New Study Shines Light on Photosynthesis Process

New Study Shines Light on Photosynthesis Process
Plant cells with visible chloroplasts (from a moss, Plagiomnium affine) Credit: Wikipedia

A photosynthesis is an essential process for humans and plants as well. The photosynthesis process is used by plants and other organisms to convert light energy into chemical energy. It produces the oxygen we breathe and much of the food we consume by using sunlight. But there is a problem within the process. One of the vital players in this process, a protein complex called Photosystem II, essentially paralyzes itself by producing harmful chemicals known as reactive oxygen species.

Since from many years, this problem was puzzling researchers. To sort out this issue, scientists from the Louisiana State University (LSU) come together with scientists from Palacký University, Czech and the University of Cincinnati in Ohio. They have solved a longstanding mystery in the photosynthesis process.

Professor Terry Bricker said, “Photosystem II is part of the electron transport system that makes the oxygen in plants. It gets the ‘show on the road’ so to speak. But it has a problem. Because of the chemistry that this protein complex performs in making oxygen gas, it generates reactive oxygen species, such as hydrogen peroxide, that are damaging to proteins. While Photosystem II produces oxygen, it’s also damaging itself in the photosynthesis process.”

“This causes 20% reduction in the productivity in Photosystem II over the course of a few hours of photosynthetic activity during daylight hours for plants. Thus, it causes several economic impacts for society. For example, producing plant-based food and other products.”

“The damage to Photosystem II need to fix to keep the photosynthesis show on the road. Just as a mechanic would have to fix a broken piston in your car’s engine to get you back on the road,” he added.

For the first time the specific regions of damage that prompt repair of Photosystem II. To do this, scientists primarily focused on understanding the damage process that affects Photosystem II, or how the damage occurs. They started finding for which reactive oxygen species are involved and where exactly they are damaging this protein complex.

They found that a hydroxyl radical and a superoxide are responsible for damaging Photosystem II during photosynthesis. In addition, they discovered the specific regions of the Photosystem II protein complex where these reactive oxygen species wreak havoc. For that purpose, they used a technique called mass spectrometry. Through this technique, they were able to find out mass spectrometry.

Bricker said, “We determined which amino acid residues, portions of the individual proteins making up Photosystem II. They actually change with the reactive oxygen species produced during photosynthesis. The regions D1 and D2 of Photosystem II closest to where the reactive oxygen species are created during photosynthesis are damaged first.”

By using spinach leaves and making them exposed to sunlight, scientists were able to address the areas in Photosystem II.

Co-author Ravindra Kale said, “For many years, scientists have tried to search for insights on the process that impairs Photosystem II. In this study, we’ve identified the reactive oxygen species mainly responsible for the photooxidative damage and their primary targets and mechanism. This opens a new paradigm for understanding the systematic behavior of the Photosystem II, which produces oxygen during photosynthesis.”