news

한어Русский языкEnglishFrançaisIndonesianSanskrit日本語DeutschPortuguêsΕλληνικάespañolItalianoSuomalainenLatina

On July 15 (Monday), the main contents of the well-known foreign scientific website are as follows:

Nature website (www.nature.com)

Scientists discovered for the first timeMammothAlmost complete chromosome

In a skin sample from a woolly mammoth that died under mysterious circumstances about 50,000 years ago in the Siberian tundra, researchers have discovered chromosomes preserved in their original three-dimensional (3D) structure, a finding previously unseen in ancient times.DNAThe study was considered impossible.

The team also revealed the spatial organization of mammoth DNA molecules and the active genes in the skin, one of which is responsible for giving the mammoth its hairy appearance. The study was recently published in the journal Cell.

About 40 years ago, scientists discovered that fragments of DNA can survive in ancient specimens, including Egyptian mummies thousands of years old. But over time, DNA degrades and suffers chemical damage, making it nearly impossible to reconstruct the three-dimensional structure of the genome from these fragments. Because it was assumed that the three-dimensional structure of DNA would be lost over time, no one had attempted to study chromosome organization in ancient cell nuclei.

To challenge this assumption, the researchers conducted a nine-year search for well-preserved ancient DNA samples and finally found almost complete chromosomes in a skin sample of a woolly mammoth unearthed in the Siberian permafrost. The mammoth died 52,000 years ago. The researchers analyzed the structure of the mammoth chromosomes and revealed the folding of the DNA molecule and its spatial structure in the cell nucleus - two features that are crucial in determining which genes are turned on and how long they are turned on.

The method in the paper could also help researchers assemble a complete mammoth genome, said the director of biosciences at Colossal Biosciences, a U.S. biotechnology company that is working to resurrect the mammoth.

Science Daily website (www.sciencedaily.com)

1. How do cold-resistant plants adapt to the environment: Polyploid plants can accumulate structural mutations

Cold-resistant plants like Cochlearia are well adapted to the cold climate of the Ice Age. As the climate alternated between cold and warm, they evolved many species of Cochlearia, which also led to a proliferation of genomes. Evolutionary biologists from the University of Heidelberg in Germany, the University of Nottingham in the UK and the University of Prague in the Czech Republic investigated the effects of this genome duplication on the adaptive potential of plants. The results show that polyploid plants - species with more than two sets of chromosomes - can accumulate structural mutations with local adaptations that allow them to occupy ecological niches again and again.

The genus Chamaeme in the family Cruciferae split from its Mediterranean relatives more than 10 million years ago. While their direct descendants specialized for drought stress, Chamaeme plants conquered cold and arctic habitats at the beginning of the Ice Age 2.5 million years ago. In an earlier study, the researchers investigated how Chamaeme plants repeatedly adapted to rapidly alternating cold and warm periods over the past 2 million years. Among other things, some of the newly emerged cold-adapted Chamaeme plants developed different gene pools that came into contact with each other in cold regions. The exchange of genes gave rise to populations with multiple sets of chromosomes. As the size of their genomes continued to shrink, they were able to occupy ecological niches in cold regions again and again.

The current study sequenced the diploid reference genome of a species of the Alpine plant family, Coleus, and reconstructed a so-called pan-genome. This connects different genome sequences together and thus shows genetic relationships between individuals and other species.MutationsAn analysis of more than 350 genomes from different species of the genus Coleus with different chromosome numbers showed that polyploids actually exhibit locally adaptive genomic structural variation more frequently than diploid species.

These structural mutations are masked by additional genome duplications and are therefore somewhat shielded from selection pressures, as accumulation of structural variation can also lead to loss of function. Through their model, the team further demonstrated that polyploidy-specific structural variation also occurs in genetic regions that may play an important role in future climate adaptation.

2. AI can speed up the analysis of cardiac MRI images, leading to better heart disease treatment

A research team from the Universities of East Anglia, Sheffield and Leeds in the UK created an artificial intelligence (AI) model that uses AI to analyze heart images from magnetic resonance imaging (MRI) scans.

Whereas it might take doctors 45 minutes or more to analyze an MRI image, the new AI model only takes seconds.

While other studies have investigated the use of AI in MRI image analysis, this latest AI model was trained using data from multiple hospitals and different types of scanners and tested on different groups of patients from different hospitals. In addition, the AI ​​model provides a complete analysis of the entire heart by showing a view of all four chambers, while most earlier studies focused on only the two main chambers of the heart.

