The secret behind the poisonous mushroom "toxin synthesis"
September 07, 2018 Source: Chinese Journal of Science and Technology
Window._bd_share_config={ "common":{ "bdSnsKey":{ },"bdText":"","bdMini":"2","bdMiniList":false,"bdPic":"","bdStyle":" 0","bdSize":"16"},"share":{ }};with(document)0[(getElementsByTagName('head')[0]||body).appendChild(createElement('script')) .src='http://bdimg.share.baidu.com/static/api/js/share.js?v=89860593.js?cdnversion='+~(-new Date()/36e5)];Wild mushrooms may contain toxins and cannot be eaten. It has become common sense, and the world's most poisonous mushrooms are hidden in the three genera of amanita, Helmets and ring-shaped mushrooms. In fact, as early as more than one hundred years ago, people have discovered that the toxic mushrooms in the above three genera are far apart, belonging to three different families in taxonomy, but they can all synthesize the same class. Toxin: amanita peptide. However, how the “Amanita Peptide Production Line†has evolved has been a puzzle.
Recently, the Fungal Lichen Diversity and Adaptive Evolution Team of the Key Laboratory of Plant Diversity and Biogeography of East Asia of the Kunming Institute of Botany, Chinese Academy of Sciences has unveiled the mystery. The mechanism for synthesizing “Amanita†is far beyond imagination. Luo Hong, an associate researcher at the Kunming Institute of Botany, Chinese Academy of Sciences, told the Journal of the Chinese Academy of Sciences: "The creepy amanita is not the 'original' of these mushrooms, but the 'borrowing' from an unrelated ancient mushroom."
"Grass boat borrows arrows" to produce toxins
Amanita has an important contribution to scientific research. Some edible amanita and highly toxic amanita are very similar in appearance and difficult to distinguish, which is an important cause of poisoning.
Like penicillin producing penicillin, amanita also has a number of genetic "toxin production lines" for the synthesis of the most toxic mushroom toxin "Amanita peptide". Toxins are very useful for mushrooms and protect mushrooms from animal damage so that their seeds mature and spread. Creatures living in the same environment can exchange genes and DNA directly. This process is called horizontal gene transfer. There are many DNA sequences in the human body from viruses, which are also caused by horizontal gene transfer.
"These poisonous mushrooms are using this method to make a copy of their beneficial toxin gene 'cottage' and add it to their own genes, just like 'grassboat borrowing arrows', and arm themselves in an instant. Other mushrooms may take tens of thousands of years to evolve, and these mushrooms will take no effort," Luo Hong said.
The study also found that the "borrowing arrow" is achieved from the step of the mushroom to the Helmet and then to the amanita. Although the amanita finally obtained the "secret recipe" for the synthesis of toxins, it has evolved the ability to synthesize new toxins through genetic improvement. Therefore, its toxicity exceeds that of Helmets and ring-shaped mushrooms, and it has become a well-deserved "poison king." 90% of the mushroom poisoning deaths are related to it.
Twists and turns of exploration
Luo Hong told reporters that the discovery of the mechanism of amanita toxin synthesis is a matter of nearly eight or nine years. "At first, we thought that all fungal cyclic peptides were completed by non-ribosomal peptide synthesis pathways. Instead of directly encoding the genes, we first synthesized huge proteins and enzymes from the organisms, and then spliced ​​the free amino acids together. But the experiment proves that this idea does not work in amanita," Luo Hong said.
Just as scientific research has entered the “dead endâ€, genome sequencing has opened up a new direction. Luo Hong said that after the genome was sequenced, the researchers did not find the enzyme originally conceived. "At this time, we realized that the synthetic pathway of the amanita cyclic peptide may be directly encoded by the gene."
After the research ideas were determined, Luo Hong and the research team spent ten years studying the related scientific issues from different angles and methods. This paper, which analyzes the evolution mechanism of amanita peptides, reports for the first time in the world the evolution history of the “Amanita Peptide Production Lineâ€.
Luo Hong told reporters that fresh samples of amanita, Helmets and genus Mushrooms are difficult to collect, and most laboratories cannot collect these three types of mushrooms at the same time, but Kunming plants have unique advantages in this respect.
“The ring-shaped mushroom is difficult to collect, and its growth has strict latitude, temperature and altitude requirements. For example, the northern regions such as Inner Mongolia, Xinjiang, and Gansu grow. When collecting these highly poisonous mushrooms, our students sometimes grow in the ground. It took several weeks to find the sample," Luo Hong said.
Luo Hong often handles highly toxic mushrooms in the experiment. He said: "Inadvertently ingesting highly toxic mushrooms during the experiment will not be fatal. The most dangerous thing is to use some reagents to increase skin permeability when extracting toxins. If the reagents get on the skin, they will be exposed to toxins and toxins. It will quickly enter the human body at dozens of times."
Even in the face of various dangers, the research team is still sticking to the initial focus of scientific research, and continues to work on poisonous mushroom science. "Do not eat on the head wearing a hat, a waist skirt, and a shoe that still wears shoes on the feet" is the summary and refinement of the poisonous species of the amanita.
Mushroom poisoning is difficult to prevent and control, patients often do not know what kind of poisonous mushrooms they have eaten, and clinical diagnosis often leads to misdiagnosis. In this regard, Luo Hong said: "From eating mushrooms to poisonous hair, there is a 12-hour false recovery period. When the injury does not occur, you can replenish water through a large number of infusions to protect the liver and kidneys while diluting and metabolizing toxins. In high-risk areas of amanita toxins, it is necessary to regularly use emergency liver care products, such as milk thistle health products, and timely use can significantly alleviate the disease."
Continuously reveal the ecological function of amanita
Previous studies have confirmed that the poisonous amanita has probably appeared in the dinosaur era, and it can be speculated that the "borrowing" gene is given to the ancient species of amanita earlier. It is speculated that the oldest amanita-producing mushroom has disappeared in the long history of evolution, but this “toxin production line†is preserved in amanita, Helmetum, and ring-shaped mushroom, and is passed on in the offspring. Going down, forming a unique evolutionary mechanism to help it adapt to the environment, survive and multiply.
Since ancient times, humans have had the custom of collecting mushrooms, and the increase in population has led to such activities becoming more frequent, and the threat to the survival of mushrooms is increasing. "This may form a natural choice invisibly, strengthen the survival and competitiveness of highly toxic mushrooms, which may be an important reason for the frequent incursions of poisonous amanita in recent years, causing frequent poisoning incidents." Luo Hong Say.
It has long been discovered in the study of amanita: the cyclic peptides synthesized by amanita are not all toxins, and one of them is also an "antitoxin", which can offset the damage of toxins and protect the organisms.
In fact, there are not many species of amanita mushrooms before they form a highly toxic one. But when it co-produced with the trees to produce toxins, it quickly proliferated a series of new species.
"This is an explosive growth. We suspect that it must be related to the new cyclic peptide. In order to improve its viability, it has been functionally subdivided, not only to defeat microbes, but also to generate signaling molecules and provide antibiotics, so the amanita peptide The ecological function needs to be continuously researched to reveal the secret." Luo Hong said.
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