The secret language of photosynthesis against cancer.
Communications between plant cells could help treat cancer by exploiting the communication pathway that is used to start photosynthesis.
For decades, scientists have been perplexed by the signals plants send to start photosynthesis, the process of converting sunlight into organic matter – mainly carbohydrates (sugars). Researchers at the University of California Riverside have now decoded these hitherto difficult-to-understand signals.
For half a century, botanists have known that the command center of a plant cell, the nucleus, sends instructions to the other parts of the cell, forcing them to proceed with photosynthesis. These instructions come in the form of proteins, without which plants do not turn green and grow. “Our challenge was that the nucleus encodes hundreds of proteins that contain the building blocks for smaller organelles. Determining what the signals are to trigger photosynthesis was like finding needles in a haystack,” said UCR botany professor Meng Chen. The process scientists in Chen’s lab used to find four of these proteins is now documented in a Nature Communications article.
Previously, Chen’s team had shown that certain proteins in plant nuclei are activated by light, kicking off photosynthesis. The four newly identified proteins are part of this reaction, sending a signal that turns tiny organs into chloroplasts, which generate sugars that fuel growth. Chen likens the entire process of photosynthesis to a symphony. “The symphony conductors are proteins in the nucleus called photoreceptors that respond to light. In this work we have demonstrated that photoreceptors sensitive to red and blue light initiate the symphony. They activate the genes that encode the building blocks of photosynthesis.” The unique situation here is that the symphony is performed in two “rooms” of the cell, by local (core) and remote musicians. The conductors (photoreceptors), present only in the nucleus, must send some remote messages to the remote musicians. This last step is controlled by the four recently discovered proteins that travel from the nucleus to the chloroplasts.
The analogies with human cells
This work was funded by the National Institutes of Health in hopes it could help find a cure for cancer . This hope is based on the similarities between the chloroplasts of plant cells and the mitochondria of human cells. Both organelles generate fuel for growth and both house genetic material. Currently, much research describes the communication from organelles to the nucleus. If something is wrong with the organelles, they send signals to the “headquarters” of the nucleus. Much less is known about the activity-regulating signals sent from the nucleus to the organelles.
“The nucleus could control the expression of mitochondrial and chloroplast genes in a similar way,” Chen said. “Thus, the principles we learn from the nucleus-chloroplast communication pathway could further our understanding of how the nucleus regulates mitochondrial genes and their dysfunction in cancer,” Chen said. The importance of understanding how photosynthesis is controlled has applications beyond disease research. Human settlements on another planet would likely require indoor farming and the creation of a lighting scheme to increase yields in that environment. Even more immediately, climate change is posing challenges for farmers on planet earth. “The reason we can survive on this planet is that organisms like plants can photosynthesise. Without them there would be no animals, including humans,” Chen said. “Full understanding and the ability to manipulate plant growth is critical to food security.”
