Extreme plant grows faster under stress

Extreme plant grows faster under stress

The extreme plant Schrenkiella parvula © José Dinneny

If conditions are too dry, too salty, or too cold, most plants will grow poorly and eventually die. The extreme plant Schrenkiella parvula, on the other hand, thrives even better under what are actually deadly conditions. A new study now shows that a plant hormone that is released in response to environmental stress plays an important role in this. While it gives other plants the signal to save resources, it stimulates growth in Schrenkiella parvula. The results could help establish similar signaling pathways in crops, making them more tolerant of extreme environmental conditions.

Climate change means that crops in many places have to cope with increasingly unfavorable conditions. Extreme weather events such as long periods of heat and drought are increasing and endangering the harvests of conventional food crops. Researchers are therefore working on developing plants that are better able to withstand extreme conditions, using both classic plant breeding methods and green genetic engineering. Findings about so-called extremophytes, i.e. plants that naturally grow under extreme conditions, are helpful here.

Growth under extreme conditions

A team led by Ying Sun from Stanford University in California has now taken a closer look at such an extreme plant. The researchers studied Schrenkiella parvula, a plant from the cruciferous family that is native to Turkey, among other places, on the shores of the extremely salty Lake Tuz. With a salinity of 32.9 percent – almost ten times as much as the North Sea – Lake Tuz is one of the saltiest lakes in the world, and the soil in the shore area is correspondingly salty.

Schrenkiella parvula apparently evolved in such a way that it not only survives under these conditions, but actually grows faster, Sun and her team show. “Most plants produce a stress hormone in response to extreme conditions, which acts like a stop signal for growth,” explains her colleague José Dinneny. In temporarily inhospitable conditions, reducing resource consumption in this way allows a plant to survive until conditions improve again. “But in this extremophyte, the stress hormone acts like a start signal,” says Dinneny. “In response, the plant accelerates its growth.”

Same hormone, different effect

To find out why the stress hormone has a different effect in Schrenkiella parvula than in other plants, Sun and her team analyzed both the genome of the extremophyte in comparison to related cruciferous plants such as cabbage, broccoli, beets and oilseed rape, as well as the hormone signaling pathways involved. The main difference in the response to environmental stress was found not to be due to Schrenkiella parvula genetics, but to an altered hormone signaling pathway in response to the hormone abscisic acid (ABA).

While in other cruciferous plants ABA activates genes that slow or stop growth, in Schrenkiella parvula it activates genes that ensure increased growth. “This rewiring of the network at least partially explains why we get these different growth responses in stress-tolerant species,” said Dinneny. The researchers hope to introduce such extremophyte-style rewiring to crops, thereby making them more stress-tolerant. “In the face of climate change, we cannot expect the environment to stay the same,” says Ying Sun. “Our crops have to adapt to these rapidly changing conditions. If we understand the mechanisms that plants use to tolerate stress, we can help them do it better and faster.”

Agricultural Perspectives

Increased stress tolerance would not only be desirable for food crops, but also for the production of biofuel from oilseeds such as rapeseed. “You could grow bioenergy crops on land that is not suitable for growing food – for example, on agricultural fields with degraded soils or with high salinity due to improper irrigation,” says Dinneny. Appropriately genetically adapted oil crops could potentially be grown on land that would otherwise have to be abandoned.

“In the work presented here, we have identified genes whose gene regulators may have been the target of natural selection for stress tolerance,” the authors write. “Thus, they could be useful candidates for influencing the response to abiotic stress through gene editing.” In future studies, Sun and her team want to include other cruciferous plants in the analyzes and thus find out to what extent the findings could be used in agriculture.

Source: Ying Sun (Stanford University, California) et al., Nature Plants, doi: 10.1038/s41477-022-01139-5

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