Please tell us about yourself
When she is not student teaching or attending class, University doctoral candidate Manjula Mummadisetti is solving the puzzle of protein structures to increase knowledge of photosynthesis, and her research now can be read in a nationally acclaimed scientific journal.
Mummadisetti discovered the interaction of two protein subunits that aid in the evolution of oxygen during photosynthesis using a technique called cross-linking. Cross-linking allows researchers to discover the specific binding locations of amino acids between proteins.
Mummadisetti’s groundbreaking finding is the result of years of scientific research and something her predecessors tried but were unable to achieve.
What did you study?
Mummadisetti did her Bachelor of Science (B.Sc.) in Chemistry, Microbiology and Botany from Kasturba Gandhi Degree College for Women and Masters in Biochemistry from Osmania University. She then did her Masters and PhD from Louisiana State University in Biochemistry, Nanotechnology and Molecular Biology
How does your work benefit the community?
A world without plants would be a world without oxygen, uninhabitable for us and for many creatures. We know plants release oxygen by absorbing carbon dioxide and breaking down water using sunlight through the process of photosynthesis. However, we know little about the mechanics of how plants create oxygen during photosynthesis. A breakthrough that will help advance our understanding of this critical ecological process was made recently by scientists at LSU.
“Without photosynthesis or oxygen, basically all recognizable life that we see in our landscape would be gone: no animals, no plants,” said Terry Bricker, Moreland Family Professor in LSU’s Department of Biological Sciences.
What were the challenges?
“I tried several other projects in regards to photosynthesis before this one that just didn’t work,” Mummadisetti said. “Then I picked up this project, which had some preliminary data but had been stalled for some time, and I liked it, so I chose it as my Ph.D project.”
Mummadisetti said she, too, failed when she first began the project in 2013. It was her perseverance and mentor Terry Bricker, University Moreland Family professor, who kept her going and led her to this accomplishment.
Mummadisetti said she gained endurance and technique training for this project from a project she conducted in 2011 concerning photosynthesis and a different protein.
“Still, the beginning phases of this — my most recent project — was rough due to my lack of expertise with new techniques and simply because the project didn’t work,” Mummadisetti said. “I went back during my general exam hoping to get something out of it, and that’s when [Dr. Bricker and I] found out the cross-linking had worked and that I had enough data to start writing a paper.”
Tell us about your work
A graduate student in his lab, Manjula Mummadisetti, led this latest study that examined the cellular system responsible for creating oxygen during photosynthesis called Photosystem II. She analyzed two proteins that are critical to creating oxygen and modeled how they connect and interact, building upon previous information and her latest research. Their paper, titled “Use of protein cross-linking and radiolytic footprinting to elucidate PsbP and PsbQ interactions within higher plant Photosystem II” will be published this week online in the Proceedings of the National Academy of Sciences.
“This discovery means a lot for photosynthesis research. People have wanted to know about this for a very long time. We didn’t have these techniques and scientists were unable to find how these proteins connect,” Mummadisetti said of her first published scientific research paper.
One principle in biochemistry is that a protein’s structure determines its function. By creating a 3D model of these two critical plant proteins, Mummadisetti advances our knowledge about their structure, which can lead to a better understanding of how these proteins function. In her experiments, she used spinach from a grocery store because of its abundance. She isolated chloroplasts, the food factory of plants, and treated them with a chemical detergent to extract a high concentration of Photosystem II, the system within a plant that creates oxygen. She then used high-resolution mass spectrometry to see where the two proteins overlap and connect.
Bricker compares this process to putting a puzzle together where you can’t see or touch the pieces.
“We looked at thousands of puzzle parts and a relatively small number of these were useful for identifying what’s going on,” he said.
Then, based on their analyses, Bricker and Mummadisetti built a 3D computer model of the two Photosystem II proteins, which are called PsbP and PsbQ.
“Frankly, this is the very first paper that shows a direct association between PsbP and PsbQ,” Bricker said. “Because of Manju’s work, we now know how PsbP and PsbQ interact and we can draw some very good working hypotheses on how these proteins act together.”
The two proteins are like parts of a car that enable oil to reach the engine. In plants, the “oil” is calcium and chloride and the “fuel” is water and sunlight. The structure of PsbP and PsbQ facilitates the efficient use of calcium and chloride in a plant, enabling it to produce oxygen.
“Within the photosynthesis field, we’ve been thinking that these two proteins must be associated, but we didn’t have any direct evidence. Now, after 30 years of work, the student who is the first author on this paper has provided direct evidence that they are interacting,” Bricker said.
What is the significance of this research?
Bricker, the principle research investigator, said the problem of solving oxygen evolution in photosynthesis and determining how proteins work together has been one he has worked toward solving for 30 years. He stuck with this research so other scientists could understand how the proteins interact.
“Science almost never occurs in leaps and bounds,” Bricker said. “[Scientists] stand on the shoulders of giants and build forward. And often, our success comes from being in the right place at the right time because science doesn’t advance at a very rapid rate.”
Bricker said there have been lots of theories within the last 30 years that he has spent researching these proteins. Mummadisetti’s finding is important because it gives direct evidence that the two protein components interact in food and oxygen production in plants.
Mummadisetti said she sacrificed a lot of free time for research and teaching.
“There have been days I’ve been in the lab until midnight or later,” she said.
Her advice to students interested in pursuing research is be prepared for the dedication and the amount of time it requires. If they want results, she said, students have to be motivated.
The amount of work she put into the protein research earned Mummadisetti the title of principal author on the academic paper, published in Proceedings of the National Academy of Sciences journal in October.
Your future plans?
Mummadisetti said the support and recognition she received isn’t only on a national level.
Lots of professors have congratulated her, and she even received a Ron and Mary Neal Professors Used as Fellowships fellowship, which is given to two biological sciences students each year.
Mummadisetti said the requirements for the fellowship include outreach, teaching ability, academics and extracurricular activities.
“I think this paper had a major role in me receiving it, though,” she said.
For Mummadisetti, who came from India in 2008 to attend college, it is just the beginning. She said only half of the photosynthesis project is complete, and a post-doctorate and job hunt still lie ahead of her.
“It’s not over,” Mummadisetti said with a chuckle. “I’m just warming up.”