Chromera
| Chromera veli | |
|---|---|
| Scientific classification | |
| Domain: | |
| Kingdom: | |
| Superphylum: | |
| Genus: | Chromera
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| Species: | Chromera velia
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Chromera velia, also known as a "chromerid",[1] is a photosynthetic alga[2] in the superphylum Alveolata.
It has typical features of alveolates, being phylogenetically related to apicomplexa, and contains a photosynthetic plastid and the C. velia uses this organelle as the primary energy source, thus being the only known autotrophic apicomplexan. But it still retains a pseudo-symbiotic relationship with the coral reef around it.[3]
History
Chromera velia was first discovered and isolated by Robert B. Moore (former PhD student from Dee Carter Lab, University of Sydney) during the collection of Stony corals (Scleractinia, Cnidaria) Plesiastrea versipora (Faviidae) from Sydney Harbour, New South Wales, Australia by Thomas Starke-Peterkovic and Les Edwards in December 2001. The same novel unicellular alga was also found in Leptastrea purpurea (Faviidae) from One Tree Island Great Barrier Reef, Queensland, Australia by Karen Miller and Craig Mundy in November 2001.[3]
Special features of C. velia plastid
Plastid of the Chromera velia has 4 membranes and contains chlorophyll a, however, chlorophyll c is missing.Unlike other eukaryotic algage which use UGG as codons for encoding tryptophan, the plastid of C. velia uses codon UGA to encode tryptophan at seven conserved position in the psbA gene. This UGA-Trp codon that is only characteristic of apicoplast plastids, and unprecedented in any photosynthetic plastid. Discovery of this organism provides a strong model to study the evolution of parasitism in Apicomplexa.[3]
Evolution
The discovery of Chromera velia and its unique plastid which is similar in origin to the apicomplexans, possesses an important link in the evolutionary history of the apicomplexans. It is hypothesized that apicomplexans, with its unique relic chloroplast organelle, were once able to synthesize energy via photosynthesis by the apicoplast. However, this autotrophic mechanism was lost and the apicomplexans has slowly evolved to become a parasitic species dependent on hosts for survival. Through a variety of phylogenetic tests on the different types of chlorophyll found in similar organisms, researchers were able to relate C. velia to dinoflagellates and apicomplexa. Previous research studies have also shown that the photosynthetic dinoflagellates, apicomplexans and C. velia share the same lineage, containing a red-algal-derived plastid. With the use of additional DNA sequencing, the relationship between C. velia, dinoflagellates and apicoplexans can be further confirmed. Genomic DNA of C. velia was extracted for PCR templates and sequences were compared with other species so as to place C. velia on a pylogenetic branch closer to the apicomplexans, thanks to the help of these biostatistical methods.[3] Although researchers are still uncertain about why apicomplexans would sacrifice their photosynthetic ability and become parasitic, it is suggested that clues might be garnered by studying the evolution of the plastid. There is still currently much debate as to the validity of C. velia phylogeny.
Importance
One of the most important aspects C. velia has to offer the greater community besides its role as a possible missing link, between the parasitic and algeal species, is its promise in the synthesis of an acting a malarial vaccine. Plasmodium falciparum, a member of the Apicomplexans, is currently the cause of 50% of all malarial infections in the world. Currently scientists have focused drug treatments on targeting the apicoplast found in the invading malarial cells. But in the laboratory setting working with apicomplexan parasites is difficult. This is mainly due to the fact they must be plated on live host cells and remain viable enough to run the necessary sequence of tests. Chromera velia, being so closely related to the parasites, may potentially be a good model to work on developing these malarial treatments. C. velia is able to live independently of animal hosts and can be grown easily and cheaply in a laboratory setting. It has also been created as single handedly putting the spotlight back on protist based research, bringing it to the forefront the various clinical and scientific applications and contributions that are possible through the study of parasites.
References
- ^ Takishita K; Yamaguchi H; Maruyama T; Inagaki Y (2009). "A hypothesis for the evolution of nuclear-encoded, plastid-targeted glyceraldehyde-3-phosphate dehydrogenase genes in "chromalveolate" members". PLoS ONE. 4 (3): e4737. doi:10.1371/journal.pone.0004737. PMC 2649427. PMID 19270733.
{{cite journal}}: Unknown parameter|author-separator=ignored (help)CS1 maint: unflagged free DOI (link) - ^ k M; Janouskovec J; Oborní Chrudimský T, Lukes J (2009). "Evolution of the apicoplast and its hosts: from heterotrophy to autotrophy and back again". Int. J. Parasitol. 39 (1): 1–12. doi:10.1016/j.ijpara.2008.07.010. PMID 18822291.
{{cite journal}}: Unknown parameter|author-separator=ignored (help); Unknown parameter|month=ignored (help) - ^ a b c d Moore RB; Oborník M; Janouskovec J; Chrudimský T; Vancová M; Green DH; Wright SW; Davies NW; Bolch CJ; Heimann K; Slapeta J; Hoegh-Guldberg O; Logsdon JM; Carter DA (2008). "A photosynthetic alveolate closely related to apicomplexan parasites". Nature. 451 (7181): 959–963. doi:10.1038/nature06635. PMID 18288187.
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