Prasinophyte

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Prasinophyte
Paraphyletic group of chlorophytes
Pyramimonas sp color.jpg
Pyramimonas sp.
Scientific classification OOjs UI icon edit-ltr.svg
Clade: Viridiplantae
Division: Chlorophyta
Informal group: Prasinophyte
Included classes [1] [2]
Excluded classes
(i.e. chlorophytes not considered prasinophytes)

The prasinophytes are a group of unicellular green algae. [3] Prasinophytes mainly include marine planktonic species, as well as some freshwater representatives. [3] [4] The prasinophytes are morphologically diverse, including flagellates with one to eight flagella and non-motile (coccoid) unicells. The cells of many species are covered with organic body scales; others are naked. [4] Well studied genera include Ostreococcus , considered to be the smallest (ca. 0.95 μm) free-living eukaryote, [5] and Micromonas , both of which are found in marine waters worldwide. Prasinophytes have simple cellular structures, containing a single chloroplast and a single mitochondrion. The genomes are relatively small compared to other eukaryotes (about 12 Mbp for Ostreococcus [6] [7] and 21 Mbp for Micromonas [8] ). At least one species, the Antarctic form Pyramimonas gelidicola , is capable of phagocytosis and is therefore a mixotrophic algae. [9]

Contents

Some authors treat the prasinophytes as a polyphyletic grouping of green algae from different clades. As the Tetraphytina emerged in the Prasinophytes, recently authors include it, rendering it monophyletic, and equivalent to chlorophyta. [10] [11]

Morphology

Representation of a Prasinophyte Flagellum Flagellar hairs Flagellar scales Pit, for communication or fluid exchange Contractile vacuole, regulates the quantity of water inside a cell Vacuole Basal body Rhizoplast, a striated, fibrous root Golgi apparatus, modifies proteins and sends them out of the cell Endoplasmic reticulum, the transport network for molecules going to specific parts of the cell Endosome, sorts material Nucleolus Nucleus Eyespot, photoreceptor used to sense light direction and intensity Plastid membranes (2, primary) Pyrenoid, center of carbon fixation Starch granule Cytoplasmic channel Thylakoids, site of the light-dependent reactions of photosynthesis Glycoprotein theca Mitochondrion, creates ATP (energy) for the cell (flat cristae) 2023 Prasinophyte.svg
Representation of a Prasinophyte
  1. Flagellum
  2. Flagellar hairs
  3. Flagellar scales
  4. Pit, for communication or fluid exchange
  5. Contractile vacuole, regulates the quantity of water inside a cell
  6. Vacuole
  7. Basal body
  8. Rhizoplast, a striated, fibrous root
  9. Golgi apparatus, modifies proteins and sends them out of the cell
  10. Endoplasmic reticulum, the transport network for molecules going to specific parts of the cell
  11. Endosome, sorts material
  12. Nucleolus
  13. Nucleus
  14. Eyespot, photoreceptor used to sense light direction and intensity
  15. Plastid membranes (2, primary)
  16. Pyrenoid, center of carbon fixation
  17. Starch granule
  18. Cytoplasmic channel
  19. Thylakoids, site of the light-dependent reactions of photosynthesis
  20. Glycoprotein theca
  21. Mitochondrion, creates ATP (energy) for the cell (flat cristae)

Ecology

A study of photosynthetic gene-sequence diversity (rbcL) in the Gulf of Mexico indicated that Prasinophytes are particularly prevalent at the Subsurface Chlorophyll Maximum (SCM) [12] and several different ecotypes of Ostreococcus have been detected in the environment. [13] These ecotypes were thought to be distinguished in the environment by their adaptation to light intensities. O. lucimarinus was isolated from a high-light environment [14] and observed year-round in the coastal North Pacific Ocean. [15] RCC141 was considered low-light, because it was isolated from the lower euphotic zone. These strains, or ecotypes, were later shown to live in different habitats (open-ocean or mesotrophic) and their distributions do not appear to be connected to light availability. [16] O. tauri was isolated from a coastal lagoon and appears to be light-polyvalent. Genetic data indicates that distinct molecular differences exist between the different ecotypes that have been detected. [17]

Prasinophytes are subject to infection by large double-stranded DNA viruses belonging to the genus Prasinovirus in the family Phycodnaviridae , [18] [19] [20] as well as a Reovirus. [21] It has been estimated that from 2 to 10% of the Micromonas pusilla population is lysed per day by viruses. [22]

Phylogeny

Recent studies agree that the prasinophytes are not a natural group, being highly paraphyletic. [4] [23] [24] [25] Relationships among the groups making up the Chlorophyta are not fully resolved. The cladogram produced by Leliaert et al. 2011 [4] and some modification according to Silar 2016, [26] Leliaert 2016 [27] and Lopes dos Santos et al. 2017 [1] is shown below. The blue shaded groups are or have traditionally been placed in the Prasinophyceae [3] ). The species Mesostigma viride has been shown to be a member of the Streptophyta or basal Green algae. The others are member of the Chlorophyta.

