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Encyclopedia > Plastid
Plant cells with visible chloroplasts.
Plant cells with visible chloroplasts.

Plastids are major organelles found in plants and algae. Image File history File linksMetadata No higher resolution available. ... Schematic of typical animal cell, showing subcellular components. ...

Contents

Plastids in plants

Plastids are responsible for photosynthesis, storage of products like starch and for the synthesis of many classes of molecules such as fatty acids and terpenes which are needed as cellular building blocks and/or for the function of the plant. Depending on their morphology and function, plastids have the ability to differentiate, or redifferentiate, between these and other forms. All plastids are derived from proplastids (formerly "eoplasts", eo-: dawn, early), which are present in the meristematic regions of the plant. Proplastids and young chloroplasts commonly divide, but more mature chloroplasts also have this capacity. In plants, plastids may differentiate into several forms, depending upon which function they need to play in the cell. Undifferentiated plastids (proplastids) may develop into any of the following plastids: In chemistry, especially biochemistry, a fatty acid is a carboxylic acid (or organic acid), often with a long aliphatic tail (long chains), either saturated or unsaturated. ... Terpenes are a class of hydrocarbons, produced by many plants, particularly conifers. ... Embryonic stem cells differentiate into cells in various body organs. ... Plastids are major organelles uouououuoououououofound only in plants and algae. ... For other uses, see Plant (disambiguation). ... Embryonic stem cells differentiate into cells in various body organs. ...

Each plastid creates multiple copies of the rectangular 75-250 kilo bases plastid genome. The number of genome copies per plastid is flexible, ranging from more than 1000 in rapidly dividing cells, which generally contain few plastids, to 100 or fewer in mature cells, where plastid divisions has given rise to a large number of plastids. The plastid genome contains about 100 genes encoding ribosomal and transfer ribonucleic acids (rRNAs and tRNAs) as well as proteins involved in photosynthesis and plastid gene transcription and translation. However, these proteins only represent a small fraction of the total protein set-up necessary to build and maintain the structure and function of a particular type of plastid. Nuclear genes encode the vast majority of plastid proteins, and the expression of plastid genes and nuclear genes is tightly co-regulated to allow proper development of plastids in relation to cell differentiation. Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... The leaf is the primary site of photosynthesis in plants. ... An etioplast is a chloroplast that has not been exposed to light. ... Chromoplasts are plastids responsible for pigment synthesis and storage. ... In molecular biology, the unwanted substances that are taken in by a cell are turned into leukoplasts which create more energy for the chloroplasts and are the building blocks of chloroplasts. ... Many terpenes are derived from conifer resins, here a pine. ... Amyloplasts in a potato cell Amyloplasts (are a form of leucoplasts) are non-pigmented organelles found in plant cells responsible for the storage of starch through the polymerisation of glucose. ... Starch (CAS# 9005-25-8) is a complex carbohydrate which is insoluble in water; it is used by plants as a way to store excess glucose. ... Statoliths are a specialised form of amyloplasts involved in gravity perception by plants. ... Gravity is a force of attraction that acts between bodies that have mass. ... Elaioplasts are plastids found in plant cells responsible for the storage of fat. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... Proteinoplasts (sometimes called proteoplasts and aleuronaplasts) are specialized organelles found only in plant cells. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Base pairs, of a DNA molecule. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... This does not adequately cite its references or sources. ... For other uses, see Gene (disambiguation). ... Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The leaf is the primary site of photosynthesis in plants. ... A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... Look up translate in Wiktionary, the free dictionary. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ...


Plastid DNA exists as large protein-DNA complexes associated with the inner envelope membrane and called 'plastid nucleoids'. Each nucleoid particle may contain more than 10 copies of the plastid DNA. The proplastid contains a single nucleoid located in the centre of the plastid. The developing plastid has many nucleoids, localized at the periphery of the plastid, bound to the inner envelope membrane. During the development of proplastids to chloroplasts, and when plastids convert from one type to another, nucleoids change in morphology, size and location within the organelle. The remodelling of nucleoids is believed to occur by modifications to the composition and abundance of nucleoid proteins. The inner membrane is a membrane (phospholipid bilayer) of an organelle that is within the outer membrane. ...


In plant cells long thin protuberances called stromules sometimes form and extend from the main plastid body into the cytosol and interconnect several plastids. Proteins, and presumably smaller molecules, can move within stromules. Most cultured cells that are relatively large compared to other plant cells have very long and abundant stromules that extend to the cell periphery. Plant cell structure Plant cells are quite different from the cells of the other eukaryotic kingdoms organisms. ... Stromules are microscopic structures found in plant cells. ... The cytosol (cf. ... Stromules are microscopic structures found in plant cells. ...


