Natures wonders: when photosynthesis started (Introduction)

by David Turell , Sunday, April 18, 2021, 15:30 (1104 days ago) @ David Turell

Another very early estimate of ability to photosynthesize, possibly at the start of life:

https://www.imperial.ac.uk/news/217553/photosynthesis-could-life-itself/

"Researchers find that the earliest bacteria had the tools to perform a crucial step in photosynthesis, changing how we think life evolved on Earth.

"The finding also challenges expectations for how life might have evolved on other planets. The evolution of photosynthesis that produces oxygen is thought to be the key factor in the eventual emergence of complex life. This was thought to take several billion years to evolve, but if in fact the earliest life could do it, then other planets may have evolved complex life much earlier than previously thought.

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“'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 shows patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve.”

"Photosynthesis, which converts sunlight into energy, can come in two forms: one that produces oxygen, and one that doesn’t. The oxygen-producing form is usually assumed to have evolved later, particularly with the emergence of cyanobacteria, or blue-green algae, around 2.5 billion years ago.

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"The new research finds that enzymes capable of performing the key process in oxygenic photosynthesis – splitting water into hydrogen and oxygen – could actually have been present in some of the earliest bacteria. The earliest evidence for life on Earth is over 3.4 billion years old and some studies have suggested that the earliest life could well be older than 4.0 billion years old.

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"The team made their discovery by tracing the ‘molecular clock’ of key photosynthesis proteins responsible for splitting water. This method estimates the rate of evolution of proteins by looking at the time between known evolutionary moments, such as the emergence of different groups of cyanobacteria or land plants, which carry a version of these proteins today. The calculated rate of evolution is then extended back in time, to see when the proteins first evolved.

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"The photosynthesis proteins showed nearly identical patterns of evolution to the oldest enzymes, stretching far back in time, suggesting they evolved in a similar way.

"First author of the study Thomas Oliver, from the Department of Life Sciences at Imperial, said: “We used a technique called Ancestral Sequence Reconstruction to predict the protein sequences of ancestral photosynthetic proteins.

"'These sequences give us information about 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.'”

Comment: Photosynthesis is so complex we are still picking apart steps we don't understand. As in origin of life it seems obvious design is required since there is no time for a Darwin style evolution caused by a series of random mutations.