About three billion years ago, mono -cells have ruled Earth. Then, about a billion years ago, a new chapter of life began. Early attempts to live the team began to stick, and pave the way for the development of complex organisms, including animals, plants and fungi.
In all known life, the transition to multi -cell occurred at least 40 times.1. However, in animals, it appears to have happened only once.
Starting from the early first decade of the twentieth century, researchers interested in this wonderful event made a series of unexpected discoveries. The prevailing opinion saw that a flood of genes should have evolved to enable the main characteristics of multiple cells2The ability of cells to stick to each other, contact the molecular signals and coordinated organization of the genetic expression that causes each specialized cell and take its position in the organism. But studies have found that some mono -cell organisms express a large number of proteins that control the properties of pluralism in animals3and4. It seems that the collection of molecular tools required for rear pluralism was present long before the appearance of the first animals.
“This work rewrites our understanding of animal origins,” says William Ratcliffe, an evolutionary biologist at the Georgia Institute of Technology in Atlanta. “This makes us ask different questions.”
The two teams have led many of this research, the world of evolutionary biology and genetic scientist Nicole King at the University of California, Berkeley, and the evolutionary biologist Ihaki Ruiz Trilio at the Evolutionary Biology Institute in Barcelona, Spain. They have since expanded a small community of scientists who have developed more than dozens of these species to model beings. All of these species are the real nucleus, which differs from the mediator of the core in that it has a nucleus, and belongs to the genealogy is closely related to animals: Choanoflagellates, Filasteans, Ichthyosporeans and Coralochytreans (see “monochrome animal relatives). Many typical species flow into pluralism through the formation of Colonies from time to time.
source: Ruiz-Trillo, I. And others. year. Reverend microbol. 77499-516 (2023).
Part of what makes these extremely interesting organisms is how different they are-in appearance, the stages of life and genetic makeup-the researchers say. Each of the organisms, five of which here, provides a peek at the evolutionary paths that can lead to animals. Looking at many genealogies to collect this event has become “the philosophy of this scientific community,” says molecular biologist Elena Kasakoberta, who runs the laboratory in Barcelona with Ruiz Trillo. “Only with a comparative approach we can try to get a more accurate picture.”
The upper model
When Chanovlagilat is one cell Salpingcaa rosetta She is divided into the presence of bacteria, her daughter’s cells form a pink pattern.Credit: Mark Dayel
Salpingcaa rosetta Among the living organisms that King achieved in her early work on the multiplicity of Zilani. It belongs to Choanoflagelles, which is the closest relative of the animal. This group has diverged from a common ancestor with animals more than 600 million years ago.
Such as other Choanoflagellates, Q. Rosita It contains the body of spherical cells that includes a collar of fine membrane protrusions called microvilli, which is used to capture bacteria that are swept for dinner with a long tail (known as a whip). It was isolated in 2000 from the clay surfaces off the coast of Virginia; Researchers were unable to find it again in the wild. Under certain environmental conditions, Q. Rosita The cells are divided up in the form of a clion, resulting in the cells of a genetically identical daughter that form colonies by rotating in a pink style, with a wavy whip abroad. But when King began working with the organism in the laboratory for the first time, it could not falsify it from its mono -cell shape. The experience experience revealed that the secretions preceded by a specific prey bacteria act as a sign of cells to start division.
A “lost world” of early microbes flourished a billion years ago
In addition to the formation of roses, the organism has at least one multi -cell formation and some distinct free living cells. When limited to a narrow space, for example, Q. Rosita The cells withdraw their whip and become the Amalwi, lack a fixed shape and extend thin claws called filopodia to pull themselves.
“It has an amazing diversity in response to countless environmental sermon,” says David Booth, the University of California’s biochemistry, San Francisco.
In 2003, King and her colleagues reported the presence of proteins involved in adhesion cells and cell signs in Chanovlaglat types3. Later, identify a more deeper tool set for cell connectivity when the genome sequence Q. Rosita5.
Salpingcaa rosetta he Fruit From Choanoflagellates – the most widely studied species and the species that researchers developed the most comprehensive tools to change the genome directly. In 2018, during the post -PhD stage at the King’s Laborat Q. Rosita6 In 2020, I found ways to liberate her genome using CRISPR7. These methods have made it possible to tamper with genes that researchers say can be the key to pluralism – and the study of proteins expressed by these genes.
