Researchers have found that early life on Earth could perform crucial steps in Oxygenic Photosynthesis. This significantly changes our view of the evolution of life on Earth.
It was previously thought that the evolution of photosynthesis that produces oxygen is a key factor in the emergence of complex life. It was thought that this took billions of years to evolve. But if early life on Earth could perform photosynthesis, then this could mean that other planets may have evolved complex life earlier than previously believed. Hence this study also changes how we viewed the evolution of life on other planets.
The research was conducted by scientists from Imperial College London. They traced the evolution of proteins that are required for photosynthesis back to the origin of bacterial life on Earth.
Lead researcher Dr Tanai Cardona, from the Department of Life Sciences at Imperial, said, “We had previously shown that the biological system for performing oxygen-production, known as Photosystem II, was extremely old, but until now we hadn’t been able to place it on the timeline of life’s history. Now, we know that Photosystem II show patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve.”
Evolution of Oxygenic Photosynthesis
Photosynthesis is of two forms – one that produces oxygen and one that does not. Oxygenic photosynthesis was believed to have come around with the emergence of cyanobacteria, or blue-green algae, around 2.5 billion years ago. Even though research showed that traces of oxygenic photosynthesis was found before this, it was still considered to have taken billions of years to evolve.
According to the new research, enzymes that are able to perform the key process in oxygenic photosynthesis, that is splitting water into hydrogen and oxygen, were present in early bacteria. It can be expected that the early version of oxygenic photosynthesis was very simple and inefficient.
It took bacteria more than a billion years to perfect this process which led to the emergence of cyanobacteria. It took two billion years more for plants and animal life to develop on Earth. The fact that oxygen production was present this early suggests that in other planets, complex life could have developed in a much lesser time.
The first author of the study Thomas Oliver, from the Department of Life Sciences at Imperial, said, “We have used a technique called Ancestral Sequence Reconstruction to predict the protein sequences of ancestral photosynthetic proteins. These sequences give us information on how the ancestral Photosystem II would have worked and we were able to show that many of the key components required for oxygen evolution in Photosystem II can be traced to the earliest stages in the evolution of the enzyme.”
Insights into the evolution of oxygenic photosynthesis protein are important while understanding life on other planets. It can also help scientists use photosynthesis in innovative ways through synthetic biology.
Dr Cardona, who is leading such a project as part of his UKRI Future Leaders Fellowship, said, “Now we have a good sense of how photosynthesis proteins evolve, adapting to a changing world, we can use ‘directed evolution’ to learn how to change them to produce new kinds of chemistry. We could develop photosystems that could carry out complex new green and sustainable chemical reactions entirely powered by light.”