Plants are also stressed


Plants are also stressed

LA JOLLA – (April 19, 2019) What will a world of three degrees of temperature be like? How will plants come out in the most extreme climatic conditions? When experiencing stress or damage from multiple sources, plants use chloroplast-to-core communication to regulate gene expression and help them cope.

Now researchers at the Salk Institute have found that GUN1 – a gene that integrates numerous pathways of retrograde chloroplast signaling – also plays an important role in the way proteins are produced in damaged chloroplasts, providing a new insight into how plants respond stress. The article was published in Annals of the National Academy of Sciences (PNAS) on April 15, 2019, and can help biologists create plants that can withstand environmental stressors.

"If we understand how plants respond to stress, maybe we can develop a way to increase their stamina." "If we understand how plants respond to stress, we can develop a way to increase their resistance. " maintain high food production, "says Professor Salk Joanne Chory, director of the Laboratory of Cellular and Molecular Plant Biology and senior author of the paper.

In plant cells, structures called chloroplasts convert sunlight energy into chemical energy (photosynthesis). Typically, the cell nucleus transmits information to the chloroplasts to maintain constant energy production. However, in a stressful environment, chloroplasts send an alarm back to the cell nucleus using retrograde signaling (creating a communication feedback loop between the chloroplast and the nucleus). This SOS provides a response that helps regulate gene expression in chloroplasts and in the nucleus to optimize the energy production of sunlight.

Previously, Chory's laboratory identified a group of genes, including GUN1, that influence the expression of other genes in the cell when the plant undergoes stress. GUN1 accumulates under stressful conditions, but the exact molecular function of GUN1 has been difficult to decipher so far.

"Plants often experience environmental stressors, so there must be a communication pathway between the chloroplast and the nucleus that helps the plant save energy when the injury occurs," says Xiaobo Zhao, first author and postdoctoral fellow at Chory's lab. "GUN1 turns out to play a big part in this."

To understand how GUN1 regulates chloroplast-core communication, scientists observed functional and nonfunctional GUN1 plants under pharmacological treatments that could damage chloroplasts. In plants without GUN1, gene expression changed, as did RNA editing in chloroplasts. (RNA editing is a modification of RNA that alters the identity of nucleotides so that information on mature RNA differs from that defined in the genome by changing the instructions for the production of proteins.) Some areas of RNA had more editing and other locations had less editing – suggesting that GUN1 plays a role in the regulation of chloroplast RNA editing.

After further analysis, the team unexpectedly discovered that GUN1 associates with another protein, MORF2 (an essential component of the plant RNA editing complex), to affect the efficiency of RNA editing during chloroplast communication to the nucleus in chloroplasts. The greater activity of MORF2 led to generalized editing changes as well as defects in the development of chloroplasts and leaves, even under normal growth conditions (see image). During periods of stress and injury, overproduction of MORF2 also led to interruption of communication between the chloroplast and the nucleus.

"Together, these findings suggest a possible link between chloroplast communication to the nucleus and chloroplast RNA editing, which are important regulatory functions for flowering plants, especially during stress," says Chory, a researcher at Howard Hughes Medical Institute and holder of Howard H. and Maryam R. Newman President in Plant Biology.

The researchers then plan to examine the mechanism of how RNA editing changes in chloroplasts activate the signals that can be retransmitted to the nucleus, and how these modifications alter the plant's ability to respond to stress.


Other authors included Jianyan Huang, a postdoctoral fellow in Chory's laboratory.

The work was funded by the US Department of Energy (DE-FG02-04ER15540) and the Howard Hughes Medical Institute.

About the Salk Institute for Biological Studies:

Every cure has a starting point. The Salk Institute embodies Jonas Salk's mission of daring to turn dreams into reality. Its world-renowned and award-winning scientists explore the very foundations of life, seeking new understandings in neuroscience, genetics, immunology, plant biology, and more. The Institute is an independent non-profit organization and an architectural landmark: small by choice, intimate by nature and fearless in the face of any challenge. Whether cancer or Alzheimer's, aging or diabetes, Salk is where cures begin. Learn more at:

This story was published in: 2019-04-20. To contact the author, use the contact details in the article.


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