The study, led by the University of Sheffield and published today in the journal Nature, reveals the structure of cytochrome b6f -- the protein complex that significantly influences plant growth via photosynthesis.
Using a high-resolution structural model, the team found that the protein complex provides the electrical connection between the two light-powered chlorophyll-proteins (Photosystems I and II) found in the plant cell chloroplast that convert sunlight into chemical energy.
"Our study provides important new insights into how cytochrome b6f utilises the electrical current passing through it to power up a 'proton battery'. This stored energy can then be then used to make ATP, the energy currency of living cells. Ultimately this reaction provides the energy that plants need to turn carbon dioxide into the carbohydrates and biomass that sustain the global food chain,” Lorna Malone, the first author of the study and a PhD student in the University of Sheffield's Department of Molecular Biology and Biotechnology, said.
The high-resolution structural model, determined using single-particle cryo-electron microscopy, reveals new details of the additional role of cytochrome b6f as a sensor to tune photosynthetic efficiency in response to ever-changing environmental conditions. This response mechanism protects the plant from damage during exposure to harsh conditions such as drought or excess light.
The ’beating heart’ of photosynthesis for ‘bigger and better’ plants
Dr Matt Johnson, reader in Biochemistry at the University of Sheffield and one of the supervisors of the study, explained: "Cytochrome b6f is the beating heart of photosynthesis which plays a crucial role in regulating photosynthetic efficiency.
"Previous studies have shown that by manipulating the levels of this complex we can grow bigger and better plants. With the new insights we have obtained from our structure we can hope to rationally redesign photosynthesis in crop plants to achieve the higher yields we urgently need to sustain a projected global population of 9-10 billion by 2050."
Dr Johnson stressed that the need to produce enough food for this number of people will require the sector to look to methods including genetic engineering to improve the efficiency of food production. “The dramatic increase in food production required by our growing population means we aren’t going to be able to wait around for evolution to [make photosynthesis more efficient] for us. That is why approaches like genetic engineering are so important for improving crops.”
The research was conducted in collaboration with the Astbury Centre for Structural Molecular Biology at the University of Leeds.
Researchers now aim to establish how cytochrome b6f is controlled by a myriad of regulatory proteins and how these regulators affect the function of this complex.
Cryo-EM structure of the spinach cytochrome b6 f complex at 3.6 Å resolution
Authors: Lorna A. Malone, Pu Qian, Guy E. Mayneord, Andrew Hitchcock, David A. Farmer, Rebecca F. Thompson, David J. K. Swainsbury, Neil A. Ranson, C. Neil Hunter, Matthew P. Johnson
Additional materials provided by the University of Sheffield