Scientifically Speaking | A molecular tweak that could make farming environmentally friendly
Modern agriculture’s critical challenge is to feed a growing global population while reducing the environmental footprint of fertilizer use.
Every year, farmers around the world spread over 200 million tons of chemical fertilizers across their fields. These fertilizers help feed billions, but at the steep environmental cost of polluted waterways, greenhouse gas emissions, and degraded soils. Plants have internal communication systems that connect them with helpful microbes in the soil. Now, scientists have discovered a way to tap into these networks to offer us a way to break our overreliance on synthetic fertilizers.
The key lies in enhancing the natural partnerships of crop plants with beneficial soil microbes. These microbes help plants in crucial ways. Soil microbes have acted as microscopic allies that have helped plants thrive since they first colonized land hundreds of millions of years ago. Some capture nitrogen from the air and convert it into plant food, while others extend the plant's reach into the soil to gather water and minerals.
In a new study published in Nature, researchers led by Myriam Charpentier have found a way to genetically fine-tune the ability of plants to form these partnerships. The breakthrough focuses on a remarkable protein called cyclic nucleotide-gated channel (CNGC15). CNGC15 sits in the membrane surrounding the cell's nucleus and controls the flow of chemical signals. Together with its partner protein DMI1, CNGC15 controls the communications system that allows plants to recognise and form partnerships with nitrogen-fixing bacteria and nutrient-gathering fungi.
This molecular “traffic police” is particularly special because it controls the flow of calcium, which is crucial to plants. By making a precise change to just one amino acid in the researchers found that they could dramatically improve plants' ability to form these beneficial partnerships. Normally, when beneficial microbes approach the roots of a plant, they release chemical signals that trigger CNGC15 to generate rhythmic pulses of calcium ions, like a secret handshake. These calcium pulses help plants recognize and welcome helpful microbes.
But here's where it gets interesting. By changing just one tiny part of the protein- a single amino acid building block- they could make plants generate these calcium signals spontaneously, without waiting for the microbial greeting. Modified plants became more proactive in seeking out beneficial relationships rather than waiting to be approached.
The results were remarkable. Plants with this modified CNGC15 became super-collaborators, engaging in more mutually beneficial partnerships with microbes and absorbing more nutrients. They formed more partnerships with both nitrogen-fixing bacteria and beneficial fungi called arbuscular mycorrhizae, leading to better nutrient uptake, even in conditions where plants typically ignore their microbial helpers. The modified plants also produced higher levels of flavonoids, chemical compounds that act like welcome signs to attract beneficial microbes.
Perhaps most exciting is what happened when the researchers applied this discovery to wheat, one of the world's most important food crops. Even in nutrient-rich field conditions that typically suppress these natural partnerships, wheat plants with the modified CNGC15 showed enhanced colonisation by beneficial fungi.
This is important because normally, when soil is rich in nitrogen and phosphorus, plants reduce their reliance on microbial partnerships, essentially "turning off" these collaborations. But the CNGC15 mutation allows plants to sustain these relationships even when nutrients were abundant in the fertilizer-rich conditions of modern farms. This hints at the tantalizing prospect of being able to reduce our reliance on chemical fertilizers while maintaining robust crop yields.
Modern agriculture faces a critical challenge. We need to feed a growing global population while reducing the environmental footprint of fertilizer use. Chemical fertilizers are effective, but they are also major contributors to water pollution and greenhouse gas emissions. The excessive use of nitrate and phosphate fertilizers are of particular concern, since these chemicals can harm ecosystems far beyond the fields where they're applied.
This discovery offers a potential path forward by increasing the natural ability of plants to acquire nutrients through biological partnerships that evolved over millions of years. Instead of forcing crops to rely on synthetic fertilizers, we could one day be able to strengthen their alliances with soil microbes. The mutation identified by the research team is especially promising because it works even under intensive farming conditions, where these beneficial partnerships typically struggle to form.
Scientists will now have to investigate how this genetic modification performs across different crop varieties and environmental conditions. They'll need to determine whether enhanced microbial partnerships can truly match the yields achieved with conventional fertilization methods. There are also regulatory hurdles to clear when dealing with genetic modifications in agriculture. But through an ingenious tweak to an ancient natural system of collaboration between plants and microbes, there’s a possibility to address one of modern agriculture's greatest challenges.
Anirban Mahapatra is a scientist and author, most recently of the popular science book, When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine. The views expressed are personal.