Understanding Genome Duplication in Flowering Plants
Credit: David Chapman/Alamy
Recent research indicates that extra copies of genetic material may have enabled flowering plants to endure mass extinctions, including the event that led to the demise of the dinosaurs.
A pivotal discovery reveals that angiosperms—flowering plants like daisies, grasses, and fruit trees—survived major ecological upheavals throughout Earth’s history due to accidental genome duplications. While multiple genomes can typically pose an evolutionary challenge, these tumultuous periods may have provided opportunities for angiosperms to flourish, allowing them to dominate today’s plant life.
Generally, sexually reproducing species possess two sets of chromosomes—one inherited from each parent. However, many plants, especially angiosperms, exhibit a phenomenon known as polyploidy, characterized by having multiple chromosome sets due to failures in meiotic division. Some plants, such as potatoes and specific wheat varieties, can have up to four or even more sets of chromosomes.
About one-third of current angiosperms are classified as polyploid. Researchers, including Hengchi Chen from the University of Göttingen, Germany, suggest that historical instances of genome duplication are relatively infrequent, though. “Most polyploid organisms went extinct during prolonged evolutionary transitions,” Chen remarks.
Chen and his research team sought to understand why certain ancient genome duplications in angiosperms took hold while others did not. They studied the genomes of 470 angiosperm species, constructing an evolutionary tree that illustrated 132 distinct instances of genome duplication over 150 million years.
These duplications clustered around nine significant prehistoric epochs, from 108 million to 14 million years ago, often coinciding with substantial environmental shifts or geological events, including climate changes, shifts in oxygen levels, and mass extinctions like the Cretaceous asteroid impact that eliminated non-avian dinosaurs. During these unstable periods, polyploid plants experienced significant advantages.
Although polyploidy can be a hindrance—impeding growth and complicating reproduction with non-polyploid species—these times of environmental stress may have facilitated the rise of polyploid plants. Factors such as extreme weather conditions could trigger reproductive failures, fostering an increase in ploidy levels, Chen explains. Additionally, polyploid plants exhibit heightened resilience to stressors like drought and salinity, allowing their extra genes to adapt to rapidly changing environments. As competitors faltered, new opportunities arose within these evolving ecosystems.
“Originally small and often overshadowed in their populations, polyploid individuals gained access to more resources and demonstrated adaptive advantages in response to stress,” Chen details, highlighting their improved survival rates.
The adaptive flexibility and redundancy of the genomes in angiosperms, he concludes, may be key drivers behind their evolutionary success.
Meanwhile, researchers like Pamela Soltis at the Florida Museum of Natural History in Gainesville, emphasize the need for large-scale genomic analyses across a wider array of angiosperm species to refine these findings. “This study is ambitious for its scale, yet the 470 species examined reflect just a fraction of the nearly 400,000 known angiosperm species,” Soltis states, noting the rapid pace at which new genomic data is becoming available.
Source: www.newscientist.com