"This innovation could lead to more effective diagnoses, better treatment decisions, and ultimately improved outcomes for heart disease patients," the researchers said.

3. A simple method can save livesBacteriophageEasy to transport and share

Bacteriophages, which destroy bacteria naturally, often when antibiotics fail, could change the course of medicine and agriculture, especially as antibiotic resistance grows worldwide. Each form of phage is specialized to attack a specific form of bacteria, allowing phages to specifically target infections while leaving beneficial bacteria alone.

A major challenge in harnessing the enormous potential of phages is how to make them more easily and quickly available. Currently, there is no central repository of phages, only local phage collections that exist in places such as research laboratories and private clinics. To make matters worse, live phages must be suspended in vials of liquid and refrigerated or frozen, which makes storage of phages cumbersome and hinders the efficient transportation and sharing of phage collections.

Researchers from McMaster University and Université Laval in Canada have collaborated to develop a simple new method to store, identify and share bacteriophages, making them more accessible to patients who need them.

They developed a dry storage platform that plays a major role in their new user-friendly system to quickly match specific infections with the phages that can stop them.

At the heart of the new system is a novel pill-shaped medium that stores phages without the need for refrigeration and combines them with a medium that produces a visible glow when the phages respond to a target infection.

The new technology enables phages to be stored at room temperature for months until they are needed, and combines biobanking and testing laboratories in one small package.

The team's work is described in a paper recently published in the journal Nature Communications.

Scitech Daily website (https://scitechdaily.com)

1. A century-long biological experiment reveals the genetic secrets of barley

A long-term study dating back to 1929 has revealed important insights into the evolution of barley, showing its adaptation to different environments and the significant impact of natural selection. The research highlights the limits of evolutionary breeding and underscores the need for further exploration to improve crop yields.

The survival of cultivated plants after their dispersal into different environments is a classic example of rapid evolutionary adaptation. For example, barley, an important Neolithic crop, became widespread after domestication more than 10,000 years ago and became a major source of nutrition for humans and livestock in Europe, Asia, and North Africa over thousands of generations. Such rapid expansion and cultivation subjected barley to strong selection pressures, including artificial selection for desirable traits and natural selection forced to adapt to a variety of new environments.

Although previous studies of early barley varieties have determined some of its population genetic history and mapped genetic loci that contributed to its spread, the speed and overall dynamics of these processes are difficult to determine without direct observation. Using the Complex Hybridization II (CCII) experiment, one of the oldest and longest-running evolutionary experiments in the world, researchers have observed local adaptation in barley over nearly a century.

Although there were thousands of barley genotypes at the start of the experiment, the study shows that natural selection drastically reduced this diversity, eliminating almost all of the founding genotypes, leading to the dominance of single clonal lineages that form most populations. This transition occurred quickly, with asexual lines established by the 50th generation. According to the results, this successful lineage was mainly composed of alleles originating from Mediterranean-like environments. In addition, the study shows that the target genes of selection play an important role in climate adaptation, including strong selection on the timing of reproduction.

2. The secret of the excellent performance of the new organic semiconductor NFA

Solar energy plays a vital role in the transition to a clean energy future. Current silicon-based solar panels have their limitations - they are expensive and difficult to install on curved surfaces. Researchers have developed alternative materials to address these shortcomings of silicon, and the most promising of these are so-called "organic" semiconductors. These are carbon-based semiconductors, which are abundant on Earth, cheap, and environmentally friendly.

One drawback of organic solar cells is their low photoelectric conversion efficiency, about 12%, compared to 25% for single-crystal silicon solar cells. But the recent development of a new class of organic semiconductors, non-fullerene acceptors (NFAs), has changed this paradigm. Organic solar cells made with NFAs can achieve efficiencies approaching 20%.

Despite their outstanding properties, the scientific community still does not understand why NFAs are so significantly superior to other organic semiconductors. In a groundbreaking study published in the journal Advanced Materials, researchers have discovered a microscopic mechanism that partially explains the extraordinary performance of NFAs.

Key to the discovery were measurements the researchers made using an experimental technique called time-resolved two-photon photoemission spectroscopy, or TR-TPPE. This method allowed the team to track the energy of excited electrons with sub-picosecond temporal resolution (a picosecond is one trillionth of a second, or 10^-12 seconds).

The researchers believe that this unusual process can occur on a microscopic scale due to the quantum behavior of electrons, which allows an excited electron to appear on several molecules at the same time. This quantum weirdness coincides with the second law of thermodynamics, resulting in an unusual energy gain process. (Liu Chun)