Kleptoplasty

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Electron micrograph
: scale bar is 3 µm.

Kleptoplasty or kleptoplastidy is a process in

thief. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily continuing photosynthesis
and benefiting the host.

Etymology

The word kleptoplasty is derived from Ancient Greek κλέπτης (kléptēs), meaning 'thief', and πλαστός (plastós), originally meaning formed or moulded, and used in biology to mean a plastid.[1]

Process

Kleptoplasty is a process in symbiotic relationships whereby plastids, notably chloroplasts from algae, are sequestered by the host. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily continuing photosynthesis and benefiting the host.[1] The term was coined in 1990 to describe chloroplast symbiosis.[2][3]

Taxonomic range

Kleptoplasty occurs in two major clades of eukaryotes, namely micro-organisms of the SAR supergroup, and some marine animals.

Eukaryota

SAR supergroup

Foraminifera

Some species of the foraminiferan genera Bulimina, Elphidium, Haynesina, Nonion, Nonionella, Nonionellina, Reophax, and Stainforthia sequester diatom chloroplasts.[4]

Alveolata

Dinoflagellates

The stability of transient plastids varies considerably across plastid-retaining species. In the

Pfisteria piscicida, kleptoplastids are photosynthetically active for only a few days, while kleptoplastids in Dinophysis spp. can be stable for 2 months.[1] In other dinoflagellates, kleptoplasty has been hypothesized to represent either a mechanism permitting functional flexibility, or perhaps an early evolutionary stage in the permanent acquisition of chloroplasts.[5]

Ciliates
Mesodinium rubrum

Geminigera cryophila.[6] M. rubrum participates in additional endosymbiosis by transferring its plastids to its predators, the dinoflagellate planktons belonging to the genus Dinophysis.[7]

Karyoklepty is a related process in which the nucleus of the prey cell is kept by the host as well. This was first described in 2007 in M. rubrum.[8]

Animals

Rhabdocoel flatworms

Two species of rhabdocoel marine flatworms, Baicalellia solaris and Pogaina paranygulgus, make use of kleptoplasty. The group was previously classified as having algal endosymbionts, though it was already discovered that the endosymbionts did not contain nuclei.[9]

While consuming diatoms, B. solaris and P. paranygulus, in a process not yet discovered, extract plastids from their prey, incorporating them subepidermally, while separating and digesting the frustule and remainder of the diatom. In B. solaris the extracted plastids, or kleptoplasts, continue to exhibit functional photosynthesis for a short period of roughly 7 days. As the two groups are not sister taxa, and the trait is not shared among groups more closely related, there is evidence that kleptoplasty evolved independently within the two taxa.[10]

Sea slugs (gastropods)

Sacoglossa
Costasiella kuroshimae, a Sacoglossan sea slug which uses kleptoplasty to create complex patterns on its body

diverticula. The longest known kleptoplastic association, which can last up to ten months, is found in Elysia chlorotica,[2] which acquires chloroplasts by eating the alga Vaucheria litorea, storing the chloroplasts in the cells that line its gut.[12] Juvenile sea slugs establish the kleptoplastic endosymbiosis when feeding on algal cells, sucking out the cell contents, and discarding everything except the chloroplasts. The chloroplasts are phagocytosed by digestive cells, filling extensively branched digestive tubules, providing their host with the products of photosynthesis.[13] It is not resolved, however, whether the stolen plastids actively secrete photosynthate or whether the slugs profit indirectly from slowly degrading kleptoplasts.[14]

Due to this unusual ability, the sacoglossans are sometimes referred to as "solar-powered sea slugs," though the actual benefit from photosynthesis on the survival of some of the species that have been analyzed seems to be marginal at best.[15] In fact, some species may even die in the presence of the carbon dioxide-fixing kleptoplasts as a result of elevated levels of reactive oxygen species.[16]

Changes in temperature have been shown to negatively affect kleptoplastic abilities in sacoglossans. Rates of photosynthetic efficiency as well as kleptoplast abundance have been shown to decrease in correlation to a decrease in temperature. The patterns and rate of these changes, however, varies between different species of sea slug.[17]

Nudibranchia

Some species of another group of sea slugs, nudibranchs such as Pteraeolidia ianthina, sequester whole living symbiotic zooxanthellae within their digestive diverticula, and thus are similarly "solar-powered".[18]

See also

References

  1. ^
    PMID 18518896
    .
  2. ^
    S2CID 9671982
    . Retrieved 2008-11-24.
  3. S2CID 87182226
    .
  4. doi:10.1016/s0012-8252(99)00017-3
    .
  5. PMID 17227410
    .
  6. S2CID 4410812
    .
  7. PMID 20305031
    .
  8. S2CID 4410812
    . Retrieved 4 February 2015.
  9. ^ E. Marcus, Turbellaria Brasileiros (9). Bol. Fac. Fil. Ci. Letras Univ. São Paulo 16, 5–215 (1951).
  10. PMID 31328166
    .
  11. PMID 19951407
    .
  12. ^ Catherine Brahic (24 November 2008). "Solar-powered sea slug harnesses stolen plant genes". New Scientist. Retrieved 24 November 2008.
  13. ^ "SymBio: Introduction-Kleptoplasty". University of Maine. Archived from the original on 2008-12-02. Retrieved 2008-11-24.
  14. PMID 24767983
    .
  15. ISSN 2083-9480
    .
  16. PMID 25652835
    .
  17. PMID 29760759
    .
  18. ^ Sutton & Hoegh-Guldberg, Host-Zooxanthella Interactions in Four Temperate Marine Symbioses; Assessment of Effect of Host Extract on Symbionts; The Biological bulletin, Marine Biological Laboratory (Woods Hole, Mass.). v. 178 (1990) p. 175

External links

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