image: Polyploidy is in your heart and liver, in the vegetables you eat, in the rogue cells that cause cancer, and without it, humans wouldn’t exist. Yet only within the last few years have biologists begun to recognize its significance across the tree of life.
Credit: Dana Robinson
It’s in your heart and liver, in the vegetables you eat, in the rogue cells that cause cancer. Those who live in temperate regions are surrounded by more of it than people who live in the tropics, and without it, humans wouldn’t exist.
It’s called polyploidy, and only within the last few years have biologists begun to recognize its significance across the tree of life.
“It’s one of the most important biological processes that hardly anybody knows about,” said Doug Soltis, a distinguished professor at the Florida Museum of Natural History.
Soltis is one of 18 scientists who have received a combined $12.5 million grant from the National Science Foundation to establish the Polyploidy Integration and Innovation Institute. The grant is part of a broader initiative by the National Science Foundation to bring together scientists from disparate areas of expertise to work on pressing problems in biology.
“Polyploidy is a perfect topic for this sort of integration,” said Pam Soltis, a distinguished professor and curator at the Florida Museum and lead investigator on the project. Researchers with the institute will study the effects of polyploidy in plants and animals, from entire ecosystems down to organs and cells.
“We want to conduct a set of experiments that is consistent across organisms,” Doug Soltis said. “This is the first time we’ll be able to determine whether there are consistent rules that govern polyploidy.”
The institute will also use new and unique data management tools and prioritize community engagement to gain as much insight as possible, with eventual applications to agriculture, medicine and conservation, Pam Soltis said. Educators on the team, including the Florida Museum’s Brian Abramowitz and Stephanie Killingsworth, will take the knowledge generated by the institute and use it to implement a strategic communication and outreach campaign.
“The institute will guide high school curriculum development and teacher training; provide research experiences for undergraduates, graduate students and post-doctoral researchers; and offer training in science communication, while hosting local and international research conferences,” Pam Soltis said.
Polyploidy takes center stage after a century on the sidelines
At its most basic, polyploidy just means having more than the normal pair of matching chromosomes. Typically, when plants and animals undergo sexual reproduction, two sets of chromosomes — one from each parent — combine to create a new organism.
Humans have been aware of this concept since Austrian monk Gregor Mendel established the foundation of genetic inheritance by conducting experiments with pea plants. But occasionally, this process goes awry, and instead of a pair of chromosomes, offspring are endowed with additional chromosome sets in a process called genome duplication.
This happens frequently in plants, and for several decades, botanists were the only ones that took a significant interest in the subject. The process can be so prevalent that some plants carry around eight or more chromosome pairs packed tightly in their cells. What is the utility of all this extra genetic material? Scientists once thought it didn’t have much use at all. Then they discovered it was one of the most common ways new species are formed.
According to Doug Soltis, they’re still learning this. “My own view is there are hundreds of thousands of cryptic polyploid species that we have never recognized or scientifically named.”
Polyploidy has been implicated in the origin of seeds, flowers and several plant lineages, including nearly every cultivated plant humans grow for food.
For reasons that remain unclear, polyploidy also seems to be stratified on a global scale. There are fewer known polyploid species in the tropics than there are in colder regions, and the incidence of genome duplication appears to be higher at increased elevations.
It may also have serious implications for how well plants are able to cope with rapid climate change.
“Polyploidy is already known to shape the structure of biodiversity across the plant, especially since polyploids are often more successful in stressful environments,” said Robert Guralnick, co-principal investigator on the grant and curator of biodiversity informatics at the Florida Museum.
‘Polyploidy is everywhere’
Biologists later discovered that polyploidy wasn’t just restricted to plants. Animals had it, too. Nearly everything with a backbone can trace its origin to double genome duplication events that took place more than 450 million years ago. Similar duplications have occurred in fish, worms, insects, arachnids and mollusks.
“Polyploidy is everywhere,” Doug Soltis said. “It’s a giant iceberg, and we’re at the very tip.”
Scientists next discovered that polyploidy did much more than increase biodiversity. It’s also an important part of the way many plants and animals function — or malfunction. Polyploidy is present in roughly 37% of cancer types in humans. In other types of cancer, scientists think induced polyploidy may provide a cure.
Polyploidy pops up in various organs as well, where it plays a significant role.
“The cells in half of your heart are polyploid. Investigators are figuring out this gives them a higher metabolism, which is important for pumping blood,” Soltis said.
The medical community began realizing the importance of polyploidy in the early 2000s, but it was largely unaware that other biologists had been intently focused on the topic for many decades. A series of scientific conferences devoted entirely to polyploidy helped bring everyone together.
“It’s a case of not seeing what you don’t look for. We were all siloed, and there was a lot of surprise when people learned about what others were doing,” Doug Soltis said.
Just as genetics became its own field of study that transcended biological boundaries after Mendel laid out the laws of inheritance, polyploidy is poised to become a new specialty, one ripe for discovery and innovation. The Polyploidy Integration and Innovation Institute will help make this happen.
“There’s so much we don’t yet know,” Guralnick said. “What’s exciting and unusual about this effort is bringing together what we can learn from lab experiments about how polyploids perform under different conditions with patterns we see across landscapes. This knowledge is necessary for sustaining biodiversity and critical ecological services of value to society.”
Brad Barbazuk and David Miller of the University of Florida are also investigators on the grant. Other collaborating institutions are Cornell University, Duke University, the University of Kentucky, the University of Minnesota, the University of Mississippi, the University of Pittsburgh, Ghent University and the Max Planck Institute for Plant Breeding Research.