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Photosynthesizing Sea Slugs Steal Genes From Algae
An anonymous reader writes For decades, scientists have puzzled over how a certain sea slug acquires the ability to photosynthesize after ingesting algae. An advanced imaging technique now confirms that the slugs are literally stealing genes from the algae. It's considered the first example of horizontal gene transfer in a multicellular organism.
The slugs at some point in their past acquired the genes from algae that are required to maintain/repair the chloroplasts that each one collects from the algae they eat. The horizontal gene transfer is (presumably) not an ongoing process but something that happened in their distant past.
The baby slugs start eating algae and they digest most of them but they save the chloroplasts from the algae cells and integrate them into their own tissue. Once they accumulate enough of them they basically become solar powered and don't need to eat anymore.
Normally the chloroplasts would not survive very long without an algae around them to take care of them, but this is where the genes that the slug has that originally came from the algae come into play. The slug is thus able to provide the things that its adopted chloroplasts need to survive for many months.
Definitely very cool.
G.
It might be pointed out that plants' chloroplasts and our mitochondria are now well-understood to have originated as "ingested" bacteria that, rather than being broken down and digested, ended up first as internal symbionts, and were over time transformed into the cells' internal organs. What these slugs are doing is somewhat similar to this, though on a somewhat smaller scale. The slugs apparently only nab a few chromosomes from the algae, and transfer them into their own digestive-system cells.
But the "first" in the article is a bit different from this: They describe it as the first-known such transfer between two multi-cellular species. Our mitochondria seem to have originated in a single-cell ancestor similar to an amoeba, which incorporated an entire living bacterium as an internal resident. Similarly, plant chloroplasts are believed to have originated as photosynthetic bacteria that were incorporated whole into early algae. In both of these cases, there has been gene transfer from the internal bacteria into the eukaryotic cell's nucleus, leaving the mitochondria and chloroplasts with mostly just the genes needed to do their job, and unable to survive outside their host cell.
But the slugs took a different route, of separating out the photosynthesis genes from their food's cells, moving the DNA into the slugs' cells, and digesting the rest of the algal cells as food.
It could be interesting to stick around and see how this works out. Eventually, they might be able to incorporate the photosynthetic mechanism into their own genome, so that when a slug cell divides, it'll get copies of of these genes and won't have to steal them from algae. Plants never never did this, because they maintained their chloroplasts' ability to divide within the plant cell (with a bit of help from the host cell). The slug's approach might turn out better than the plants'. Or maybe it won't. Or maybe it'll just be two different approaches to photosynthesis that both work well enough.
But we might not know about this for a few more millennia ...
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Erm... Monsanto GM modifications are open source. The sequence of nucleotides and the method of their insertion is clearly described in these patents: https://www.google.com/patents... , https://www.google.com/patents... and other related patents. Feel free to use them, they are expired as of the last year.