Green Algae

As 2020 paper places the Palmophyllophyceae (prasinophyte clade VI) in a new phylum outside of the Chlorophyta and Streptophyta, the Prasinodermophyta. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Chlorophyta</span> Phylum of green algae

Chlorophyta is a division of green algae informally called chlorophytes.

<span class="mw-page-title-main">Green algae</span> Paraphyletic group of eukaryotes

The green algae are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as a sister of the Zygnematophyceae. Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds. There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments, or highly differentiated macroscopic seaweeds.

<span class="mw-page-title-main">Streptophyta</span> Clade consisting of the charophyte algae and land plants

Streptophyta, informally the streptophytes, is a clade of plants. The composition of the clade varies considerably between authors, but the definition employed here includes land plants and all green algae except the Chlorophyta and the more basal Prasinodermophyta.

<span class="mw-page-title-main">Charophyta</span> Phylum of algae

Charophyta is a group of freshwater green algae, called charophytes, sometimes treated as a division, yet also as a superdivision or an unranked clade. The terrestrial plants, the Embryophyta emerged deep within Charophyta, possibly from terrestrial unicellular charophytes, with the class Zygnematophyceae as a sister group.

<span class="mw-page-title-main">Viridiplantae</span> Clade of archaeplastids including green algae and the land plants

Viridiplantae constitute a clade of eukaryotic organisms that comprises approximately 450,000–500,000 species that play important roles in both terrestrial and aquatic ecosystems. They include the green algae, which are primarily aquatic, and the land plants (embryophytes), which emerged from within them. Green algae traditionally excludes the land plants, rendering them a paraphyletic group. However it is accurate to think of land plants as a kind of alga. Since the realization that the embryophytes emerged from within the green algae, some authors are starting to include them. They have cells with cellulose in their cell walls, and primary chloroplasts derived from endosymbiosis with cyanobacteria that contain chlorophylls a and b and lack phycobilins. Corroborating this, a basal phagotroph archaeplastida group has been found in the Rhodelphydia.

<span class="mw-page-title-main">Charophyceae</span> Class of algae

Charophyceae is a class of charophyte green algae. AlgaeBase places it in division Charophyta. Extant (living) species are placed in a single order Charales, commonly known as "stoneworts" and "brittleworts". Fossil members of the class may be placed in separate orders, e.g. Sycidiales and Trochiliscales.

<span class="mw-page-title-main">Photosynthetic picoplankton</span> Group of photosynthetic plankton

Photosynthetic picoplankton or picophytoplankton is the fraction of the photosynthetic phytoplankton of cell sizes between 0.2 and 2 μm. It is especially important in the central oligotrophic regions of the world oceans that have very low concentration of nutrients.

Phycodnaviridae is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid. As of 2014, there were 33 species in this family, divided among 6 genera. This family belongs to a super-group of large viruses known as nucleocytoplasmic large DNA viruses. Evidence was published in 2014 suggesting that specific strains of Phycodnaviridae might infect humans rather than just algal species, as was previously believed. Most genera under this family enter the host cell by cell receptor endocytosis and replicate in the nucleus. Phycodnaviridae play important ecological roles by regulating the growth and productivity of their algal hosts. Algal species such Heterosigma akashiwo and the genus Chrysochromulina can form dense blooms which can be damaging to fisheries, resulting in losses in the aquaculture industry. Heterosigma akashiwo virus (HaV) has been suggested for use as a microbial agent to prevent the recurrence of toxic red tides produced by this algal species. Phycodnaviridae cause death and lysis of freshwater and marine algal species, liberating organic carbon, nitrogen and phosphorus into the water, providing nutrients for the microbial loop.

Ostreococcus is a genus of unicellular coccoid or spherically shaped green algae belonging to the class Mamiellophyceae. It includes prominent members of the global picoplankton community, which plays a central role in the oceanic carbon cycle.

<i>Micromonas</i> Genus of algae

Micromonas is a genus of green algae in the family Mamiellaceae.

<i>Nephroselmis</i> Genus of algae

Nephroselmis is a genus of green algae. It has been placed in the family Nephroselmidaceae, although a 2009 study suggests that it should be separated into its own class, Nephroselmidophyceae. One species can be an endosymbiont of Hatena arenicola.

<i>Prasinoderma</i> Genus of algae

Prasinoderma is a genus of green algae in the phylum Prasinodermophyta. Both species in the genus are unicellular, but P. coloniale forms loose sticky colonies.

The Mesostigmatophyceae are a class of basal green algae found in freshwater. In a narrow circumscription, the class contains a single genus, Mesostigma. AlgaeBase then places the order within its circumscription of Charophyta. A clade containing Chlorokybus and Spirotaenia may either be added, or treated as a sister, with Chlorokybus placed in a separate class, Chlorokybophyceae. When broadly circumscribed, Mesostigmatophyceae may be placed as sister to all other green algae, or as sister to all Streptophyta.

<span class="mw-page-title-main">Picoeukaryote</span> Picoplanktonic eukaryotic organisms 3.0 μm or less in size

Picoeukaryotes are picoplanktonic eukaryotic organisms 3.0 μm or less in size. They are distributed throughout the world's marine and freshwater ecosystems and constitute a significant contribution to autotrophic communities. Though the SI prefix pico- might imply an organism smaller than atomic size, the term was likely used to avoid confusion with existing size classifications of plankton.

