How will ‘stressed-out’ plants weather climate change?

Plants can’t complain. Often the only way to tell that they are not doing well is to see them wilt and wither. Yet in a world where extreme temperatures, especially heat, are set to become far more common, plants, too, will be “stressed out,” researchers say.

A team of scientists at the Salk Institute for Biological Studies in the United States notes that we can tell how plants will respond to environmental stressors if we know where to look. And where to look is into a gene known as GUN 1, which integrates several chloroplast-to-nucleus retrograde signaling pathways.

Among its other functions, GUN1 is responsible for how proteins are made in damaged chloroplasts. And so it can provide us with answers as to how plants respond to stress, the researchers explain in a new paper, which was published in the Proceedings of the National Academy of Sciences.

Plant-cell structures called chloroplasts convert energy from sunlight into chemical energy through the process of photosynthesis. Under normal circumstances the cell nucleus relays information to chloroplasts so that a steady production of energy is maintained. When environmental stressors begin to affect a plant, however, chloroplasts start sending alarm signals back to the cell nucleus.

“Plants often experience environmental stressors, so there must be a chloroplast-to-nucleus communication pathway that helps the plant know when to conserve energy when injury occurs,” says Xiaobo Zhao, the study’s first author. “GUN1 turns out to play a big role in this.”

The researchers discovered that the gene GUN1 links up with another protein called MORF2, which is a key component of a plant’s RNA editing complex. GUN1 does so in order to affect the efficiency of RNA editing during chloroplast-to-nucleus communication in damaged chloroplasts.

“Greater activity of MORF2 led to widespread editing changes as well as defects in chloroplast and leaf development even under normal growth conditions,” the researchers note. “During periods of stress and injury, MORF2 overproduction also led to disruption of chloroplast-to-nucleus communication.”

The researchers now want to find out what process is employed at the cellular level in plants to effect changes in the RNA editing changes in chloroplasts. Their aim is to see how these modifications alter the ability of a plant to respond to environmental stresses like increased heat.

Such knowledge isn’t simply academic. Understanding how we can boost plants’ ability to withstand the effects of climate change better could help us ensure crops remain robust even in exceedingly inclement weather. “Climate change holds the potential to affect our food system dramatically,” stresses Prof. Joanne Chory, director of the Plant Molecular and Cellular Biology Laboratory at Salk.

“When plants are stressed, like in a drought, they produce lower crop yields,” Chory says. “If we understand how plants respond to stress, then perhaps we can develop a way to increase their resistance and keep food production high.”