Plastids in algae

In algae, the term leucoplast (leukoplast) is used for all unpigmented plastids. Their function differ from the leukoplasts in plants. Etioplast, amyloplast and chromoplast are plant-specific and do not occur in algae. Algal plastids may also differ from plant plastids in that they contain pyrenoids. A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... An etioplast is a chloroplast that has not been exposed to light. ... Amyloplasts in a potato cell Amyloplasts (are a form of leucoplasts) are non-pigmented organelles found in plant cells responsible for the storage of starch through the polymerisation of glucose. ... Chromoplasts are plastids responsible for pigment synthesis and storage. ... In cell biology, pyrenoids are centers of carbon dioxide fixation. ...


Inheritance of plastids

Most plants inherit the plastids from only one parent. Angiosperms generally inherit plastids from the mother, while many gymnosperms inherit plastids from the father. Algae also inherit plastids from only one parent. The plastid DNA of the other parent is thus completely lost. Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants (also angiosperms or Magnoliophyta) are one of the major groups of modern plants, comprising those that produce seeds in specialized reproductive organs called flowers, where the ovulary or carpel is enclosed. ... Gymnosperms are seed-bearing, vascular plants. ... A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ...


In normal intraspecific crossings (resulting in normal hybrids of one species), the inheritance of plastid DNA appears to be quite strictly 100% uniparental. In interspecific hybridisations, however, the inheritance of plastids appears to be more erratic. Although plastids inherit mainly maternally in interspecific hybridisations, there are many reports of hybrids of flowering plants that contain plastids of the father.


Origin of plastids

Plastids are thought to have originated from endosymbiotic cyanobacteria. They developed around 1500 mya and allowed eukaryotes to carry out oxygenic photosynthesis.[1] Due to a split-up into three evolutionary lineages, the plastids are named differently: chloroplasts in green algae and plants, rhodoplasts in red algae and cyanelles in the glaucophytes. The plastids differ by their pigmentation, but also in ultrastructure. The chloroplasts e.g. have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but - only in plants and in closely related green algae - contain stroma and grana thylakoids. The glaucocystophycean plastid - in contrast to the chloroplasts and the rhodoplasts - is still surrounded by a remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes. An endosymbiont (also known as intracellular symbiont) is any organism that lives within cells of another organism, i. ... Orders The taxonomy of the Cyanobacteria is currently under revision. ... Divisions Chlorophyta Charophyta Green algae are microscopic protists; found in all aquatic environments, including marine, freshwater and brackish water. ... For other uses, see Plant (disambiguation). ... Possible classes Florideophyceae Bangiophyceae Cyanidiophyceae Red algae (Rhodophyta, pronounced /ˈrəʊdə(ʊ)ˌfʌɪtə/) are a large group of mostly multicellular, marine algae, including many notable seaweeds. ... The glaucophytes, also referred to as glaucocystophytes or glaucocystids, are a tiny group of freshwater algae. ... It has been suggested that this article or section be merged with Photosynthesis. ... Thylakoids (commonly referred to as Thylakoid membranes) are a phospholipid bilayer membrane-bound compartment internal to chloroplasts, and represent the majority of its internal structure. ...


