Elysia chlorotica - photosynthetic sea slug movie 2

The sea slug Elysia chlorotica acquires plastids by ingestion of its algal food source Vaucheria litorea. Organelles are sequestered in the mollusc's digestive epithelium, where they photosynthesize for months in the absence of algal nucleocytoplasm. This is perplexing because plastid metabolism depends on the nuclear genome for more than 90% of the needed proteins. Two possible explanations for the persistence of photosynthesis in the sea slug are (i) the ability of V. litorea plastids to retain genetic autonomy and/or (ii) more likely, the mollusc provides the essential plastid proteins. Under the latter scenario, genes supporting photosynthesis have been acquired by the animal via horizontal gene transfer and the encoded proteins are retargeted to the plastid. We sequenced the plastid genome and confirmed that it lacks the full complement of genes required for photosynthesis. In support of the second scenario, we demonstrated that a nuclear gene of oxygenic photosynthesis, psbO, is expressed in the sea slug and has integrated into the germline. The source of psbO in the sea slug is V. litorea because this sequence is identical from the predator and prey genomes. Evidence that the transferred gene has integrated into sea slug nuclear DNA comes from the finding of a highly diverged psbO 3' flanking sequence in the algal and mollusc nuclear homologues and gene absence from the mitochondrial genome of E. chlorotica. We demonstrate that foreign organelle retention generates metabolic novelty ("green animals") and is explained by anastomosis of distinct branches of the tree of life driven by predation and horizontal gene transfer.

http://www.ncbi.nlm.nih.gov/pubmed/19004808

Category:

Science & Technology

Tags:

• sea
• slug
• elysia
• photosynthesis
• brown
• algae
• Vaucheria
• endosymbiosis
• gene
• transfer

[eBiology]

This is a beautiful example of how endosymbiosis (at least one phase) is a precursor to the evolution of multicellular organisms from unicellular organisms.

[pulgamatona]

@Intricate9041

A gene needed for the photosintesis (psbO) has been found on Elysia chlorotica's genome. That may be proof of the early stages of evolutive endocitosis as well as the reason why those cloroplasts can stay "alive" inside the slug.

[0redthunder0]

I want one as a pet :P

[Dorskfr]

I WANT TO EAT THAT ALGEA

[Intricate9041]

@osirisstar It doesn't take over the genes of the chloroplasts does it? It just incorporates them into it's own body much like we incorporated mitochondria in our cells millions of years ago (the small cell organs that help us with the production of energy out of cellulose). The DNA of the mitochondria still differs from ours if I'm not mistaken (cross-referencing my rambling is advisable ;))

Anyway, it's still an amazing example of symbiosis on a cellular level

[llGemini]

Evolution at its very Best!

[LanesAccount]

its life must get kinda boring after it gets enough chloroplasts into its gut.. just chills like a leaf in the sun.. wat kind of new technology could this spawn in the future?"

[osirisstar]

Really changes the meaning of "you are what you eat". Evolution by digestion is something that makes sense epigenetically but permanent gene transfers is incredible.

[tiarefl]

¡ Fascinante animal-planta !

[trekmogui]

That is just amazing!

How does Evolution explain it?

so cool!

Hope Dawkins talk about it later!