With the help of the tools, the world of microorganism, Ariel Woznika at the University of Texas at Austin, a former high school student at King’s Laboratory, explores how Chanovlagils respond to bacterial attackers. The biochemical Florentin Rotaganera, which is the previous doctorate at the King’s laboratory now at Stanford University in California, is achieving in enzymes called Kinaz Trechpins from the cell signals in animals in similar numbers in Q. Rosita.
Magdide
Environmental signals can lead to assembly in Capsaspora Shepdogs.Credit: H. Suga And others./Common nature.
Capsaspora Shepdogs He is a member of the FilaSterean dynasty, which has diverged from a common ancestor with animals, perhaps a few hundred million years ago than Choanoflagellates.
Ruiz-Trillo first became interested in the organism like a mail, just as the King’s Stupt Laboratory was to study Q. Rosita. He and his colleagues found that C. ShepherdAlso, it seems closely related to animals4. Ruiz-Trillo has begun to study genealogy other than Choanoflagelles, because the investigation of many genealogy can provide a complete picture of common grandfather with animals. After the Genome sequence C. ShepherdRuiz Trillo and his team in 2013 said that it contains many genes related to multiple cells, including some that Chanovlagilat-like those that cod the surface proteins of cells called Integrins, which helps cells to stick to their environment and environment8.
These strange ancient species rewrite animal development
In 2002, discovered in fresh water snail, C. Shepherd Most of her life cycle spends a single -cell amoiba, but environmental signals can push cells to a multi -cell stage where groups collect together and integrate to grow in largely large groups. This path to multi -cell is different from assembly through the shells that was observed in Choanoflagellates. Ruiz-Trillo says that the clonal division is “the usual way that people were thinking about the development of animals.”
During the development of animals, one cell is divided into many identical cells, a process that may avoid any genetic conflict arising between cells. Therefore, it is easy to assume that the shelling was also the evolutionary path of the first animals, says Ruiz Trillo. But the assembly is present in many real -core genealogies as a quick and easy cell to form 3D structures, and it is believed that this mechanism deserves a closer look.
Ruiz Trillo and his colleagues found it C. Shepherd It uses some main genes related to multiple cells during this combined stage9. Perhaps the assembly was the basic step in the development of animals, says Ruiz Trillo, or perhaps it was one part of the process.
Capsaspora Shepdogs It is one of a handful of mono-cell species sent by Casacuberta and Ruiz-Trillo happily to other laboratories upon request.
Duo
In the water from the tidal gathering, a colony from Choanoeca Flexa The cells taken in the form of a seat reflect their curvature. Another colony that joins it, and reflects its curve again.Credit: Benjamin T. Larson
Specific discovery in 2017 for other types of Chanovlagils, Choanoeca FlexaIt has proven the amount of contrast in this group alone. Thibaut Brunt, a biologist now, found evolutionary cells at the Pasteur Institute in Paris, C. Flexa In Korasaw, with his colleagues while he was attending a Kinda workshop at King’s Laboratory. After collecting water samples from the shallow marine tidal baths as he toured the island, he and his colleagues pressed the scene of the accident under the microscope.
Individual cells, which look like Q. Rosita Cells, make a single -layer sheet of cabin, with each whip indicate the same direction10. In response to light or darkness, “they can reverse their curvature in a few seconds, and they turn from the inside to the outside like a child or umbrella game,” says Bronette. “We were screaming and jumping up and down when we saw it – we may have been ridiculous.”
The secret life of the cells – as it has never been just before
Although researchers are still developing ways to treat his genome, C. Flexa It has at least one great benefit as a living object. Evolutionary biologist Nuria Rose Rotcher, post -PhD at Brunett Laboratory, says that other living organisms have only been studied in the laboratory after their discovery. Researchers do not know how or where they can be found again. but C. Flexa It was repeatedly retrieved from the tidal pools that were found for the first time. “We were very fortunate, because we can return to the natural environment to understand how it is linked to the behavior of the multi-cell being,” says Ros-Rocher.
These ponds face the changes in the injury – the water often heats and evaporates within days, leaving the organism on its feet in a sharp or beach salinity on the dried mud before the tide is flooded again. Brunett and his team found it C. FlexaHe loves Q. RositaIt can be transmitted from the condition of mono -cell to multiple cells by the linguistic division. But the assembly can also be used, and sometimes it combines both strategies at the same time.