Scientists reveal “beating heart” of photosynthesis

Scientists have solved the structure of one of the key components of photosynthesis, a discovery that could lead to photosynthesis being ‘redesigned' to achieve higher yields and meet urgent food security needs.

The study, led by the University of Sheffield in the United Kingdom, and published in November 2019 in the journal Nature, reveals the structure of cytochrome b₆f – the protein complex that significantly influences plant growth via photosynthesis.

Photosynthesis is the foundation of life on Earth, providing the food, oxygen and energy that sustain the biosphere and human civilisation.

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.

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: “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 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.”

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.

Discovery may result in higher yields of crop plants

Dr Matt Johnson, one of the supervisors of the study, added: “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 nine to ten billion by 2050.”

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.

(University of Sheffield/wi)

Journal reference: 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. Cryo-EM structure of the spinach cytochrome b6 f complex at 3.6 Å resolution. Nature, 2019; DOI: 10.1038/s41586-019-1746-6   
https://www.nature.com/articles/s41586-019-1746-6

More information:
Website of University of Sheffield: https://www.sheffield.ac.uk/news/nr/experts-unlock-photosynthesis-key-help-food-security-1.871479