Will a better understanding of the process of photosynthesis help to grow plants under artificial lighting?
The intensity of sunlight is constantly changing, and the photosynthetic mechanism - the process that plants, algae and certain types of bacteria use to convert solar energy into chemical energy - must adapt to the changing conditions to ensure optimal utilization of the radiation. Similar to the pupillary reflex - which causes them to expand or contract depending on the lighting - organelles in plant cells also change in response to light. But unlike us, plants cannot look away or rest in the shade, and they have to be able to deal with different intensities of radiation, as well as the absence of sunlight during the hours of darkness.
Without the photosynthetic mechanism, life on Earth, as we know it, would not be possible. This process is not only responsible for the production of most of the oxygen in the Earth's atmosphere, it is also the one that ensures the availability of food in our world, fixes atmospheric carbon dioxide and moderates climate change processes. Therefore, a good understanding of the processes of photosynthesis is essential for humanity in dealing with the future climate challenges. Although the process has been thoroughly studied for many years, we still do not fully understand it. in the laboratory of Prof. Ziv Rich In the Department of Biomolecular Sciences at the Weizmann Institute of Science, we aim to add another layer to the understanding of this process. This understanding will allow in the future to optimize the utilization of photosynthesis for human needs, or to develop artificial mechanisms that mimic the natural process.
The utilization of the sun's energy in photosynthesis is done through the transfer of electrons between proteins in an organelle called a chloroplast. In this organ there is a complex system of membranes, some with a dense structure, and some with a more spacious arrangement, and until now researchers believed that the spatial structure of the system forces the electrons to travel a large distance between the proteins, thus slowing down the process. in the article published in the journal Nature Plants, scientists led by Dr. Rinat Nebo, a faculty scientist in Prof. Reich's group, showed that in the transition from darkness to light, the membranes change their spatial structure in a way that allows greater physical proximity between the proteins, thereby shortening the distance that the electrons have to travel.
On the way to discovering the surprising change in the arrangement of the membranes, the researchers used a scanning electron microscope to examine the chloroplast membranes under dark and light conditions, and compared the arrangement of the proteins on the membranes. "When we looked at the density of the proteins, we realized that it is not the proteins themselves that change their location - as we thought until now - but that the change is made in the way the membranes are organized in space," explains Dr. Nebo. Another test - this time with a penetrating electron microscope - confirmed the hypothesis of Dr. Nevo and her colleagues, and showed that the membranes reorganize and thus cause the proteins to come closer to each other. Apparently one of the reasons why the near state is not permanent, and the membranes move apart again in dark conditions, is the protection of the proteins through their isolation in weak light conditions, when the photosynthetic activity taking place is minimal.
Unlike us, plants cannot look away or rest in the shade, and they have to be able to cope with different intensities of radiation, as well as the absence of sunlight during the hours of darkness
After the scientists discovered how the membranes rearrange themselves according to the lighting conditions, they performed experiments on two groups of genetically modified plants: one in which the spatial structure of the membranes is "locked" in a state of light and active photosynthesis, and a second group in which the structure remains in a state of darkness and prevents the membranes from coming closer together. The scientists showed that the plants in the first group were larger and carried out more photosynthesis compared to their friends in the "dark group".
In the future, Dr. Nevo and her colleagues plan to examine whether the use of transgenic plants in which the spatial arrangement of the membranes can be controlled will help grow plants in relatively weak light, which will make it possible to save energy when growing plants in artificial lighting - a possibility that may be a necessity in the era of climate change.
The article was dedicated to the memory of Dr. Eyal Shimoni, a faculty scientist from the chemical research infrastructure unit at the institute, who helped implement the electron microscopy in the research, until he passed away prematurely in 2023.
Dr. Yuval Gerti and Yuval Bossi from Prof. Reich's group, Dr. Smeder Zeidman from the Department of Chemical Research Infrastructures at the Institute, Prof. Helmut Kirchhoff from Washington State University and Dr. Dana Harubi from the Volcanic Institute also participated in the study.
