Scientists uncover secret of how algae turned world green

One of Nature's greatest secrets, how ocean slime turned the world green with vegetation, has been uncovered by scientists.

Ancient algae were already genetically programmed to survive out of water before colonising the land and evolving into the plants that transformed life on Earth, experts discovered.

The big change 450 million years ago dramatically altered the global climate and set the stage for the story of terrestrial evolution that ultimately led to the human race.

Scientists already knew that plant life was only able to take root on the land by forming symbiotic relationships with beneficial microscopic fungi.

But just how the algae survived long enough on dry land to evolve the close microbiotic partnership has been a deep mystery.

The answer appears to be that they already possessed the genetic programming necessary for the transition before they even left the water.

Dr Pierre-Marc Delaux, from the John Innes Centre in Norwich, said: "At some point 450 million years ago, algae from the Earth's waters splashed up on to barren land.

"Somehow it survived and took root, a watershed moment that kick-started the evolution of life on earth. Our discovery shows for the first time that the algae already knew how to survive on land while it was still in the water. Without the development of this pre-adapted capability in algae, the earth could be a very different place today.

"This finding has filled a gap in our collective knowledge about the origins of life on earth."

The research is reported in the journal Proceedings of the National Academy of Sciences.

Working with colleagues from the US, the John Innes team found that the aquatic algae from which all terrestrial plant life arose were pre-adapted to recruit fungi to help them to acquire nutrients from the soil.

Many modern plant species depend on similar symbiotic relationships with micro-organisms to survive.

Legumes, the class of vegetables that includes beans, peas and lentils, depend on nitrogen-fixing bacteria, for instance. Many other plant species rely on relationships with fungi to convert soil minerals into bioaccessible forms.