Stanleya pinnata
Stanleya pinnata, or "prince's plume," takes up large amounts of selenium from the soil. Danita Delimont/Getty Images
At first glance, the long, thin leaves and pale green shoots of Stanleya pinnata, a plant native to the Rocky Mountains, can make it seem like just another member of the Brassica family—mustard and broccoli’s eccentric cousin. For a few weeks each spring, the plant sprouts a bushy clutch of bright-yellow flowers on the tip of each stem, giving it the nickname “prince’s plume.”
But come a little closer, and you might start to notice something odd. The soil in a three-foot radius around the plant is bare—a “death zone” where nothing else can grow. And though not everyone can smell it, some people will detect an unpleasant odor in the air, like something rotting. That’s why Antony van der Ent, a plant scientist who grows Stanleya in his greenhouse at Wageningen University & Research in the Netherlands, tries to avoid handling the plant directly.
“You can touch it, but your fingers will smell for days,” he said, wrinkling his nose as he showed off the facility, where rows of seedlings grow in small pots, on a warm day in August.
Stanleya at a greenhouse at Wageningen University & Research in the Netherlands
Plant scientist Antony van der Ent grows Stanleya in his greenhouse at Wageningen University & Research in the Netherlands. Diana Kruzman
Van der Ent is an expert in hyperaccumulators, plants that have evolved to take up large amounts of specific minerals from the soil and store them in their leaves and stems. In the case of Stanleya pinnata, that mineral is selenium, an element found in high concentrations in the soils of its native Colorado. Along with depositing the selenium in its biomass, Stanleya also converts it into selenide gas. That makes the plant difficult to work with in a laboratory setting because this gas gives off a strong smell, but it’s just a small setback for van der Ent, who is raising Stanleya pinnata to study its ability to uptake selenium. He’s hopeful that eventually, unlocking its secrets could help solve selenium deficiency, a health problem that plagues the Netherlands as well as other regions of Europe, such as Scandinavia.
Stanleya pinnata doesn’t need selenium to survive, although scientists believe the plant has evolved the ability to accumulate the mineral as a defense mechanism against predators; high concentrations of selenium can be deadly. But humans, as well as other mammals, need trace amounts of selenium—between 40 and 70 micrograms per day—for proper thyroid function and to help the body’s immune system fight off the risk of cancer.
While most people get enough selenium through the crops they eat, like wheat, beans and lentils, up to one billion people living in areas with selenium-poor soils, including much of Northern Europe, are deficient—a number that’s likely to increase as the climate changes. A 2017 study by Swiss researchers predicted that 66 percent of croplands around the world would see a decrease in selenium concentrations by the end of the century, as lack of rainfall makes some areas too arid for the mineral to dissolve while more intense rainfall in others washes it from the earth.
Hoping to stave off a global health crisis, scientists are now working to breed a new generation of crops that are better at absorbing selenium. To do so, van der Ent is planning to use genes from selenium hyperaccumulators he discovered in Colorado and Australia to modify everyday crops like rapeseed, another member of the mustard family. Similar research is taking place in Spain, Turkey and China as part of a larger global strategy called biofortification that seeks to make food more nutritious and to improve the health of vulnerable populations.
“Rising carbon dioxide levels will exacerbate nutrient deficiencies, potentially pushing hundreds of millions of people into deeper malnutrition,” said Wolfgang Pfeiffer, a project manager and scientist for HarvestPlus, a nonprofit that promotes the spread of biofortified crops around the world. “This makes biofortification an increasingly important intervention in the fight against micronutrient malnutrition.”
Other methods exist to tackle vitamin and mineral deficiencies, like dietary supplements (think daily multivitamins) and industrial fortification, which involves adding elements like iron to staple foods like rice and flour. Supplements are already widespread among wealthier nations, while governments and aid organizations in developing countries distribute fortified foods to more vulnerable populations.
Biofortification is more difficult to implement initially because of the high costs of research and development that go into breeding new varieties of plants. But in some ways, it’s also easier; people who need vitamins don’t have to remember to take a pill (or be able to afford one), and foods like flour don’t have to go through the extra step of industrial fortification before they’re sold, because the wheat would already contain the minerals within the plant’s cells.
Nonprofit organizations like HarvestPlus and the Global Alliance for Improved Nutrition are already working to bring biofortified crops like beans, cassava, sweet potatoes, rice, lentils and wheat to countries like Bangladesh, Pakistan, Nigeria, Tanzania and Rwanda. Most of these are not genetically modified; instead, they’re conventionally bred, or crossed with plants that are naturally higher in essential minerals.
