Photosynthesis under attack and what cells can do about it
Researchers are looking at how plants and algae can protect themselves from attacks from within
Photosynthesis isn’t perfect, in fact, it can create byproducts that cause the plant to take one step back for every two steps forward. Researchers are looking at how photosynthetic organisms – like plants and algae – can protect themselves from attacks from within.
When algae are under stress from adverse conditions such as too high temperatures, they generate photosynthetic byproducts known as reactive oxygen species, or ROS. ROS can turn on the algae, harming the chloroplast, the place within a plant or algal cell where photosynthesis occurs.
The cell deploys countermeasures to protect itself from damage. Researchers in the MSU-DOE Plant Research Laboratory, or PRL, want to know how the plant senses the damage and signals for these countermeasures to be deployed.
“Based on our findings we are proposing a mechanism by which plants produce a very specialized lipid that is essentially the ‘check engine light’ for photosynthetic membranes,” said T.J. Nicodemus, postdoctoral researcher in the Benning lab and first author of the paper.
In their paper, published in Plant Physiology, they hypothesize that there is a specialized fatty acid that becomes damaged thereby telling the plant unfavorable conditions are present. The researchers found that the gene responsible for this special fatty acid encodes two proteins: FAD4, which is responsible for the specialized fatty acid, and LCI2, which is a protein induced under low CO2 stress. The researchers showed that it serves as a membrane anchor for a ROS mitigating enzyme, ascorbate peroxidase, allowing it to associate with the photosynthetic membrane.
The researchers looked at mutants of the algae Chlamydomonas reinhardtii with and without the FAD4 and LCI2 proteins. They observed how these mutants couldn’t deploy ROS countermeasures to the membrane, sustained more damage and grew worse under stress conditions than their wild-type counterparts.
“These findings are only the tip of the iceberg for what is undoubtedly an extremely complex new area of study,” Nicodemus said. “For a long time, people have been hypothesizing how plants sense and signal lipid damage in the chloroplast, now we have a whole new area of REDOX biochemistry to study.”
By studying photosynthetic organisms like Chlamydomonas, researchers can better understand the plants we all rely on for food and oxygen.
“The ultimate goal is to understand how plants deal with stress and light conditions with a hope for creating plants better capable of producing, whether that be food, biofuels or industrial products,” Nicodemus said. “This finding brings us one step closer.”
Despite the progress described in this paper, the researchers are still a long way away from fully understanding how lipid-based ROS signaling works in detail. As always, there is more work to be done.
“The work described in this paper exemplifies the collaborative environment of the Plant Research Laboratory,” said Christoph Benning, University Distinguished Professor in the PRL, the Department of Biochemistry & Molecular Biology and the Department of Plant Biology. He is the corresponding author of this study. “The PRL brings together different experts to provide basic insights into the complex mechanisms of how plants capture and convert sunlight through photosynthesis and adapt to a changing environment.” The other PRL co-authors are Daniela Strenkert, Stefan Schmollinger, Barb B. Sears and John E. Froehlich.
This work was funded by the Office of Basic Energy Sciences of the United States Department of Energy (Grant DE-FG02-91ER20021) and by MSU AgBioResearch (MICL02632).