The Origin Of The Chloroplast Likely Occurred 2.1 Billion Years Ago


From their humble beginnings in some fresh water environment, there are now hundreds of thousands of species of plants. Quick Shot/Shutterstock

Without them, we as species would not be able to survive. But surprisingly little is known about the origin of plants, particularly when it comes to the initial moment in which the photosynthetic component of plant cells, known as the chloroplast, first originated.

It is well-established fact that the chloroplast that allows plants to harness the energy of the Sun to make food originated when eukaryotes swallowed a type of photosynthesizing bacteria known as cyanobacteria, or blue-green algae. The symbiosis that formed between the two organisms, in which the eukaryote provided protection while the cyanobacteria provided food, is what formed the basis for the evolution of the hundreds of thousands of plants we see today.


But less is known about how this remarkable pairing first came about, when it might have occurred, or to which cyanobacteria the ancestors of the chloroplast is most closely related.

Now a new study, published in the Proceedings of the National Academy of Science, hopes to shed light on the evolutionary history of this pairing that fundamentally changed the direction of life on this planet. The research has shown that the cyanobacteria that was taken up by a eukaryotic cell probably split from its closest ancestor some 2.1 billion years ago.

If the fact that scientists are able to work out the date of such an astonishingly important moment in evolutionary history is not impressive enough, they were able to determine even more about the origins of the organelle. After the initial event, which amazingly is only thought to have occurred once, it then took a further 200 million years for the symbiotic relationship between the two organisms to cement itself.

Not only that, but the researchers were also able to use ancestral trait reconstructions to determine that rather than happening in the oceans over 2 billion years ago, it probably occurred in a freshwater environment. Marine algae evolution then occurred much later on, taking another 1.3 billion years to diversify. These impressive findings could change how we think about major ecological functions.


“The results of this study imply that complex organisms such as algae first evolved in freshwater environments, and later colonized marine environments," explained Dr Patricia Sanchez-Baracaldo, who co-authored the study, in a statement. "[T]hese results also have huge implications for understanding the carbon cycle,”

They hope that this latest research can help to build up a much more detailed and accurate picture of what the world looked like before the evolution of plants, and at a critical point in the history of our planet.

  • tag
  • evolution,

  • algae,

  • photosynthesis,

  • plants,

  • cyanobacteria,

  • eukaryotes,

  • chloroplast