Some plants have a remarkable coping mechanism when they experience stress: they pump their tissues full of a molecule called dimethylsulfoniopropionate, or DMSP, which gives cells a kind of armor against factors like salt stress and drought.
Now, researchers studying DMSP-rich species of grass have not only identified the genes behind the production of this molecule, but crucially have found a way to transfer these benefits to other crops like tomatoes, enabling them to cope with salt stress significantly better than they did before.
Their research—which incorporates a large body of work ranging from field and lab experiments, to genetic sequencing and engineering—began with a salt-resilient plant called cordgrass. This plant grows wild in coastal salt marshes in the UK and elsewhere, and is known to accumulate large amounts of DMSP in its tissues, similarly to some marine algae and bacteria which need to manage their exposure to lots of salt.
Other plants, including some crops, also produce DMSP, but at much lower levels than cordgrasses. The researchers believed that the higher levels in this saltmarsh plant may hold the key to unlocking greater potential in other plants.
To find out, they compared the genes of two cordgrass species with those of other plants. “We tracked the enzyme activity associated with DMSP production and then managed to link that back to the DNA sequence to identify the specific genes involved,” says Ben Miller, lead author on the new study and associate professor in the school of biological sciences at the University of East Anglia. They found that in cordgrasses those genes are typically highly-expressed, which increases the activity of the enzymes involved in the production of DMSP, and amps up the availability of this molecule in plant tissues.
When the researchers then ran tests growing cordgrass plants in a greenhouse experiment, they found that those watered with saltwater had notably higher levels of DMSP in their tissues—supporting the idea that DMSP accumulates in response to salt stress, among other things.
But how to bring these benefits from a wild species into agricultural crops that are also under increasing strain from salt stress and drought? That was the researchers’ next challenge—and with the newfound genetic knowledge, they had a solid starting point.
To test their idea they chose a plant called benthi, a close relative of tobacco that is commonly used in research. Benthi is known to produce DMSP, albeit in tiny amounts. But the researchers showed that if they artificially over-expressed three of the genes that are involved in the enzyme activity, they could significantly elevate levels of the DMSP molecule in the tobacco plant. What’s more, the DMSP-intensive plants were more tolerant to salt- and drought-stress than the controls, even showing an increased root biomass under the more stressful conditions.
The scientists also tested out a shortcut. For this set of experiments they took a batch of tomato plants—but instead of tweaking their genetics, they applied DMSP molecules as a treatment directly to the soil that the tomato plants were growing in. Tomatoes are also known to produce small quantities of DMSP, but when the plants were exposed to salt stress, those that had been treated with DMSP in the soil accumulated the molecule in their leaves at rates four- to six-fold greater than the salt-stressed plants that had not been treated with DMSP. These tomatoes, it seems, were absorbing the molecule to give them greater protection against highly-saline soils.
This extra armor also helped them survive: while saline soils decreased biomass in all tomato plants, in the DMSP-treated tomatoes the biomass decline was roughly half that of the plants that didn’t receive DMSP in the soil.
There could be real significance to these findings if the researchers can amp up the molecule’s production or availability in some of the world’s biggest crops like wheat, which currently make small amounts of DMSP, says Miller. “The discovery gives us a fundamental understanding about how plants tolerate stress and may ultimately allow us to improve the tolerance of crops, like wheat, to stress such as salinity and drought.”
Miller et. al. “Elucidation of Spartina dimethylsulfoniopropionate synthesis genes enables engineering of stress tolerant plants.” Nature Communications. 2024.
Photo by Станислав Вершинин/Adobe Stock
