The latest model defines the evolution of snake venom

Phoenix Science and technology news on December 10, Beijing time, according to the Science Daily, the current technology that describes the main genes inside the mouth of a snake or lizard has changed the way scientists define animals as poisonous If oral glands are able to express some of the 20 gene families associated with toxins, the species is defined as toxic However, a new study from the University of Texas at Arlington challenges this definition, and these studies also establish a new model to describe how snake venom is produced The study, published in the journal Molecular Biology and evolution, is based on a comparative analysis of related genes or "gene families" in different parts of tissues of the golden python, also known as the python molurus bivittatus By Todd, assistant professor of biology, University of Texas at Arlington Castoe's team, which also includes researchers from the University of Colorado and the United Kingdom, found that the level of the so-called toxin gene family contained in the boa constrictor's oral gland was very similar to the level of the same gene in the boa constrictor's brain, liver, stomach and other organs Scientists say the discovery shows the function of the snake venom gene before it evolved into a snake venom It also shows that the expression of genes related to snake venom in the oral glands of snakes or lizards is not enough to fully define whether a species is toxic or not "The study of snake venom is very common, because it is very important for the treatment and understanding of snake bites, as well as the potential application of snake venom in drug development However, all previous studies have focused on the glands, where snake venom is produced before it is released " Castor said "As for what happened to other parts of the body, there is no definite research This is the first study to use the snake venom genome to study other parts of the snake's body " Understanding the evolution of snake venom can help scientists to develop better antivenom and provide knowledge of human gene evolution Castor said that with the improvement of gene analysis ability, scientists have found more and more evidence to support a long-term theory The theory is that highly toxic proteins evolved from non-toxic genes that perform common functions in other parts of the body, such as regulating cell functions or digesting food "These results suggest that the gene or the transcription gene previously interpreted as a 'toxin gene' may be just a common 'housekeeping' gene, mainly involved in maintaining the normal metabolism of many tissues." Stephen mackessy, co-author of the study and professor of biology at the University of North Colorado, said "Our results also show that snake venom and snake venom delivery systems do not have a single ancient origin, but evolved independently from several separate reptile lineages." Castor is the lead author of a 2013 study that mapped the genome of the golden python Python is not defined as toxic, even though it has some of the same genes that evolved into snake venom in other species The difference is that the venom gene family of vipers, such as rattlesnakes and cobras, has been expanded to have multiple copies of this gene, and some copies have evolved into genes that can produce highly toxic proteins "Before the snake venom gene family expanded and redistributed, the non-toxic Python was isolated from the snake evolutionary tree So anacondas represent a window into snakes before the evolution of snake venom " Castor explained "Studying it will help us picture how these gene families in many vertebrates, including humans, have evolved into genes that encode deadly toxins." Jacobo Reyes Velasco, a graduate student at castor laboratories, is the lead author of the latest study Other collaborators include Daren card, Audra Andrew, Kyle shaney, Richard Adams and drew schield of the school of biology at the University of Texas at Arlington, and Nicholas of the school of Tropical Medicine in Liverpool, UK Casewell) The team investigated 24 families of snake venom related genes shared by pythons, cobras, rattlesnakes and lizards (Gila monster) The traditional view of snake venom evolution is that it is a core snake venom system developed at a certain point in the evolution process of snakes and lizards This is the famous toxicofera evolutionary branch hypothesis, and the evolution of serpents, also known as the advanced (caenophidian) snakes, occurs after this evolutionary branch As for why evolution selects 24 genes from more than 25000 genes to form highly virulent coding genes, the current explanation is very scarce "We believe that this study will provide an important baseline for future research, help snake venom researchers better understand the process leading to the generation of toxic molecular mixture in snake venom, and define the molecules that are important for killing prey and the pathology of human snake venom bite patients." In studying Python species, the team found several common features that are different from other genes in the gene family related to snake venom Compared with other Python gene families, snake venom gene family "has a lower overall expression level, only in very few tissues has a medium level of expression, and the gene expression level shows the greatest variability in all tissues." Castor said "Evolution seems to be based on the location (or whether) of gene expression and the degree of expression to select the specific genes that evolved into snake venom." Castor explained Based on these data, a new model including three steps of snake venom evolution is proposed First of all, these potentially toxic genes default to be present in oral glands, because although they are expressed at a low level, they are more consistently expressed throughout the body Secondly, the expression level of these genes in oral tissue is higher than that in other parts of the body, because it is beneficial to select these genes in oral gland naturally Finally, as snake venom evolved to be more and more toxic, the expression of these genes in other organs gradually decreased, thus limiting the secretion of these toxins in other body tissues to produce potentially harmful effects In the first mock exam, the team called the intermediate to near neutral evolutionary supplement (SINNER) model They say that different levels of venom in snakes and other animals can be traced back to the changes of different species or different genes in the same species from the beginning to the end of the sinner model Castor said the next step in the study would be to investigate the genome of the venomous snake to investigate the reliability of the sinner model For now, castor and his team hope the findings will change the way species are defined as toxic "More evidence is needed to define what is snake venom and what species are poisonous These findings provide a new perspective for us to think about when we observe the oral glands of snakes " (compiled by / Yan Yan Liu Xing)