Researchers shed new light on how plant life became established on the surface of the Earth
Researchers from the University of Copenhagen have shed new light on how plant life got established on the surface of our planet. They specifically demonstrated that two genes are crucial for terrestrial plants to protect themselves against fungal attack – a defense mechanism that dates back 470 million years. These defenses most likely paved the way for all terrestrial plant life.
Plants evolved from aquatic algae to being able to survive on land roughly half a billion years ago, laying the groundwork for life on land. Fungi were one of the obstacles that made this dramatic transition so difficult:
“It is estimated that 100 million years prior, fungi crept across Earth’s surface in search of nourishment and most likely found it in dead algae washed up from the sea. So, if you, as a new plant, were going to establish yourself on land, and the first thing you encountered is a fungus that would eat you, you needed some sort of defense mechanism,” says Mads Eggert Nielsen, a biologist at the University of Copenhagen’s Department of Plant and Environmental Sciences.
According to Mads Eggert Nielsen and his research colleagues from the Department of Plant and Environmental Sciences and the University of Paris-Saclay, the essence of this defense mechanism can be narrowed down to two genes, PEN1 and SYP122. Together, they help form a kind of plug in plants that blocks the invasion of fungi and fungus-like organisms.
“We found out that if we destroy these two genes in our model plant thale cress (Arabidopsis), we open the door for pathogenic fungi to penetrate. We found that they are essential to form this cell wall-like plug that defends against fungi. Interestingly, it appears to be a universal defense mechanism that is found in all terrestrial plants,” says Mads Eggert Nielsen, senior author of the study, which is published in the journal eLife.
Originated in a 470-million-year-old plant
The research team has tested the same function in liverwort, a direct descendant of one of Earth’s very first land plants. By taking the two corresponding genes in liverwort and inserting them into thale cress, the researchers examined whether they could identify the same effect. The answer was yes.
“Even though the two plant families that Arabidopsis and liverwort belong to evolved in divergent directions 450 million years ago, they continue to share genetic functions. We believe that this gene family emerged with the unique purpose of managing this defense mechanism and has thus been one of the foundations for plants to establish themselves on land,” says Mads Eggert Nielsen.
A symbiosis between plants and fungi
While fungi posed an obstacle for plants in their transition from an algal marine stage to becoming land plants – they were also a prerequisite. As soon as plants could survive attacks from fungi…