About One Billion People Are Deficient in Selenium. Genetic Engineering Could Change That
Golden Rice is a Vitamin A-rich variety invented in the 1990s by plant geneticists Ingo Potrykus and Peter Beyer. International Rice Research Institute
Genetically modified biofortified foods like “golden rice,” a Vitamin A-boosting variety invented in the 1990s by plant geneticists Ingo Potrykus and Peter Beyer, have faced opposition in countries like the Philippines due to fears about their effects on health and the farming of local varieties. Some development experts have criticized biofortification as an approach to solving problems like vitamin deficiency or micronutrient malnutrition, arguing that the focus should instead be on making sure people have access to a diversified diet.
“Since rice is a poor source of vitamins and minerals, any child eating a rice-only diet will be sick,” anthropologist Glenn Davis Stone and social science researcher Dominic Glover wrote in the Conversation in 2020. “Genetically modifying rice to contain beta carotene is at best a band-aid for extreme cases of [vitamin A deficiency], not a corrective for a widespread problem.”
Supporters of biofortification, though, stress its importance while agreeing that it should complement a diverse diet.
“Biofortification is a critical component of food system approaches to reducing micronutrient deficiencies,” Pfeiffer said. “However, it is just one tool in a broader strategy—there is no single solution to the problem.”
Biofortification, though, is essential for selenium. The human body can only metabolize the mineral in the form of selenocystine, an amino acid that is difficult and expensive to produce artificially. That means it can’t be added to foods like flour through industrial fortification the way other minerals like zinc or iodine can. But as van der Ent discovered, plants like Stanleya pinnata collect selenium in exactly this form, making it relatively simple to genetically modify crops that will deliver the mineral to the people who eat them.
The hard part is determining exactly which genes to transfer, though. First, scientists have to understand where plants store selenium—whether the leaves, stems, roots, flowers or seeds—and then attempt to trace the exact genetic code that directs them to do so. That’s important if they want to eventually modify crops like rapeseed, which is mainly harvested to produce oil from its seeds, van der Ent explained. His goal is to learn which genes direct Stanleya to store selenium in its own seeds, making for an easier genetic transfer to rapeseed.
Finding the specific genes that drive hyperaccumulation is a complex task, said Michela Schiavon, a biologist at the University of Turin in Italy who studies selenium biofortification and is currently working with van der Ent as a visiting researcher at Wageningen University. A previous project she worked on in Colorado found some promising candidates, also using Stanleya pinnata; but when those genes were transferred to other plants, they didn’t start hyperaccumulating selenium, sending the research back to the drawing board.
“The black box is understanding how these plants work,” Schiavon said.
Antony van der Ent's greenhouse
Van der Ent is studying other hyperaccumulators in his greenhouse. Diana Kruzman
Another area of research is the concentration of selenium, which varies from plant to plant and even within the life cycle of one organism. Another plant van der Ent is studying, an Australian species called Neptunia amplexicaulis, stores a much higher concentration of selenium in its young leaves than its older leaves.
It’s a delicate balance, because although selenium is essential for human health, it’s also highly toxic in larger doses, causing a syndrome called selenosis that leads to fatigue, hair loss, nail deformities and neurological damage.
“We have to not only try to modify these plants to accumulate selenium, but to not accumulate too much,” van der Ent said. “It’s a question of expressing these particular genes to the right level.”
Researchers like van der Ent and Schiavon expect that they’ll stay busy with these questions for years to come as climate change supercharges interest in biofortification and selenium research more broadly. One country that’s leading the charge is China, which lacks selenium inhalf of its agricultural soils. In 2019, the country opened its first national selenium research and development center in the city of Wuhan; four years later, it launched a Selenium Innovation Laboratory at Xi'an Jiaotong-Liverpool University near Shanghai.
There, scientists are studying how microbial communities could affect the uptake of selenium in hyperaccumulator plants, mainly using Cardamine hupingshanensis, which, like Stanleya pinnata, is a member of the Brassica family and resembles watercress or mustard greens. Native to China’s Wuling Mountains, Cardamine has long been consumed as apickled condiment called sui mi ya cai, making it an even stronger candidate for biofortification—and, hopefully, a less smelly one.
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Diana Kruzman | READ MORE
Diana Kruzman is a journalist reporting on religion, the environment and urbanism. Her work has been featured in the New York Times, the Christian Science Monitor and Gizmodo, among other publications.
Filed Under: Agriculture, Engineering, Food, Food Science, Genetics, Health, Nutrition, Plants