Researchers at Washington State University have pulled back the curtains on a mysterious plant protein that could change agriculture in a world overheated by climate change.
As higher temperatures across the earth bring drought and manic weather, the MAP20 protein could offer crops a fighting chance in desolate soil, said Andrei Smertenko, a biologist in WSU’s Institute of Biological Chemistry.
But when Smertenko and physiologist Karen Sanguinet in WSU’s Department of Crop and Soil Sciences teamed up to unearth the protein’s secrets six years ago, they didn’t think it could lead to solutions for climate change.
“Neither of us had funding for this at the beginning,” Sanguinet said. “It was a side project; high risk but high reward.”
MAP20 had been discussed as the potential target of a common herbicide, DBN, but its function was still unknown, Smertenko said.
Farmers had been using DBN for decades, and scientists didn’t know how it was working. When one team of researchers in Sweden proposed that DBN had been targeting the little-understood MAP20 protein, Smertenko and Sanguinet revved up to start their own project.
“We said, we know this protein’s important,” Sanguinet said. “So let’s break it, let’s mutate it and change its expression and see what happens.”
They deactivated a MAP20 gene. What they found was a change in the architecture of pits, a tiny structure in plants that allows water to move from cell to cell.
Like the human body is filled with capillaries – branching tubes that carry blood – plants, too, have a network of capillaries called vessels which move nutrients and water through the plant’s body.
During a period of drought, vessels fill with tiny air bubbles called embolisms. When that drought ends and water returns to the plant, the new fluids’ path from roots to shoots can be blocked by these embolisms.
When a bubble forms in one capillary, it will spread to neighboring capillaries, through the pit. Large pits mean air bubbles are more likely to move from one cell to another.
“Pits is an incredibly difficult system to study because they’re hidden inside the capillary,” Smertenko said. “So our understanding about the pit development is limited.”
What Smertenko does know about the microscopic openings is that increasing expression of MAP20 meant smaller pits for a plant and thicker pit membranes, which can protect crops from blockages during drought.
In their study, the survival rate of plants lacking MAP20 was significantly lower. Breaking MAP20 affected how the plant’s vasculature system developed, lowered yield and increased vulnerability to drought.
In the future, farmers in high-risk drought areas could use crops genetically engineered to increase MAP20 expression, Smertenko said.
“Farmers in the Palouse are doing pretty well with varieties adapted for this climate,” Smertenko said. “But in the central part of the state, the profit margin is very narrow.”
But it’s not a ready-to-go fix.
When there is soil moisture, plants benefit from larger pits, which can more easily move nutrients and fluids from cell to cell. Future studies will need to go deeper and look at variations in MAP20 expression between different plant species and populations.
“As a scientist you might want to say this is the next best thing and it will revolutionize agriculture, but the truth is this is just one piece of the puzzle and one part of the balance,” Sanguinet said.
The good news is that MAP20 plays a very specific role, meaning its effects can be analyzed and understood more directly than many other genes and proteins.
Many genes and proteins are pleiotropic, meaning they play a part in many different processes, Sanguinet said. With a pleiotropic protein, changing its expression can lead to unwanted side effects because the change won’t only affect the target process.
“You can even make an analogy with hydroxychloroquine,” Sanguinet said, referring to the controversial COVID-19 therapy. “It might be efficacious against COVID-19, but it negatively affects your heart, your skin and all these things. It’s pleiotropic. What you want is a really specific drug that only affects one thing.”
The next step will be to tease out the protein’s job in other plants, outside of the grass Smertenko and Sanguinet used in their study, Sanguinet said.
And while she’s excited to dig deeper into MAP20, climate change is barreling ahead. Studies are already reporting seasons starting and ending at different times than they once did. Dehydrated fields are a nearby reality, she said.
Scientists have to keep a step ahead, Smertenko said.
“It’s very important that we anticipate these changes and start to develop technologies and ideas now,” Smertenko said. “Then we can start to overcome this problem.”
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