Edible second-hand solar panels

This transient endosymbiotic process, reminiscent of the primary incorporation of organelles that gave birth to eukaryotic cells, is called kleptoplasty. While it has been known for a long time, a recent study in Cell reveals intricate new details of the molecular mechanisms behind this association, which can last for a year and increase survival in case of starvation.

In the sea slug Elysia crispata, the stolen chloroplasts are highly concentrated in regulated specialized cells named plastid cells, localized around the body surface to better catch the light. The thylakoid stack ultrastructure is conserved and functional, despite the lack of the algal nuclear genome to provide needed maintenance proteins. Each chloroplast is individually wrapped in a membrane containing ATP-sensitive ion channels, forming organelles named kleptosomes, and actively kept in a functional state to produce energy in response to light. In case of prolonged starvation, a different program is activated: chloroplasts are degraded and digested. The sea slugs lose their green colour but are provided with an internal source of nutrients that can double their survival time.