‘Extreme’ plants grow faster in the face of stress

When the weather is too dry, salty or too cold, most plants try to save resources. They send out fewer leaves and roots and close their pores to hold water. If circumstances don’t improve, they eventually die.

Schrenkiella parvula is a plant that can grow – and even thrive – in extremely salty conditions. Researchers at the Dinneny Lab are studying this plant to understand this particular adaptation and how it might be able to modify other plants to withstand similarly stressful environments. (Photo credit: José Dinneny)

But some plants, known as extremophytes, have evolved to cope with harsh environments. Schrenkiella parvula, a scrawny, branching member of the mustard family, not only survives in conditions that would kill most plants—it thrives in them. It grows on the shores of Lake Tuz in Turkey, where the concentration of salt in the water can be six times higher than in the ocean. In a recent article in nature plantsfound researchers at Stanford University Schrenkiella parvula actually grows faster under these stress conditions.

“Most plants produce a stress hormone that acts like a stop signal for growth,” said José Dinneny, associate professor of biology at Stanford and lead author of the study. “But with this extremophyte, it’s a green light. In response to this stress hormone, the plant accelerates its growth.”

Dinneny and his colleagues are studying Schrenkiella parvula to better understand how some plants cope with challenging conditions. Their findings could help scientists develop plants capable of growing on poorer quality soil and adapting to the stresses of climate change.

“In the face of climate change, we cannot expect the environment to stay the same,” said Ying Sun, a postdoctoral fellow at the Salk Institute who received her PhD from Stanford and is the lead author of the article. “Our plants have to adapt to these rapidly changing conditions. If we understand the mechanisms by which plants tolerate stress, we can help them do it better and faster.”

An unexpected reaction

Schrenkiella parvula is a member of the Brassicaceae family, which includes cabbage, broccoli, turnips, and other important food crops. In areas where climate change is expected to increase the duration and intensity of droughts, it would be valuable if these crops were able to survive or even thrive during these droughts.

When plants are exposed to dry, salty, or cold conditions — all of which produce water-related stress — they produce a hormone called abscisic acid, or ABA. This hormone activates certain genes and essentially tells the plant how to respond. The researchers studied how several plants of the Brassicaceae family, including Schrenkiella parvula, replied to ABA. While the growth of the other plants slowed or stopped, the roots of Schrenkiella parvula grew significantly faster.

Schrenkiella parvula is closely related to the other plants in the study and has a very similar sized genome, but ABA activates different sections of its genetic code to produce entirely different behavior.

“This rewiring of this network at least partially explains why we get these different growth responses in stress-tolerant species,” Dinneny said.

picture one S. parvula Root taken with a confocal microscope. (Image credit: Prashanth Ramachandran)

develop future cultures

An overview of Ying Sun’s research by Neil E. Robbins II, PhD ’17, a former PhD student at Dinneny Lab. This comic was originally published on April 14, 2017 by Neiler Comics. (Image credit: Neil E. Robbins II)

Understanding this stress response — and how to manipulate it in other species — could help more than just food crops, Dinneny said. Schrenkiella parvula is also related to several oilseed species that have the potential to be developed and used as sustainable sources for jet fuel or other biofuels. If these crops can be adapted to harsher environmental conditions, more land would be available for their cultivation.

“They want to grow bioenergy crops on land that’s not suitable for growing food — say, an agricultural field that has degraded soil or accumulated salt due to improper irrigation,” Dinneny said. “These acres are not prime agricultural real estate, but rather lands that would otherwise be abandoned.”

Dinneny and his colleagues continue to study the reaction network that could help plants survive in extreme conditions. Now that you have an idea of ​​how Schrenkiella parvula maintains its growth despite limited water and high salinity, they will attempt to engineer related plants so that they are able to do the same by optimizing which genes are activated by ABA.

“We’re trying to understand what the secret sauce is for these plant species – what allows them to grow in these unique environments, and how we can use that knowledge to evolve specific traits in our plants,” Dinneny said.

Other Stanford co-authors on this study are research associate Lina Duan, postdoctoral researcher Prashanth Ramachandran, and graduate student Andrea Ramirez. Additional co-authors are from Louisiana State University and the Salk Institute for Biological Studies. Dinneny is a member of Stanford Bio-X.

This work was funded by the US Department of Energy, the Carnegie Institution for Science, the National Science Foundation, the Rural Development Association of South Korea, and the HHMI-Simons Faculty Scholars Program.

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