There have been five mass extinctions of the Earth in its 4.6 billion-year history of geological evolution. The most famous and well-known is the most recent: the Cretaceous-Paleogene(K-Pg) biological extermination event (Figure 1), 66 million years ago, because it marked the end of the 160 million-year-old dinosaur era.
Figure 1. Cretaceous-Paleozoic Extinction Event (K-Pg) 66 million years ago
Current research has concluded that the main cause of the mass extinction was an asteroid about 10 kilometers in diameter that hit the Earth, leaving an impact crater with an average diameter of 180 kilometers. A large number of ancient geology, paleoenvironment and palaeontology and other aspects of evidence that this devastating event to the Earth’s ecosystem brought great disaster, resulting in a global dust cloud, shade the sky, in a few years or even hundreds of years to isolate the sun, low levels of light make it difficult for plants to carry out photosynthesis. Algae and land plants in the ocean are dying, the entire food chain is collapsing, and large animals are starving to death.
At the same time, global temperatures have plummeted, and cold ground temperatures make it difficult for seeds to germinate, leading to the extinction of many terrestrial plants. Three-fifths of species in the plant world also went extinct during this period, such as the giant naked plants and ferns that accompanied the dinosaur era. At present, the dominant species of quilt plants (also known as flowering plants) dominate the Terrestrial Ecosystem on Earth, with more than 350,000 species of species, rich in forms and diverse forms, distributed in almost all habitats.
So how did the quilt edgy plants survived the catastrophes of the Great Extinction period?
In 2009, a team of evolutionary genomicists Professor Yves Van de Peer found that during the K-Pg extinction, many branches of quilt plants had independent lysing events of ancient multiples (or whole genome doubling) events (Figure 2). Based on this, the researchers speculate that multiples may have been an important reason for the survival of many of the ancestors of existing quilt plants during the mass extinction. The discovery has caused a strong response, many internationally renowned scholars have paid great attention to it, and even some scholars have called it “one of the most exciting discoveries in the field of multiples over the past decade”.
Figure 2. Multiple branches of quilted plants have had ancient multifoldevents during the K-Pg extinction
When it comes to polysethes, I believe many people are no strangers, because many of the crops and important cash crops in our daily lives are polyploid plants formed in the near future after multiples, such as cotton, wheat, rape, sugar cane, bananas and watermelons. In fact, polysuptization refers to the process by which organisms double the genome to obtain more chromosomes. Multiplexing gives an additional “copy” of the genetic material of an organism, providing the original genetic material for evolution, often considered an “accelerator” of biological evolution. After the formation of polyploids, there are obvious advantages in many aspects, especially high biomass and cash crop yield, strong resistance, high efficiency of water fertilizer utilization.
Is polystening the main reason for helping quilt plants escape extinction? Current research focuses on the coupling of the two in time, and evidence of how multiples help quilt plants adapt to dramatic environmental changes has not yet been revealed. Different researchers on this issue have put forward different hypotheses.
In 2017, for example, Professor Yves Van de Peer put forward the idea of “adaptive” that polyploids have an adaptive advantage over the diphenoids in adverse circumstances; Professor Freeling suggests that asexual reproduction may act as a transition buffer for polyploids during environmental upheavals, and that polyploids are redouble and accurate subtractions are created when the environment is normal; Professor Soltis co-suggests the ecological niche hypothesis that drastic environmental changes significantly reduce the number of dicoccal species in ecosystems and provide ecological opportunities for the survival of polyploid species. However, these ideas are based on recent studies of polyploids, which in turn speculate on the possible adaptation strategies of guacons in the event of environmental changes. In short, these arguments are speculative and there is no clear evidence.
In November 2019, a team at the Institute of Plant Research of the Chinese Academy of Sciences gave a new explanation of how gudopoly can help quilt plants adapt to drastic environmental changes. We all know that polysuptization can duplicate all genes in the genome, greatly altering the composition of genetic material. So did the genetic material changes caused by the multi-multiplier events during the K-Pg extermination help the plants adapt to the dramatic environmental changes of the time?
Based on the above assumptions, the team selected 25 plant species with genome-wide data, representing different branches and exoplanets of quilt plant evolution (Figure 3), and conducted rigorous and detailed bioinformatics analysis to uncover clear evidence of multiples helping plants adapt to mass extinction events at the genetic base.
Figure 3. Polycocen events in the evolutionary history of quilt plants and their retained duplicate genes
Due to the long time of the ancient multiplier event, the clues left behind are complex, and it is not easy to accurately identify the duplicate genes that remain after multiples. To this end, the team used a variety of methods to build a complete set of analysis process, accurate identification of quilt plant evolutionary history occurred after the ancient multiplier event retained by the repeated genes.
Secondly, by analyzing the function of the repetitive genes that were jointly preserved after the occurrence of multiplex events by different branches of the K-Pg biological extinction period, it was found that the polytimes that occurred during that period jointly retained the repetitive genes that adapted to the dramatic environmental changes during the great extinction period. It is shown that these genes may have helped plants cope with the pressure of choice that was then stressed in the environment (Figure 4).
In addition to the K-Pg period of extinction (-66 Ma), the team analyzed two other periods of history in which multiples were concentrated (-120 Ma and .lt;20 Ma), and, at the same time, The study found that the repetitive genes retained after multiples of these periods were functionally consistent with the environmental selection pressure sesame in a particular historical period (Figure 4).
Figure 4. Repeated genes retained after multiples in the three historical periods were involved in coercive response.
The team also analyzed in-depth and detailed adaptive-related gene regulatory networks and used transcriptome data to build a gene co-expression network. The discovery of key regulatory genes that were jointly preserved after the genome-wide doubling of the Cretaceous-Paleogenetic extinction period has reshaped and complicated genetic regulatory networks adapted to severe environmental changes (cold and dark) and may have enhanced plant resilience to environmental stress (Figure 5).
The results of this study reveal the pressures of ancient polysedons to help plants cope with paleoenvironment choices from the level of genetic regulatory networks. In addition, the study found that retention of duplicate genes in transcription factor families was analyzed in detail, and found that retention in different transcription factor families after multiples had a preference. Families of transcription factor genes that tend to be highly retained play an important role in plant response to environmental stress after multiplesing events, while low-reserved or unreserved transcription factor gene families play a major role in conservative biological processes.
Figure 5. Evolutionary model of the post-cold stress control network during the period of biological extinction
The retention of specific stress-related repetitive genes after multipleification promotes the complexity of the quilt plant regulatory network in response to drastic environmental changes, which in turn enhances the adaptability of the quilt plant. This finding not only validates previous assumptions, but also confirms that polyxing does help quilt plants adapt to environmental upheavals during the mass extinction period, but also provides clear genetic evidence of how multiples enhance the adaptive evolution of plants.
In short, even the dinosaurs were extinct in the harsh environment during the K-Pg extinction period, and polyploid plants were able to survive and reproduce “tenaciously”, to a large extent reflecting the significance of polysusing in adaptive evolution. Especially in today’s global climate change, figuring out the genetic mechanism of multi-fold adaptation advantages has important theoretical guidance and practical application value for biological evolution, species protection and genetic breeding.