Elisabeth Hehenberger receives prestigious grant for research on the evolution of photosynthesis

The conversion of an engulfed bacterium - specifically a cyanobacterium capable of photosynthesis - into a plastid (chloroplast in plants), which is part of an eukaryotic cell, was a key moment in the evolution of life on Earth. The exact progress of this ancient process remains unclear, however, mostly because time has erased all traces. A breakthrough came with the investigation of kleptoplasty (literally "plastid stealing"), the fascinating ability of some organisms to temporarily "steal" plastids from photosynthesising cells and use them for their own benefit. "When we investigated a kleptoplastidic organism during my postdoc, we were able to provide the first evidence for a certain order of steps during plastid endosymbiosis," explains biologist Elisabeth Hehenberger, for whom this result was a turning point in her research career. She therefore decided to focus on studying these plastid-stealing organisms to help her unravel the ancient process of plastid integration.

Organisms with the ability to steal plastids are very rare. An exception are the dinoflagellates, an extremely species-rich group of single-celled microorganisms that play a key role in marine ecosystems across the world. Nevertheless, kleptoplastidic dinoflagellates are not easy to identify and so far have been discovered only by chance. Moreover, studying them is extremely difficult because of their large genomes (some have genomes that are almost 100 times larger than the human genome) and because it is challenging to keep them in laboratory conditions as their food source is often unknown.

Microscopic images of different species of dinoflagellates of the genus Dinophysis. Photo: Elisabeth Hehenberger, BC CAS

Elisabeth Hehenberger's team will search for rare dinoflagellates with these unique abilities in the seas of Sweden, Spain and Japan. The team also plans to use a recently developed imaging cell sorter, which can identify new kleptoplastidic dinoflagellates in a water sample exploiting the specific plastid colour. They will then study them using a range of cutting-edge methods and experiments to understand the process of uptake of the photosynthetic prey/algae and their transformation into a plastid. Using the newly developed hyperLOPIT method, which allows thousands of proteins to be tracked within a cell, the team will also investigate what happens to the stolen plastid itself while it is being incorporated into a new cell.

A new, undescribed species that is closely related to the Ross Sea Dinoflagellate that Elisabeth Hehenberger worked with during her postdoc in Canada. The second slide contains also a fluorescence microscopy image, which highlight the plastids that are fluorescent. Photo: Elisabeth Hehenberger, BC CAS

Thanks to ERC funding, Elisabeth Hehenberger has a unique opportunity to use her rich experience with the challenging group of dinoflagellates to elucidate a fundamental evolutionary transition. "Since this is such an important and evolutionarily old process, we are convinced that our findings will impact research on many model systems. If we understand how this process works and are able to artificially recreate it, we can influence a wide range of areas in the future, from the protection of marine ecosystems to sustainable energy production, more efficient agriculture and biofuel production," Elisabeth Hehenberger adds.