Scientists have shed new light on how plant life originated on Earth
researchers from the University of Copenhagen It has shed new light on how plant life originated on the surface of our planet. Specifically, they showed that two genes are necessary for land plants to protect themselves against fungal attack – a defense mechanism that goes back 470 million years. It is likely that these defenses paved the way for all plants on earth.
Plants evolved from aquatic algae to the ability to survive on Earth nearly half a billion years ago and laid the foundation for life on Earth. One of the obstacles that made this dramatic transformation so difficult was the fungi:
An estimated 100 million years ago, fungi crawled across the earth’s surface in search of food, probably found in dead algae washed up from the sea. So if you have to establish yourself as a new plant on earth, and the first thing you come across is a fungus that eats you, you need some kind of defense mechanism, “says Mads Eggert Nielsen, biologist at the Department of Plant Health. and Plant Science. Environmental Science at the University of Copenhagen.
According to Mads Eggert Nielsen and research colleagues from the Department of Plant and Environmental Sciences and the University of Paris-Sclay, the core of this defense mechanism can be reduced to two genes, PEN1 and SYP122. Together, they help to form a type of component in plants that prevents the invasion of fungi and fungus-like organisms.
“We found that if we destroy these two genes in our model of Arabidopsis, we open the door for pathogenic fungi to enter. We found that they are essential for the formation of this cell wall-like plug that “Interestingly enough, it seems to be a universal defense mechanism found in all land plants,” said Mads Eggert Nielsen, senior author of the study, which was published in the journal Science. eLife†
I grew up on a 470 million year old factory
The research team tested the same function in the liverwort, a direct descendant of one of the first land plants on Earth. By taking the two matching genes in the liverwort and placing them in cressus, the researchers investigated whether they could determine the same effect. The answer was yes.
“Although the two plant families to which Arabidopsis and liverwort belonged evolved in different directions 450 million years ago, they continued to share genetic functions. We believe that this family of genes has arisen with the unique purpose of controlling this defense mechanism, and it was therefore one of the foundations for plants to establish themselves on the ground, says Mads Eggert Nielsen.
The coexistence of plants and fungi
While fungi were an obstacle for plants in their transition from marine algae to land plants, they were also a requirement. Mads Eggert Nielsen explains that once plants could survive the attack of the fungi they would eat on Earth, the next problem they faced was finding nutrients:
Plants in aquatic environments have easy access to dissolved nutrients such as phosphorus and nitrogen. But 500 million years ago, the earth as we know it today did not exist – only rocks. Nutrients bound to the rocks are extremely difficult for plants to obtain. But not for mushrooms. On the other hand, fungi cannot produce carbohydrates – that is why they consume plants. This is where the symbiotic relationship between plants and fungi is said to have developed, which subsequently became the basis for the explosion of terrestrial plant life during this period. ”
The defensive structures that form inside the plant do not kill the plant or the fungus, they simply prevent the fungus from penetrating.
“Because fungi can only partially penetrate the plant, we think there is a turning point where both the plant and the fungus have something to gain. Therefore, it was a help to keep the relationship as it is. The theory that plants tame fungi to colonize the soil Not ours, but we provide feed that supports this idea, ”says Mads Eggert Nielsen.
Can be used in agriculture
The new results add an important piece to the puzzle of the evolutionary history of plants. More importantly, they can be used to make crops more resistant to fungal attack, which is a major problem for farmers.
“If all plants defend themselves in the same way, it should mean that microorganisms that can cause disease – such as powdery mildew, yellow rust and potato rot – have found a way to infiltrate, stop or suppress the defenses of their respective host plants. dodge. We want to know. How do they do it. We will then try to transfer the defense components from the resistant plants to those who get the disease, and thus achieve resistance, ”says Mads Eggert Nielsen.
Mads Eggert Nielsen participates in a research project at the Department of Botanical and Environmental Sciences led by Hans Thordal-Christensen and supported by the Novo Nordisk Foundation, which focuses on making crops more resistant by identifying defense mechanisms in plants that contain disease-causing microorganisms. try to tackle. close.
Researchers have long believed that the genes PEN1 and SYP122 served a special function in the transition of plants from their water phase as algae to terrestrial plants, but there is no concrete evidence that they are actually a requirement for plants. defensive abilities.
Previous studies have shown that by destroying the PEN1 gene, plants lose their ability to defend themselves against powdery mildew. But when the closely related gene, SYP122, is destroyed, nothing happens. The new research results show that the two genes together constitute an important key in the plant’s defense mechanism.
Reference: “Plant SYP12 Structures Mediate an Evolutionarily Conserved General Immunity to Nematode Pathogens” by Hector M Rubiato, Mingqi Liu, Richard J O’Connell and Mads E. Nielsen, available February 4, 2022. eLife.
DOI: 10.7554 / eLife.73487