Photoinhibition atlas of photosynthetic sea slugs

V. HAVURINNE, L. MORELLI, P. CARTAXANA, S. CRUZ

Edifício ECOMARE, Universidade de Aveiro, Estrada do Porto de Pesca, 3830-565 Gafanha da Nazaré, Ilhavo, Portugal

Anyone who has ever isolated intact chloroplasts can tell that they are fickle organelles that do not last long after isolation. Sacoglossan sea slugs do not share this experience, as some of them can isolate chloroplasts from their prey algae and incorporate them intracellularly as new foreign organelles – kleptoplasts. Separated from the algal nucleus and in the face of light induced damage, kleptoplasts challenge the paradigms of photosynthesis by remaining active inside the slugs for months. There is currently no definitive explanation to this phenomenon known to exist in several species of sacoglossans that incorporate the chloroplasts from different algal species. We measured the kinetics of photoinhibition, the irreversible damage to photosystem II (PSII), under high light in multiple combinations of photosynthetic slugs and their prey algae to understand how much the resilience against photoinhibition contributes to the overall longevity of the kleptoplasts. Out of all the tested slugs, Elysia timida is the only species that eats only one alga, Acetabularia acetabulum, and it was also by far the best species in terms of protecting kleptoplasts from photoinhibition. The molecular mechanisms behind the remarkable photoprotection in E. timida are currently under investigation.