize development".Journal of Experimental Botany.65(22): 6425–39.doi:10.1093/jxb/eru359.PMC4246179.PMID25261192.
  23. ^Oldenburg DJ, Bendich AJ (2015)."DNA maintenance in plastids and mitochondria of plants".Frontiers in Plant Science.6:883.doi:10.3389/fpls.2015.00883.PMC4624840.PMID26579143.
  24. ^Odahara M, Kishita Y, Sekine Y (August 2017)."MSH1 maintains organelle genome stability and genetically interacts with RECA and RECG in the moss Physcomitrella patens".The Plant Journal.91(3): 455–465.doi:10.1111/tpj.13573.PMID28407383.
  25. ^Ochoa de Alda JA, Esteban R, Diago ML, Houmard J (September 2014)."The plastid ancestor originated among one of the major cyanobacterial lineages".Nature Communications.5:4937.Bibcode:2014NatCo...5.4937O.doi:10.1038/ncomms5937.PMID25222494.
  26. ^Hedges SB, Blair JE, Venturi ML, Shoe JL (January 2004)."A molecular timescale of eukaryote evolution and the rise of complex multicellular life".BMC Evolutionary Biology.4:2.doi:10.1186/1471-2148-4-2.PMC341452.PMID15005799.
  27. ^Chan CX, Bhattachary D (2010)."The Origin of Plastids".Nature Education.3(9): 84.
  28. ^Whatley, Jean M. (1978)."A Suggested Cycle of Plastid Developmental Interrelationships".The New Phytologist.80(3): 489–502.doi:10.1111/j.1469-8137.1978.tb01581.x.ISSN0028-646X.JSTOR2431207.

Further reading

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