Cortical alveolum

Transmission electron micrograph of a thin section of the surface of the ciliate Paramecium putrinum, showing the alveoli (red arrows) under the cell surface

The cortical alveolum (pl. cortical alveoli) is a cellular organelle consisting of a vesicle located under the cytoplasmic membrane, to which they give support. The term "corticate" comes from an evolutionary hypothesis about the common origin of kingdoms Plantae and Chromista, because both kingdoms have cortical alveoli in at least one phylum. At least three protist lineages exhibit these structures: Telonemia, Alveolata and Glaucophyta.

Definition

Cortical alveoli have been defined as flattened membranous sacs or vesicles that strengthen the cellular cortex through the firm fixation to the underlying membrane and microtubules.[1] They typically form a continuous layer that acts as a flexible film, although they can also constitute a semi-rigid structure or the scales of a theca.[2]

Occurrence

Cortical alveoli are the defining cellular characteristic of the protist clade Alveolata, otherwise united solely by molecular phylogeny.[3] The name 'Alveolata' is a reference to this trait,[4][1] present in all representatives of this group: the parasitic apicomplexans and perkinsozoans,[5] the predatory ciliates[2] and colpodellids,[6][7] the chromerid algae,[8][9] and the ecologically diverse dinoflagellates,[10] as well as small basal flagellates collectively known as colponemids.[11] A small phylum of eukaryotes, Telonemia, contains flagellated species that exhibit flattened alveoli, much like in Alveolata. Both groups share evolutionary affinity, comprising the TSAR supergroup along with Stramenopiles and Rhizaria.[12]

In addition to the TSAR supergroup, the Archaeplastida supergroup contains a lineage of algae with cortical alveoli, known as Glaucophyta. All species of glaucophytes exhibit flattened membranous alveoli lying immediately below the plasma membrane, in every region of the cell except for the flagellar furrow. In addition, these alveoli may contain rigid plates that, similarly to thecate dinoflagellates, define the shape of the otherwise amorphous cell.[13] The common morphological trait with alveolates has been used to propose a common evolutionary origin between the kingdoms Plantae (defined as Archaeplastida) and Chromista (containing alveolates).[14] This is known as the "corticate" hypothesis, postulated by protozoologist Thomas Cavalier-Smith,[15][16] but later rejected due to the non-monophyly of kingdom Chromista.[17] Instead, both Archaeplastida and the TSAR supergroup are united in a clade known as Diaphoretickes, which contains the remaining chromist groups Haptista and Cryptista.[17][4]

Function

Although cortical alveoli are very diverse in shape and function among the different groups of protists, they always share the function of supporting the cytoplasmic membrane. In the case of apicomplexan parasites, they're related to the mobility and facilitate the invasion of host cells, and thus they have a considerable importance in medicine. In dinoflagellates the alveoli contain cellulose and compose the scales of their armor. Lastly, in ciliates they are part of the cortical complex that supports the extrusomes, the basal bodies of the cilia and the intricate cortical shell.[18]

