Periodic Reporting for period 3 - PhotoRedesign (Redesigning the Photosynthetic Light Reactions)
Reporting period: 2023-04-01 to 2024-09-30
Photosynthesis is central to life on Earth, using energy from sunlight to make the oxygen we breathe and the food we eat. However, photosynthesis is only a few per cent efficient when you compare the energy of the sunlight that reaches a plant with the energy that ends up in the biomolecules of the plant (and even less in the parts we eat). Moreover, an analysis of plant breeding efforts over the last few decades has shown that many plant traits have already reached a state that is close to optimal for agricultural use, while photosynthesis clearly has a lot of room for improvement.
The PhotoRedesign project therefore aims to improve the efficiency of photosynthesis, and more specifically the light reactions of photosynthesis that capture light and convert the captured light energy into molecules that can then be used to convert carbon dioxide from the atmosphere into organic biomolecules. In fact, nature has invented several types of organisms capable of photosynthesis. Because they all go back to a common ancestor, these organisms are still genetically compatible, meaning that their genes also work in the other organisms. We chose three very distantly related organisms that can use very different parts of the sun's light for photosynthesis: cyanobacteria, which are blue-green, plants, which are green, and purple bacteria, which are purple. As mentioned earlier, their different colours indicate that they can use very different parts of the sun's light for photosynthesis.
Our goal is to combine the different light-harvesting components of these three organisms. Ideally, this will produce an organism that is black because it uses all parts of sunlight. We are using the cyanobacterium Synechocystis as a test laboratory because it is easily accessible for genetic manipulation.
The creation of such a black cyanobacterium would in itself be a breakthrough in the field of photosynthesis enhancement research. Cyanobacteria are important model organisms for biotechnological applications, and such black cyanobacteria could provide the basis for improved production of biofuels and other valuable compounds. Equally important, the results obtained in cyanobacteria can be transferred to the plants that provide our food. To this end, the cyanobacterium can be used as a test laboratory for enhanced photosynthesis, which can then be replicated in its optimised form in plants.
The PhotoRedesign project therefore aims to improve the efficiency of photosynthesis, and more specifically the light reactions of photosynthesis that capture light and convert the captured light energy into molecules that can then be used to convert carbon dioxide from the atmosphere into organic biomolecules. In fact, nature has invented several types of organisms capable of photosynthesis. Because they all go back to a common ancestor, these organisms are still genetically compatible, meaning that their genes also work in the other organisms. We chose three very distantly related organisms that can use very different parts of the sun's light for photosynthesis: cyanobacteria, which are blue-green, plants, which are green, and purple bacteria, which are purple. As mentioned earlier, their different colours indicate that they can use very different parts of the sun's light for photosynthesis.
Our goal is to combine the different light-harvesting components of these three organisms. Ideally, this will produce an organism that is black because it uses all parts of sunlight. We are using the cyanobacterium Synechocystis as a test laboratory because it is easily accessible for genetic manipulation.
The creation of such a black cyanobacterium would in itself be a breakthrough in the field of photosynthesis enhancement research. Cyanobacteria are important model organisms for biotechnological applications, and such black cyanobacteria could provide the basis for improved production of biofuels and other valuable compounds. Equally important, the results obtained in cyanobacteria can be transferred to the plants that provide our food. To this end, the cyanobacterium can be used as a test laboratory for enhanced photosynthesis, which can then be replicated in its optimised form in plants.
Over the four years of the project, we have gained important insights into what is needed to transfer photosystems from plants to the model cyanobacterium Synechocystis. Having a cyanobacterium with plant-like photosystems will be important for testing improved variants of photosynthesis for future use in crops. So far, we have been able to transfer a plant photosystem into Synechocystis and we are now working on bringing this photosystem to full activity. We have also carried out experiments that pave the way for the production of pigments and photosystems from purple bacteria in Synechocystis and have made progress in making these two very different systems compatible. We have also made progress in designing novel antenna systems using artificial intelligence approaches. Finally, we have grown Synechocystis and green algal cells for long periods of time under very intense or fluctuating light to prepare them for the expected effects of enhanced photosynthesis, i.e. more light energy. The cells responded by adapting, i.e. evolving changes in their genes that made them more tolerant to high light without losing much of their performance in low light. These 'hardened' cyanobacteria will be the ideal host for the enhanced photosynthesis we are developing.
Transferring photosystems from plants to prokaryotes and making them functional in this distantly related but still very different environment is very challenging and has never been attempted or achieved before. We expect to further improve the activity of this foreign photosystem during the course of the project. Transferring purple bacterial pigments and photosystems into a cyanobacterium is even more difficult than transferring a plant photosystem into a cyanobacterium, but we have identified preliminary obstacles and are working around them. In terms of creating a chassis to host the enhanced photosynthesis, we have already provided strains that can easily handle much higher energy inputs, so we are well prepared to embed super-efficient photosynthesis into such strains. Although the concept of using evolution in the laboratory has been known for some time in model microorganisms, our experiments are the first of their kind for high light tolerance in a photosynthetic microorganism.