Taylor Nicioli
Other than being a symbol for love and romance, roses are commonly known for their sharp spikes — prickles that protrude from the stems to ward off animals looking to munch on the buds.
They’re not the only plant to have this defense mechanism: Other flowers such as spider flowers or brambles, the flowering shrub responsible for raspberries and blackberries, bear the sharp points, as do certain crop plants such as tomatoes, eggplants, barley and rice.
But how could all these species, many of which evolved separately over the course of millions of years, come to have the same spiny feature? A team of international researchers found that the answer lies in their DNA, tracing the origin to one ancient gene family that’s responsible for the prickles in all these variations, according to a new study published Thursday in the journal Science.
The findings not only open the door for scientists looking to create prickle-free variants but also provide insight into the evolutionary history of an extremely diverse genus of plants, experts say.
The evolution of prickles
Contrary to pop culture references, roses do not have thorns, which are the sharp woody points of certain shrubs and trees, including honey locusts and citrus trees. The flowers instead have prickles that form from the skin of the plant, similar to how hair grows.
Prickles have been around for at least 400 million years, dating back to when ferns and their relatives emerged with some bearing prickles on their stems. The trait has since then popped up — and disappeared — at different points in evolutionary time, said study coauthor Zachary Lippman, plant biologist and professor of genetics at Cold Spring Harbor Laboratory on Long Island, New York.
One of the most diverse plant genera, known as Solanum — which includes crops such as potatoes, tomatoes and eggplants — first gained prickles 6 million years ago. Today, the genus has more than 1,000 species that appear throughout the world, with around 400 of those referred to as “spiny solanum” for their prickles, according to the University of Utah.
When a common trait, such as prickles, appears independently across different lineages and species, that is known as convergent evolution, and occurs when species adapt similarly to certain environmental needs. Wings are another example of a feature that evolved in this way among different species of birds, as well as other animals such as bats and even some types of squirrels that have the winglike structure, said Lippman, who is also a Howard Hughes Medical Institute investigator.
Prickles and thorns are an evolved defense against herbivores — animals that eat plants — and can also aid in growth, plant competition and water retention, according to the study. It was previously unknown as to what exactly caused ferns and other unrelated plants to grow the prickles. Now, the study authors have found that an ancient gene family known as Lonely Guy, or LOG, has served as a gatekeeper for the trait, switching it on and off in different species across millions of years.
