‘It’s a giant iceberg, and we’re at the very tip’: Why polyploidy is taking centre stage after a century on the sidelines

By Oliver Morrison

- Last updated on GMT

Polyploid plants with more chromosomes (strawberries have eight sets of chromosomes) often exhibit increased stress tolerance compared to their diploid counterparts. Getty/Jonathan Knowles
Polyploid plants with more chromosomes (strawberries have eight sets of chromosomes) often exhibit increased stress tolerance compared to their diploid counterparts. Getty/Jonathan Knowles

Related tags plant breeding genetics

The concept of polyploidy has hit the headlines. But what is it – and why are scientists keen to learn more about its potential impact in agriculture?

David Friedberg recently revealed to an exited agtech world details about Ohalo Genetics’s radical plans to produce hardier more productive crops. This involves artificially inducing the concept of polyploidy – where an organism has more than two sets of chromosomes – to bring new levels of precision and speed to plant breeding.

Ohalo’s technology works by disenabling the reproductive circuits in each parent plant. Normally, a random half of the genes of each parent go to the offspring. But by switching off this reproductive circuit, and effectively controlling polyploidy, the offspring plant gets 100% of the genes from each parent. The fact the plant has more genes means it has more changes of inheriting a gene that will allow it to overcome or manage a stress. Ohalo’s early trials have seen “insane” yield gains of “50% to 100% or more” compared to regular plants​, said Friedberg.

Why is there is a growing interest in polyploidy?

Fresh on the heels of this announcement is the news that a new $12.5 million National Science Foundation grant has been given to establish the Polyploidy Integration and Innovation Institute at the Florida Museum of Natural History. Researchers with the institute will study the effects of polyploidy in plants and animals, from entire ecosystems down to organs and cells. The aim is that these insights will lead to eventual applications in a host of areas including agriculture, conservation and medicine.

Polyploidy is in our hearts and livers, in the vegetables we eat, and in the rogue cells that cause cancer. But it’s only within the last few years that have biologists have begun to recognise 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.

Meanwhile, the more we do know about it, the more we foresee its positive impact in agriculture. For example, Soltis told AgTechNaviagtor​, it appears that controlling polyploidy can help in combating environmental stresses and improve crop resistance to pests and diseases. But it is not entirely clear how polyploidy can alleviate stress responses. “Somehow, having extra gene copies can promote novel responses,” he said.

Nearly all crops are polyploid. There is therefore great interest, said Soltis, in understanding the benefits and drawbacks to polyploidy for engineering the next generation of crops.

He predicts a huge role for greater understanding about polyploidy in agriculture and also the new bioengineering economy. “If engineered polyploid cells can generate much more of a particular needed chemical compound than can diploids,” he said. “This will be used more and more in the bio economy to make medicines… you name it.”

The role of polyploidy in producing climate-resiliant crops

At its most basic, polyploidy simply 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.

GettyImages-1256617919 (1)
Plants with larger numbers of chromosones can adapt to a wider range of environmental conditions thanks to their ability to develop favorable physiological traits such as larger organs, increased photosynthetic capacity, and enhanced tolerance to biotic and abiotic stresses. Hexaploid wheat (with six sets six sets of chromosones) shows better fitness under salt stress compared to its tetraploid and diploid relative. Image: Getty/Aldona

According to 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.

And for reasons that remain unclear, 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.

Again, this 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,” added Robert Guralnick, co-principal investigator on the grant and curator of biodiversity informatics at the Florida Museum.

Polyploidy is everywhere, but there is so much we don't know

“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.”

“Polyploidy is everywhere,” Soltis said. “It’s a giant iceberg, and we’re at the very tip.”

The institute will use new and unique data management tools and prioritize community engagement to gain as much insight as possible. “We want to conduct a set of experiments that is consistent across organisms,” Soltis said. “This is the first time we’ll be able to determine whether there are consistent rules that govern polyploidy.”

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