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“Amazed” researchers: Mitochondria found that produce energy without any DNA

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The life form is a dinoflagellate, a marine plankton parasite. From ScienceDaily:

The mitochondria of the dinoflagellate Amoebophrya ceratii appear to produce energy just like our own mitochondria, but without any genetic material, as the team reports in the journal Science Advances. …

In this context, the team sequenced the genome (all the genetic material) of Amoebophrya, which consists of roughly 100 million base pairs. That’s extremely low by dinoflagellate standards: other species have genome a thousand times larger, which is much larger than even the human genome. That being said, a small genome isn’t exactly unusual for a parasite. Many of those pursuing this lifestyle don’t produce all of the metabolic products they need to survive; they simply steal them from their host. Though this makes them host-dependent, it also means there are many genes they can simply do without. But that’s not the road that Amoebophrya ceratii chose to go down. “In this species, nearly all metabolic processes still work, so it should also be able to get by quite well on its own,” says Uwe John. And it can do so with significantly less genetic material than any other dinoflagellate.

This reduction is especially pronounced in that part of the genome that lies outside the nucleus. In plants and algae, their own DNA is not just found in the nucleus and mitochondria, but also in the plastids, which they need for photosynthesis. For dinoflagellates in general, this plastid DNA is fairly basic, and consists of only 14 genes. Yet Amoebophrya ceratii would appear to have done away with the plastids entirely, and with all but one of their genes.

Yet the ‘budget cuts’ that the parasite has pursued with regard to its mitochondria are even more impressive. In related species, these tiny power plants’ DNA still contains three genes, which experts have generally assumed to be indispensable. But Amoebophrya ceratii has apparently cut out the mitochondria genome entirely; despite painstaking efforts, the team was unable to find any trace of it. Two of the three genes are nowhere to be found, and the third, cytochrome c oxidase 1 (COX1 or COI), has migrated to the nucleus. “That absolutely amazed me,” says Uwe John, “because there’s no other oxygen-breathing life-form on record that has no genetic material of its own in its mitochondria.”

This downsizing could come in handy when the parasites need to rapidly form a large number of new dinospores… Paper. (open access) – Uwe John, Yameng Lu, Sylke Wohlrab, Marco Groth, Jan Janouškovec, Gurjeet S. Kohli, Felix C. Mark, Ulf Bickmeyer, Sarah Farhat, Marius Felder, Stephan Frickenhaus, Laure Guillou, Patrick J. Keeling, Ahmed Moustafa, Betina M. Porcel, Klaus Valentin, Gernot Glöckner. An aerobic eukaryotic parasite with functional mitochondria that likely lacks a mitochondrial genome. Science Advances, 2019; 5 (4): eaav1110 DOI: 10.1126/sciadv.aav1110 More.

Does anyone remember when genes were still a “thing”?

The researchers go on to speculate as to how, despite appearances, not having any mitochondrial DNA is an evolutionary advantage. But wait a minute. Maybe it isn’t. A large proportion of the types of life forms that have ever existed are extinct. Insisting on explanations that show how a given change is an example of fitness created by natural selection requires us to ignore the possibility that the life form may, in fact, be on the way out. As Colin Patterson used to say, we don’t know why most extinctions occur. As long as we keep mapping genomes, we are sure to find more odd stuff.

Maybe the next time something happens that requires the use of mitochondrial DNA, that particular species will disappear. No, we don’t know that but neither do the researchers know that whatever we find is an example of fitness. One wishes they felt free to say, maybe not. Time will tell.


See also: Researcher: “No Rhyme Or Reason” To Unexpected Sea Anemone Genome

Two Jellyfish Genomes Differ “As Drastically As Humans Do From Sea Urchins.

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I can only imaging how much time and resources ET has to waste.
You are a waste of skin and bones. Your entire life is a waste... ET
BB, I do have a little time to waste, which is why I'm trading comments with you. ;) Andrew asauber
It’s likely they are wasting a lot of time and resources.
They certainly would be if they cam over here. It's a good thing that I have plenty of time and resources to waste. You must as well. I can only imaging how much time and resources ET has to waste. :) Brother Brian
"They are too busy doing real research." It's likely they are wasting a lot of time and resources. Andrew asauber
If they had the stones to come here and be rightly criticized, I would.
They are too busy doing real research. Brother Brian
"Tell that to the thousands of researchers who use it in the same context I have." If they had the stones to come here and be rightly criticized, I would. Andrew asauber
Well it doesn’t take too much brain power to understand that you shouldn’t use the word “strategy” when there is no strategy involved.
Tell that to the thousands of researchers who use it in the same context I have. Theology and philosophy also use terms that have a different meaning to the general public. Do you criticize them when they use terms like "truth" when it is used in a different context than what the general public uses it. Brother Brian
BB, Well it doesn't take too much brain power to understand that you shouldn't use the word "strategy" when there is no strategy involved. Andrew asauber
Interesting little critter. Mitochondrial DNA typically is responsible for producing a small number of proteins necessary for the proper functioning of the cell. However, if the nuclear DNA is producing these proteins, or comparable proteins with respect to function, there is probably no necessity for the mitochondria to have DNA. A bigger question is how this critter came to a situation where these proteins were produced by the nuclear DNA. Did the necessary genes, as the article suggests, move from the mitochondria to the nucleus? Did the nucleus always have these genes? Did they develop and become fixed via drift and/or selection? The fact that this strategy has only been found in one organism so far suggests that whatever pathway it took was either a very complex one or a very unlikely one. OK, now people can pick on me for using the word "strategy". Brother Brian

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