Complex plastids start by secondary endosymbiosis, when a eukaryote engulfs a red or green alga and retains the algal plastid, which is typically surrounded by more than two membranes, and reduced in its metabolic and/or photosynthetic capacity. Algae with complex plastids derived by secondary endosymbiosis of a red alga include the heterokonts, haptophytes, cryptomonads, and most dinoflagellates (= rhodoplasts). Those that endosymbiosed a green alga include the euglenids and chlorarachniophytes (= chloroplasts). The Apicomplexa, a phylum of obligate parasitic protozoa including the causative agents of malaria (Plasmodium spp.), 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 as Cryptosporidium parvum, which causes cryptosporidiosis). The 'apicoplast' is no longer capable of photosynthesis, but is an essential organelle, and a promising target for antiparasitic drug development. An endosymbiont (also known as intracellular symbiont) is any organism that lives within cells of another organism, i. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Typical classes Colored groups Chrysophyceae (golden algae) Synurophyceae Actinochrysophyceae (axodines) Pelagophyceae Phaeothamniophyceae Bacillariophyceae (diatoms) Bolidophyceae Raphidophyceae Eustigmatophyceae Xanthophyceae (yellow-green algae) Phaeophyceae (brown algae) Colorless groups Oomycetes (water moulds) Hypochytridiomycetes Bicosoecea Labyrinthulomycetes (slime nets) Opalinea Proteromonadea The heterokonts or stramenopiles are a major line of eukaryotes containing about 10,500... Orders Class Pavlovophyceae    Pavlovales Class Prymnesiophyceae    Prymnesiales    Phaeocystales    Isochrysidales    Coccolithales The haptophytes, classed either as the Prymnesiophyta or Haptophyta, are a group of algae. ... Typical genera Campylomonas Chilomonas Chroomonas Cryptomonas Falcomonas Geminigera Goniomonas Guillardia Hemiselmis Plagioselmis Proteomonas Storeatula Rhodomonas Teleaulax The cryptomonads are a small group of flagellates, most of which have chloroplasts. ... Classes Dinophyceae Noctiluciphyceae Syndiniophyceae The dinoflagella are a large group of flagellate protists. ... Major groups Phototrophs    Euglenales    Eutreptiales Osmotrophs    Rhabdomonadales Phagotrophs    ?Heteronematales    ?Sphenomonadales The euglenids (also spelled euglenoids) are one of the best-known groups of flagellates, commonly found in freshwater especially when it is rich in organic materials, with a few marine and endosymbiotic members. ... Genera Chlorarachnion Gymnochlora Lotharella Cryptochlora Chlorarachniophytes are a small group of algae occasionally found in tropical oceans. ... Classes & Subclasses Aconoidasida Haemosporasina Piroplasmasina Blastocystea Conoidasida Coccidiasina Gregarinasina The Apicomplexa are a large group of protozoa, characterized by the presence of a unique organelle called an apical complex. ... Species Plasmodium achiotense Plasmodium achromaticum Plasmodium acuminatum Plasmodium adunyinkai Plasmodium aegyptensis Plasmodium aeuminatum Plasmodium agamae Plasmodium anasum Plasmodium anomaluri Plasmodium arachniformis Plasmodium ashfordi Plasmodium atheruri Plasmodium aurulentum Plasmodium australis Plasmodium attenuatum Plasmodium azurophilum Plasmodium balli Plasmodium bambusicolai Plasmodium basilisci Plasmodium beebei Plasmodium beltrani Plasmodium berghei Plasmodium bertii Plasmodium bigueti Plasmodium... It has been suggested that Tachyzoite, Tachyzoites and Bradyzoite be merged into this article or section. ... Binomial name Cryptosporidium parvum Cryptosporidium parvum is one of several species that cause cryptosporidiosis. ... Cryptosporidiosis is a parasitic disease affecting the intestines of mammals that is caused by Cryptosporidium, a protozoan parasite in the phylum Apicomplexa. ... The Apicoplast is a relict, non-photosynthetic plastid found in the malaria parasite, Plasmodium falciparum. ...


Some dinoflagellates 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. These captured plastids are known as kleptoplastids. Classes Dinophyceae Noctiluciphyceae Syndiniophyceae The dinoflagellates are a large group of flagellate protists. ...


Sources

  • A Novel View of Chloroplast Structure: contains fluorescence images of chloroplasts and stromules as well as an easy to read chapter.
  • Continuous expression in tobacco leaves of a Brassica napus PEND homologue blocks differentiation of plastids and development of palisade cells Wycliffe et al., 2005. The Plant Journal Volume 44 Issue 1 Page 1. PMID: 16167891
  • Birky, C. W. 2001. The inheritance of genes in mitochondria and chloroplasts: laws, mechanisms and models. Annual Review of Genetics 35: 125-148.

Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Stromules are microscopic structures found in plant cells. ...

=References

  1. ^ Hedges, S. Blair et al. (2004) "A molecular timescale of eukaryote evolution and the rise of complex multicellular life" BMC Evolutionary Biology 4:2

Further reading=

Bhattacharya, D. (Ed.) 1997 Origins of Algae and their Plastids. Springer-Verlag/Wein, New York. ISBN 3-211-83036-7


  Results from FactBites:
 
Plastid (227 words)
Plastids are the organelles in plants and algae in which photosynthesis occurs.
Plastids are divided into several types depending on morphology and function: chloroplasts, leucoplasts, amyloplasts, and chromoplasts.
Plastids are divided into three evolutionary lineages: green plastids are chloroplasts, red plastids are rhodoplasts, and blue-green plastids are the cyanelles.
plastid: Definition and Much More from Answers.com (1188 words)
Plastids are responsible for photosynthesis, storage of products like starch and for the synthesis of many classes of molecules such as fatty acids and terpenes which are needed as cellular building blocks and/or for the function of the plant.
Nuclear genes encode the vast majority of plastid proteins, and the expression of plastid genes and nuclear genes is tightly co-regulated to allow proper development of plastids in relation to cell differentiation.
The glaucocystophycean plastid - in contrast to the chloroplasts and the rhodoplasts - is still surrounded by a remains of the cyanobacterial cell wall.
  More results at FactBites »

 
 

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