Stress response compounds that are widespread in animals are found in plants

A The molecule, made famous for its association with human heart disease and the ability of marine animals to survive high pressure conditions, is also made by plants, researchers report this week (May 19) in Advances in science. As with animals, trimethylamine N-oxide (TMAO) helps plants deal with stressful conditions, the study found. The authors have already licensed the discovery to a company working to commercialize TMAO to increase farm yields.

“Nobody had previously published that plants have TMAO in their tissues,” says study co-author Rafael Catalá from the Centro de Investigaciones Biológicas (CIB) Margarita Salas in Madrid.

The new study arose from previous work in which Catalá and his colleagues looked for genes in the model plant Arabidopsis thaliana the expression of which has been changed by exposure to the cold. It turned out that a gene they found codes for a type of enzyme called flavin-containing monooxygenase (FMO), which is called FMOGS-OX5. In further analyzes reported in the current study, the team found that the expression of several other FMO Gene is also selected Arabidopsis in response to cold.

FMOs are known to produce TMAO in animals in response to a variety of stressors. The team wondered what the link was between the FMOs and the facility’s cold response and used nuclear magnetic resonance to look for wild-type TMAO Arabidopsis. They found it and confirmed its presence using liquid chromatography-tandem mass spectrometry. The team also verified that FMOGS-OX5 can generate TMAO from its precursor TMA in vitro.

In animals, TMAO acts as an osmolyte, a type of molecular cell that is used to maintain the properties of their fluid and prevent proteins from being misfolded under conditions such as high salt concentrations. To see if it plays a similar role in plants, Catalá and his colleagues covered Arabidopsis Roots with tunicamycin, a compound that allows proteins to unfold, as can happen under abiotic stress conditions such as cold or lack of water. The tunicamycin made the roots grow more slowly, but this effect was lessened when the roots were grown in medium that was supplemented with TMAO, the researchers report.

When the researchers constructed Arabidopsis overexpressing FMOGS-OX5The plant also increased the expression of 184 other genes, many of which had previously been linked to responses to abiotic stressors, the authors report. The application of TMAO to wild type plants had a similar effect on gene expression, although it did not change FMOGS-OX5Expression level suggesting that TMAO acts downstream of FMO to improve the expression of stress response genes.

To find out if TMAO is widespread in plant species, the team also looked for tomatoes, corn, barley, and a relative of tobacco and found it was present in all of them. In addition, their TMAO levels increased when the plants were exposed to conditions of low water, high salinity, or low temperature (with the exception of barley, where TMAO did not increase in the high salinity test, but under the other conditions). Spraying or watering tomato plants with a solution containing TMAO made them visibly healthier, with more leaves, when exposed to any of the three stressful conditions.

According to Catalá, externally applied TMAO has the potential to be “a very powerful tool for agriculture”. He and the newspaper’s senior writer, Julio Salinas, also of CIB Margarita Salas, have filed patents for the agricultural use of TMAO, which is being commercialized by Plant Response. The company’s field tests have shown good results, adds Catalá.

Paul Verslues, who studies the response to crop drought at Academia Sinica in Taipei, Taiwan, asks whether TMAO will be agriculturally useful. “The TMAO protection of the protein folding can be relevant for the survival of severe stress by the plants, but it is not known whether it is also beneficial for the protection of the plant growth in less severe drought or salinity stress,” he writes in an E -Mail to The scientist. The stresses the researchers put on the plants were too severe to reflect the agricultural conditions, and further experimentation would be needed to determine whether TMAO also helps plants cope with milder stress conditions.

Verslues also cites other reservations about the study’s results, including this one Arabidopsis made to overexpress FMOGS-OX5 had a greater stress tolerance than wild-type plants but did not accumulate more TMAO, suggesting that FMOs “can produce another compound that promotes stress tolerance” in addition to TMAO. In addition, the authors did not take the step of turning off all plants FMO Genes to test whether these genes are really needed for TMAO production in plants.

Catalá argues that the study’s key finding, that TMAO is present in plants and “plays a key role in plant tolerance to abiotic stress”, is without testing such mutants. And he says it’s likely FMOWhile s produce other compounds that are involved in the stress response, the paper shows that they are involved in making TMAO and that TMAO increases stress tolerance.

Aleksandra Skirycz, a plant biologist at the Boyce Thompson Institute for Plant Research who was not involved in the study, calls it “a beautifully crafted story.” For them, the “really exciting part of this job is that you have a molecule that acts as an osmolyte for protection [and] At the same time, it would probably have other signaling functions ”, a phenomenon she calls“ moonlight ”. It’s not yet clear how TMAO affects gene expression, says Catalá, and that will be one path the group can follow in the future.

In the biomedical literature, TMAO occurs in a negative rather than a positive context, as high levels in the blood of patients are associated with an increased risk of blood clots. Studies have shown that gut microbes break down choline, a nutrient found in high amounts in meat, to produce TMAO and related compounds, creating a mechanistic link between a meat-rich diet and risk of heart attack and stroke. Catalá says it is not at all clear what effects the finding of TMAO in plants could have on human nutrition and health.

Correction (May 23): In the original version of this article, TMAO was incorrectly referred to as protein. The scientist regrets the mistake.



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