Scientists discover first organism with chlorophyll genes that doesn’t photosynthesize
by University of British Columbia
For the first time scientists have found an organism that can produce chlorophyll but does not engage in photosynthesis.
The peculiar organism is dubbed ‘corallicolid’ because it is found in 70 per cent of corals around the world and may provide clues as to how to protect coral reefs in the future.
“This is the second most abundant cohabitant of coral on the planet and it hasn’t been seen until now,” says Patrick Keeling, a University of British Columbia botanist and senior researcher overseeing the study published in Nature. “This organism poses completely new biochemical questions. It looks like a parasite, and it’s definitely not photosynthetic. But it still makes chlorophyll.”
Corallicolids live in the gastric cavity of a wide array of corals responsible for building reefs, as well as black corals, fan corals, mushroom corals, and anemones. They are an apicomplexan, part of a vast group of parasites that have a cellular compartment called a plastid, which is the part of plant and algal cells where photosynthesis takes place. The most famous apicomplexan is the parasite responsible for malaria.
More than a decade ago, photosynthetic algae related to apicomplexans were discovered in healthy corals, indicating they might have evolved from benign photosynthesising organisms attached to corals before turning into the parasites we know today.
Ecological data showed that coral reefs contain several apicomplexans, but corallicolids, the most most common one, had not been studied until now. The organism has revealed a new puzzle: not only does it have a plastid, but it contains all four plastid genes used in chlorophyll production.
So starting out as an algae, becomming a hosted organism in a commensal relationship, then transitioning to parasite, now pathogen. What an odd evolutionary trek…
‘Little brown balls’ tie malaria and algae to common ancestor
by University of British Columbia
Inconspicuous “little brown balls” in the ocean have helped settle a long-standing debate about the origin of malaria and the algae responsible for toxic red tides, according to a new study by University of British Columbia researchers.
In an article published this week in the Proceedings of the National Academy of Sciences Early Edition, UBC Botany Prof. Patrick Keeling describes the genome of Chromera and its role in definitively linking the evolutionary histories of malaria and dinoflalgellate algae.
“Under the microscope, Chromera looks like boring little brown balls,” says Keeling. “In fact, the ocean is full of little brown and green balls and they’re often overlooked in favour of more glamorous organisms, but this one has proved to be more interesting than its flashier cousins.”
First described in the journal Nature in 2008, Chromera is found as a symbiont inside corals. Although it has a compartment – called a plastid – that carries out photosynthesis like other algae and plants, Chromera is closely related to apicomplexan parasites – including malaria. This discovery raised the possibility that Chromera may be a “missing link” between the two.
So malaria is sort of an internal Red Tide… metaphorically…
Now Keeling, along with PhD candidate Jan Janouskovec, postdoctoral fellow Ales Horak and collaborators from the Czech Republic, has sequenced the plastid genome of Chromera and found features that were passed down to both apicomplexan and dinoflagellate plastids, linking the two lineages.
“These tiny organisms have a huge impact on humanity in very different ways,” says Keeling. “The tool used by dinoflagellates and Chromera to do good – symbiosis with corals – at some point became an infection mechanism for apicomplexans like malaria to infect healthy cells.