Photosynthesizing sea slug borrows key gene from algae

A bright green sea slug known as the eastern emerald elysia (Elysia chlorotica) might as well be a plant. It's got the hue of spring, and a body that mimics a leaf. And as new research reveals, it even boasts plant genes, borrowed from the algae it eats.
Researchers at the Marine Biological Laboratory, a research center in Massachusetts, were able to use advanced imaging techniques to locate a chromosome swiped from digested algae in the sea slug's DNA.
The borrowed genes explain why the emerald elysia is able to go without traditional food for several months -- relying instead on chloroplasts swiped from the alga Vaucheria litorea to turn sunlight into nutrients.
Scientists have understand that this particular species of sea slug, found up and down the Eastern Seaboard, copped the algae's photosynthesis via chloroplasts, but they weren't entirely sure how. The discovery of this new stolen gene, however, helps scientists better understand how the chloroplasts survive and function for so long inside the slug's own digestive cells.
"This paper confirms that one of several algal genes needed to repair damage to chloroplasts, and keep them functioning, is present on the slug chromosome," study author Sidney K. Pierce explained in a press release.
"The gene is incorporated into the slug chromosome and transmitted to the next generation of slugs," Pierce added. "While the next generation must take up chloroplasts anew from algae, the genes to maintain the chloroplasts are already present in the slug genome."
The sea slug is one of the few examples of genetic transfer among multicellular organisms, and researchers say the mechanism the enables such a transfer could have applications in medicine.
"Is a sea slug a good [biological model] for a human therapy? Probably not," Pierce said. "But figuring out the mechanism of this naturally occurring gene transfer could be extremely instructive for future medical applications."
The study was published last month in the journal The Biological Bulletin.