In science, the theory is popular that the first life on Earth appeared in the so-called "primary broth". The carbon-based elements in this broth were connected to each other in simple molecules, until eventually they initiated the birth of a primitive life. But a further step in evolution causes a lot of disputes and discussions among scientists.
According to one popular hypothesis, ribonucleic acid (RNA) molecules, containing the genetic code of proteins and capable of performing the functions of simple chemical reactions, were what initiated the life on our planet. Some scientists reject this idea and say that RNA is too large and complex structure in order to have the right to wear the title of a catalyst for life. According to these scientists, even before the appearance of macromolecules in the form of RNA, simpler molecules were able to develop the ability to use metabolic functions, without which no RNA would exist. In general, this idea stands for the fact that at the head of everything, that is, the very first appeared exactly the metabolism. And the new evidence of the scientific group from the University of Illinois only reinforces this idea.
"All living beings have a metabolism, a set of vital chemical transformations that allow these organisms to provide energy and matter for the functioning of cells. These metabolic transformations most likely appeared on Earth very early. It is possible that the first organisms borrowed the chemical reactions already available at that time on the planet, having assimilated them into cells through the development of enzymatic activity, "says Gustavo Caetano-Anolies, bioinformatics and professor of the plant cultivation department at the University of Illinois.
Cayetano-Anolies and his colleague Ibrahim Koch from the Turkish Gebze Technical University decided to test the theory of "metabolic primacy" through an analysis of the molecular functions of organisms present in all the kingdoms and studied the genome (set of genes) of 249 individual organisms whose information is presented in the project database « ". This database is unique because it contains not only information about each product of genes - proteins or RNA molecules, but also a description of the functions of each individual gene of these organisms.
"You can take the whole genome represented in the body, for example, human, and visualize it through a set of functional characteristics of each individual gene. The study of these "functions" can tell you about what exactly this or that gene is doing. For example, we can find out which type of catalytic, recognition or binding functions a specific gene product has, which is much more intuitive for research, "comments Cayetano-Anolles.
"The best way to understand a living organism is to find out the functions of its genes," the scientist continues.
From the words of Cayetano-Anolies, the presence of the same function in the genome in different species can speak of the evolutionary importance of this function. Thus, the researchers studied all the molecular functions of the disassembled organisms, counted them, and derived those that were encountered in all cases. The main idea behind all this is that the very first, that is, the most basic functions, such as the catalytic processes responsible for the appearance of metabolism, most likely were endowed with all the organisms of that time and, therefore, will be found all along the so-called tree of life. At the same time, those functions of genes that appeared later than all others, on the contrary, will occur in a smaller number of species of living organisms.
With the help of modern information and computer methods, researchers created a tree that depicts the paths leading to the most basic molecular functions. Closer to the base of this tree (that is, closer to the roots) are the most ancient functions. More "fresh" functions, in turn, are closer to its top.
It turned out that only two molecular functions can be distinguished at the very basis of this tree, which, most likely, laid the foundation for life on Earth. It is metabolism and molecular bonds.
"It is entirely logical to assume that these two functions were the first to appear. Since molecules needed energy to produce metabolism. In addition, they needed to interact with each other, "explains Cayetano-Anolies.
Next appeared functions that made possible the appearance of macromolecules. It was here that RNA might have appeared. Next came the mechanisms that allowed the molecules to integrate into the cells, and then the functions that allowed the cells to interact with each other and their environment.
"In the end, getting to the tree crown, we see functions related to complex processes involving the production of muscles, skin or the nervous system," says Caetano-Anolies.
By their research, scientists do not just shed light on the past of life. Recall that evolution continues to this day. Therefore, understanding the sequence of the formation of these molecular functions through time can help us predict where life on earth will move further.
"When people talk about evolution, they look back. We would like to develop chronological and methodological models that could answer the question of where evolution is going and what new molecular functions we should expect from it in the future, "Cayetano-Anolies comments.
The work of today's specialists will definitely be able to find its application in bioengineering, the growing sphere of the use of biological information and computer calculations for the creation of new biological forms. According to Caetano-Anolas, the development of new genes in the future will be able to solve the problems of various diseases and improve our daily life.
"The key to effective reorganization of our genome and its provision of new useful molecular functions is to understand the principles of the simplest molecular forms of life in the past," the scientist sums up.
The original article by Cayetano-Anolies and Ibrahim Koch entitled "The Natural History of Molecular Functions on the Basis of Extensive Phylogenetic Analysis of Genetic Ontology Data" was published in the journal PLoS One.
The article is based on materials .
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