Researchers have shed new light on how plant life originated on Earth
Researchers from the University of Copenhagen have shed new light on how plant life originated on our planet. Specifically, they showed that two genes are necessary for terrestrial plants to protect themselves from attack by fungi – a defense mechanism that dates back 470 million years. It is likely that these defenses paved the way for all terrestrial plant life.
Plants evolved from aquatic algae to the ability to survive on Earth nearly half a billion years ago, laying the foundation for life on Earth. One of the obstacles that made this dramatic transformation so difficult was the fungi:
It is estimated that 100 million years ago, fungi crept across the Earth’s surface in search of food, most likely found in dead algae washed up from the sea. So, if you, as a new plant, are going to establish yourself on the ground, and the first thing you encounter is a fungus that eats you, you need some kind of defense mechanism,” says Mads Eggert Nielsen, a biologist in the Department of Plant and Environmental Sciences 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 narrowed down to two genes, PEN1 and SYP122. Together, they help form a type of component in plants that prevents the invasion of fungi and fungi-like organisms.
“We discovered that if we destroy these two genes in our model of Arabidopsis, we open the door for pathogenic fungi to penetrate. We have found that they are essential for the formation of this cell wall-like plug that protects against fungi. Interestingly, it appears to be a universal defense mechanism found in all terrestrial plants,” says Mads Eggert Nielsen, senior author of the study, which was published in the journal Science. eLife.
I grew up in 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 inserting them into cressus, the researchers examined whether they could determine the same effect. The answer was yes.
“Although the two plant families to which Arabidopsis and liverwort belonged evolved in divergent directions 450 million years ago, they continued to share genetic functions. We believe that this family of genes arose with the unique purpose of managing this defense mechanism, and thus it was one of the foundations for plants to establish themselves on Earth,” says Mads Eggert Nielsen.
The coexistence of plants and fungi
While fungi were an obstacle to plants in their transition from marine algae to becoming terrestrial plants – they were also a prerequisite. Mads Eggert Nielsen explains that once plants were able to survive the attacks of the fungi seeking to eat them on Earth, the next problem they faced was finding the nutrients:
Plants in aquatic environments have easy access to dissolved nutrients such as phosphorous and nitrogen. But 500 million years ago, the soil as we know it today didn’t exist — just rocks. Nutrients bound to the rocks are extremely difficult for plants to obtain. But not for fungi. On the other hand, fungi cannot produce carbohydrates – which is why they consume plants. This is where the symbiotic relationship between plants and fungi is thought to have arisen, which then became the basis for the explosion of terrestrial plant life during this period.”
The defensive structures that form in the plant do not kill the plant or the fungus, they simply prevent the fungus from invading.
“Because the fungus can only gain partial entry into the plant, we think the tipping point arises where both the plant and the fungus have something to gain. Therefore, it was beneficial to keep the relationship as is. The theory that plants tame fungi to colonize the land is not ours, but we provide forage that supports this idea,” says Mads Eggert Nielsen.
Can be applied in agriculture
The new findings 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 attacks, which is a big problem for farmers.
“If all plants defend themselves in the same way, this should mean that microorganisms capable of causing diseases – such as powdery mildew, yellow rust and potato rot – have found a way to infiltrate, stop or evade their respective host plants’ defenses. We want to know how they do it. We will then try to transfer the defensive components from the resistant plants to those plants that get disease, thus achieving resistance,” says Mads Eggert Nielsen.
Mads Eggert Nielsen is participating in a research project in the Department of Botanical and Environmental Sciences led by Hans Thordal-Christensen and supported by the Novo Nordisk Foundation that focuses on making crops more resistant by identifying defense mechanisms in plants that disease-causing microorganisms are trying to address. close.
Researchers have long assumed that the PEN1 and SYP122 genes performed a special function regarding the transition of plants from their aquatic phase as algae to terrestrial plants, but there has been no concrete evidence as to whether they are indeed a prerequisite for plants. defensive capabilities.
Previous studies have shown that by destroying the PEN1 gene, plants lose their ability to defend themselves against powdery mildew. However, 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, 4 Feb 2022, Available here. eLife.
DOI: 10.7554 / eLife.73487