<i>Ostreococcus tauri</i> Species of alga

Ostreococcus tauri is a unicellular species of marine green alga about 0.8 micrometres (μm) in diameter, the smallest free-living (non-symbiotic) eukaryote yet described. It has a very simple ultrastructure, and a compact genome.

<i>Prasinovirus</i> Genus of viruses

Prasinovirus is a genus of large double-stranded DNA viruses, in the family Phycodnaviridae that infect phytoplankton in the Prasinophyceae. There are three groups in this genus, including Micromonas pusilla virus SP1, which infects the cosmopolitan photosynthetic flagellate Micromonas pusilla.

<span class="mw-page-title-main">Phragmoplastophyta</span> Clade of algae

The Phragmoplastophyta are a proposed sister clade of the Klebsormidiaceae in the Streptophyte/Charophyte clade. The Phragmoplastophyta consist of the Charophyceae and another unnamed clade which contains the Coleochaetophyceae, Zygnematophyceae, Mesotaeniaceae, and Embryophytes. It is an important step in the emergence of land plants within the green algae. It is equivalent to the ZCC clade/grade, cladistically granting the Embryophyta.

<span class="mw-page-title-main">Prasinodermophyta</span>

The marine Prasinodermophyta are a proposed basal Viridiplantae clade, as sister of another clade comprising the Chlorophyta and the Streptophyta. It consists of the Prasinodermophyceae and the Palmophyllophyceae. They were previously considered to be a basal Chlorophyta clade, or part of the "Prasinophytes".

<span class="mw-page-title-main">Chloropicaceae</span> Class of green algae

Chloropicophyceae is a class of green algae in the division Chlorophyta that, along with Picocystophyceae, coincides with the traditional "prasinophyte clade VII". Chloropicophyceae has a single order, Chloropicales with a single family, Chloropicaceae.

References

  1. 1 2 Lopes Dos Santos A, Pollina T, Gourvil P, Corre E, Marie D, Garrido JL, Rodríguez F, Noël MH, Vaulot D, Eikrem W (October 2017). "Chloropicophyceae, a new class of picophytoplanktonic prasinophytes". Scientific Reports. 7 (1): 14019. Bibcode:2017NatSR...714019L. doi:10.1038/s41598-017-12412-5. PMC   5656628 . PMID   29070840.
  2. ↑ Linzhou Li; Sibo Wang; Hongli Wang; Sunil Kumar Sahu; Birger Marin; Haoyuan Li; Yan Xu; Hongping Liang; Zhen Li; Shifeng Chen; Tanja Reder; Zehra Çebi; Sebastian Wittek; Morten Petersen; Barbara Melkonian; Hongli Du; Huanming Yang; Jian Wang; Gane Ka-Shu Wong; Xun Xu; Xin Liu; Yves Van de Peer; Michael Melkonian; Huan Liu (22 June 2020). "The genome of Prasinoderma coloniale unveils the existence of a third phylum within green plants". Nature Ecology & Evolution. 4 (9): 1220–1231. doi:10.1038/s41559-020-1221-7. PMC   7455551 . PMID   32572216.
  3. 1 2 3 Sym, S. D. and Pienaar, R. N. 1993. The class Prasinophyceae. In Round, F. E. and Chapman, D. J. (eds) Progress in Phycological Research, Vol. 9. Biopress Ltd., Bristol, pp. 281-376.
  4. 1 2 3 4 Leliaert F, Verbruggen H, Zechman FW (September 2011). "Into the deep: new discoveries at the base of the green plant phylogeny". BioEssays. 33 (9): 683–92. doi:10.1002/bies.201100035. PMID   21744372. S2CID   40459076.
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  9. ↑ Mixotrophy in the Antarctic phytoflagellate, Pyramimonas gelidicola (Chlorophyta: Prasinophyceae)
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  27. ↑ Leliaert F, Tronholm A, Lemieux C, Turmel M, DePriest MS, Bhattacharya D, Karol KG, Fredericq S, Zechman FW, Lopez-Bautista JM (May 2016). "Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov". Scientific Reports. 6 (1): 25367. Bibcode:2016NatSR...625367L. doi:10.1038/srep25367. PMC   4860620 . PMID   27157793.
  28. ↑ Linzhou Li; Sibo Wang; Hongli Wang; Sunil Kumar Sahu; Birger Marin; Haoyuan Li; Yan Xu; Hongping Liang; Zhen Li; Shifeng Chen; Tanja Reder; Zehra Çebi; Sebastian Wittek; Morten Petersen; Barbara Melkonian; Hongli Du; Huanming Yang; Jian Wang; Gane Ka-Shu Wong; Xun Xu; Xin Liu; Yves Van de Peer; Michael Melkonian; Huan Liu (22 June 2020). "The genome of Prasinoderma coloniale unveils the existence of a third phylum within green plants". Nature Ecology & Evolution. 4 (9): 1220–1231. doi: 10.1038/s41559-020-1221-7 . PMC   7455551 . PMID   32572216.
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