References

1. Cavalier-Smith, Thomas (2017). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma. 255 (1): 297–357. doi:10.1007/s00709-017-1147-3. PMC 5756292. PMID 28875267.
2. Stelly N, Mauger JP, Claret M, Adoutte A (1991). "Cortical alveoli of Paramecium: a vast submembranous calcium storage compartment" (PDF). The Journal of Cell Biology. 113 (1): 103–112. doi:10.1083/jcb.113.1.103. PMID 1848863. S2CID 2395284.
3. Keeling PJ; Burger G; Durnford DG; Lang BF; Lee RW; Pearlman RE; Roger AJ; Gray MW (December 2005). "The tree of eukaryotes". Trends in Ecology & Evolution. 20 (12): 670–6. doi:10.1016/J.TREE.2005.09.005. ISSN 0169-5347. PMID 16701456. Wikidata Q29616064.
4. Adl, et al. (2012). "The revised classification of eukaryotes". Journal of Eukaryotic Microbiology. 59 (5): 429–514. doi:10.1111/j.1550-7408.2012.00644.x. PMC 3483872. PMID 23020233.
5. Esther Garcés; Mona Hoppenrath (November 2010). "Ultrastructure of the intracellular parasite Parvilucifera sinerae (Alveolata, Myzozoa) infecting the marine toxic planktonic dinoflagellate Alexandrium minutum (Dinophyceae)". Harmful Algae. 10 (1): 64–70. doi:10.1016/J.HAL.2010.07.001. ISSN 1568-9883. Wikidata Q62109160.
6. Brian S Leander; Olga N Kuvardina; Vladimir V Aleshin; Alexander P Mylnikov; Patrick John Keeling (1 September 2003). "Molecular phylogeny and surface morphology of Colpodella edax (Alveolata): insights into the phagotrophic ancestry of apicomplexans". Journal of Eukaryotic Microbiology. 50 (5): 334–340. doi:10.1111/J.1550-7408.2003.TB00145.X. ISSN 1066-5234. PMID 14563171. Wikidata Q34270501.
7. A. P. Mylnikov (1 November 2009). "Ultrastructure and Phylogeny of Colpodellids (Colpodellida, Alveolata)". Russian Academy of Sciences. Biology Bulletin (6): 685–694. ISSN 1062-3590. PMID 20143628. Wikidata Q82839650.
8. Moore RB; Oborník M; Janouskovec J; Chrudimský T; Vancová M; Green DH; Wright SW; Davies NW; et al. (February 2008). "A photosynthetic alveolate closely related to apicomplexan parasites". Nature. 451 (7181): 959–963. Bibcode:2008Natur.451..959M. doi:10.1038/nature06635. PMID 18288187. S2CID 28005870.
9. John M Archibald (1 January 2009). "The puzzle of plastid evolution". Current Biology. 19 (2): R81-8. doi:10.1016/J.CUB.2008.11.067. ISSN 0960-9822. PMID 19174147. Wikidata Q33346647.
10. Mona Hoppenrath (29 April 2016). "Dinoflagellate taxonomy — a review and proposal of a revised classification". Marine Biodiversity. 47 (2): 381–403. doi:10.1007/S12526-016-0471-8. ISSN 1867-1616. Wikidata Q112831588.
11. Jan Janouškovec; Denis Tikhonenkov; Kirill Mikhailov; Timur Simdyanov; Vladimir V. Aleoshin; Alexander P Mylnikov; Patrick John Keeling (5 December 2013). "Colponemids represent multiple ancient alveolate lineages". Current Biology. 23 (24): 2546–2552. doi:10.1016/J.CUB.2013.10.062. ISSN 0960-9822. PMID 24316202. Wikidata Q35062245.
12. Tikhonenkov, Denis V.; Jamy, Mahwash; Borodina, Anastasia S.; Belyaev, Artem O.; Zagumyonnyi, Dmitry G.; Prokina, Kristina I.; Mylnikov, Alexander P.; Burki, Fabien; Karpov, Sergey A. (2022). "On the origin of TSAR: morphology, diversity and phylogeny of Telonemia". Open Biology. 12 (3). The Royal Society. doi:10.1098/rsob.210325. ISSN 2046-2441. PMC 8924772. PMID 35291881.
13. Aaron A Heiss; Alaric W Heiss; Kaleigh Lukacs; Eunsoo Kim (11 September 2017). "The flagellar apparatus of the glaucophyte Cyanophora cuspidata". Journal of Phycology. 53 (6): 1120–1150. doi:10.1111/JPY.12569. ISSN 0022-3646. PMID 28741699. Wikidata Q38368966.
14. T Cavalier-Smith (March 2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International Journal of Systematic and Evolutionary Microbiology. 52 (2): 297–354. doi:10.1099/00207713-52-2-297. ISSN 1466-5026. PMID 11931142. Wikidata Q28212529.
15. Thomas Cavalier-Smith (23 June 2010). "Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree". Biology Letters. 6 (3): 342–5. doi:10.1098/RSBL.2009.0948. ISSN 1744-9561. PMC 2880060. PMID 20031978. Wikidata Q24601474.
16. Cavalier-Smith, Thomas; Chao, Ema E.; Lewis, Rhodri (December 2015). "Multiple origins of Heliozoa from flagellate ancestors: New cryptist subphylum Corbihelia, superclass Corbistoma, and monophyly of Haptista, Cryptista, Hacrobia and Chromista". Molecular Phylogenetics and Evolution. 93 (1): 331–362. doi:10.1016/j.ympev.2015.07.004. PMID 26234272.
17. Fabien Burki; Andrew J Roger; Matthew W Brown; Alastair G B Simpson (9 October 2019). "The New Tree of Eukaryotes". Trends in Ecology & Evolution. 35 (1): 43–55. doi:10.1016/J.TREE.2019.08.008. ISSN 0169-5347. PMID 31606140. Wikidata Q90670033.
18. Gould SB, Tham WH, Cowman AF, McFadden GI, Waller RF (2008). "Alveolins, a new family of cortical proteins that define the protist infrakingdom Alveolata". Molecular Biology and Evolution. 25 (6): 1219–1230. doi:10.1093/molbev/msn070. PMID 18359944.