Scientists draw single-leaf plant family trees

yellowis one of 85,000 single-leaf plants that now have a clearer family history. Photo Source: Science Website:
although they may look very different, corn and yellow cauliflower have a lot in common. The same is true of tall palm trees and small slippers orchids. Because of a common ancestor 137 million years ago, the roots, seeds, and even leaves of these flowering plants, known as single-leaf plants, look a lot like each other. Now, a new genetic study reveals why: Although all these plants are now "dry ducks," their ancestors lived in water.
Stevens, a taxonomist at the University of Missouri who was not involved in the study, said the work was convincing. "It makes you think about the origin of single-leaf plant features."
scientists have struggled to put single-leaf plants with only one embryonic leaf on the plant evolutionary tree. The evolutionary tree is critical to understanding the evolutionary relationship between the world's 85,000 single-leaf plants. Single-leaf plants include major crops such as corn and rice, grasses eaten by cattle, palm trees, and some of the world's prettiest flowers, such as orchids and lilies.
"In almost every family of single-leaf plants, you can find beautiful and economically and ecologically important members. Elizabeth Kellogg, a plant biologist at the Donald Danfoss Plant Research Center in St. Louis, Missouri, who was not involved in the latest study, said.
Thomas Givnish, an evolutionary biologist at the University of Wisconsin-Madison, knows how important it is to build accurate family trees, especially for crop breeding and basic research. To do this, he pulled together 19 fellow biologists to develop the clearest version of the single leaf plant family tree to date. They sequenced DNA from the leafy bodies of 545 single-leaf plants and 22 other plants. Based on the similarities of these plant DNA, the team clarified their family connections and estimated the age of each branch. "For most of the connections, we have very strong evidence." Givnish said. Among them, their findings include bananas that are closer to ginger and healing plants than previously thought in the branches of the family tree.
really novel is the amount of data they use to solve the whole problem. Stevens said. Most relationships, including bananas and ginger, have been raised before.
, the most striking thing is what's at the bottom of the family tree, says Givnish. The team reported in the American Journal of Botany that the non-single leaf plants most closely associated with this bottom show that the earliest single leaf plants were aquatic. Botanists first came up with this idea in the 19th century, and several researchers explored the origin in the 1990s. But no one has the genetic data that now underpins it. Not only seeds, but the leaves and roots of single-leaf plants are different from among other flowering plants, and aquatic origins may explain why.
, for example, the leaves of single-leaf plants tend to have parallel textures, while the leaves of other flowering plants have branched textures. The latter keeps the leaves as thin as paper hard, otherwise gravity will keep them shaking. But the leaves of the aquatic ancestors of single-leaf plants are presumed to be floating, so they can cope with less developed support systems. At the same time, the leaves of most flowering plants are connected to the stem through the shanks.
the leaf base of single-leaf plants tend to "hook" stems with some "fingers". Like the roots of aquatic plants, the roots of single-leaf plants show fewer branches. At the same time, most single-leaf plants are herbs, not woody. If their aquatic ancestors, like most trees, add annual layers, the newly longer parts will interfere with air catheters that extend from the leaves to the underwater part of the plant.
Stevens says researchers need to compare not just chlorogrete DNA, but more DNA stored in the nucleus. Givnish says the work is already under way. The team analyzed 500 genes from nuclear DNA from multiple species. Their latest findings "largely support the same relationship model" and will be published in
in a few months( Source: Zong hua, China Science
).