As the old saying goes, a flower does not become thornless. But according to botanists, roses do not have thorns. The pointed ridges on the rose stem are called “blades” and are biologically distinct from the stiff, woody spines of other plants.
Razors are an example of convergent evolution. This phenomenon occurs when unrelated species exhibit similar traits due to similar environments. In the past 400 million years, plants have evolved blades 28 different times. The blade grows on the stems of roses, while in other plants it appears on their leaves or fruits.
The blade pattern is different in plants. In grasses (dark wheat), tiny blades grow on their stigma. Solanum atroporpureum (Solanum atropurpureum), a wild relative of the potato that grows in Brazil, has blades so nasty that it’s earned the nicknames “purple devil” and “evil.”
Photographer: Adrian Davies / Alamy
A new study published in the journal Science reveals how plants evolved blades several times from scratch. Each species used the same gene over and over again to make a blade. This discovery makes it possible to change the DNA of plants to remove their blades and make it easier to grow some wild plants as agricultural crops.
Zakaria Lipmana plant geneticist at the Cold Spring Harbor Laboratory, became curious about blades while studying a group of crops including potatoes, tomatoes, and eggplants. Although none of these products have blades, some of their wild relatives are covered in small daggers. Probably the first farmers, when they used these plants as agricultural products, were able to remove the blades from them by controlled breeding. They deliberately chose plants that were bladeless or had fewer blades. Over generations, this process led to the gradual reduction or elimination of blades.
“Who wants to grow eggplants that constantly have razor blades when you eat them,” says Lipman. [در پوست شما] sink in?”
The first farmers removed the blade from crops by selecting bladeless plants for subsequent crops
The removal of the razor blades led Dr. Lipman and his colleagues to wonder how razor blades evolved in the first place. Blades probably evolved as a defense mechanism against herbivores. When animals try to ingest these plants, the blades act as a deterrent. However, they also have other functions
Some plants use blades to hook themselves to surfaces, which help them climb up and reach sunlight. Wild grasses also use blades to attach their seeds to the fur of passing animals, facilitating seed dispersal. In general, blades have multifaceted roles in plant survival and adaptation to the environment.
Charles Darwin recognized that some traits can evolve independently multiple times in the history of life in a process known as “convergent evolution”. For example, bats and birds evolved wings for flight; But they chose different evolutionary paths to reach the same destination. Bat wings evolved as membranes growing between their toes, while birds evolved wings from feathers.
To understand how plants convergently evolved blades, Dr. Lipman and his colleagues crossed a species of domestic eggplant with its wild blade-bearing relative. Some hybrids had many blades, while others had none.
By comparing the plants’ DNA, the scientists discovered that a special type of gene called LOG is carried only by plants with blades. Botanists have long known that LOG genes help produce a hormone that signals plant cells to grow. However, in wild eggplant, a special version of the LOG gene allows the growth of spines.
Dr. Lippmann conducted a similar experiment on two other types of eggplant and crossed them with their wild relatives. At each turn of the experiment, the researchers discovered that a variant of the LOG gene was responsible for making blades in wild plants.
“We found that,” Dr. Lipman said [این] It is the same gene that independently has mutations in all three lineages [بادمجان] brought together to destroy these blades”; This means that in three lineages (groups of related species), the same gene has undergone an independent mutation. These mutations led to the loss of the blades of those plants. Despite the different evolutionary paths of this lineage, a common genetic change led to the absence of blades.
It may seem puzzling that the LOG gene mutation can remove blades without damaging the entire eggplant. However, LOG genes are essential for plant growth.
Although the LOG gene is essential for plant growth, its deletion does not harm the entire plant
Scientists have discovered that plants have evolved many copies of LOG genes, each with specific roles, over millions of years. Dr. Lipman and his colleagues suspect that a specific version of the LOG gene may have evolved in the wild ancestor of eggplants to produce blades; While other versions of this gene continued to perform their essential function to help the overall growth of the plant.
LOG genes play an important role in the formation of blades in different plant species. Dr. Lipman and his colleagues found evidence of this connection in several other plants. For example, when they blocked the LOG gene in roses, it disrupted blade growth. They observed that these large blades could be significantly reduced to small protrusions.
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Dr Lipman said the new findings could help scientists turn wild plants into crops. He and his colleagues tested this possibility on a wild Australian plant called desert raisin. This sweet fruit usually has a blade; But after researchers isolated the LOG gene from its DNA, it became razor-less.
Vivian Irishan evolutionary biologist at Yale University who was not involved in the new study, said it shows that convergence can happen in a way that Darwin didn’t expect. Each time blades evolved, plants didn’t invent an entirely new way to make them. Instead, they just borrowed the same gene over and over again.
“Innovation in many cases may simply reflect the re-use of old genes in new ways,” Dr Irish said.
