Photosynthesis signaling within plant cells is fundamental to life. Find out how a new discovery explains what triggers the process, potentially boosting crop yields and even helping cure cancer.
I can still remember Mrs. Sauer writing the formula on the blackboard back in Grade Six. It went like this:
C02 + H2O + Light —> CH2O + O2
In plain language, green plants use carbon dioxide, water and light, to produce carbohydrates and oxygen. Many readers will recognize this familiar botanical process as photosynthesis.
Up until the 1600s, people thought plants grew by drawing mass out of the soil. Jan van Helmont tested this idea by measuring the mass of plants as they grew, along with the soil mass in which they were rooted.
People Thought Plants Grew by Drawing Mass from Soil
Van Helmont discovered the soil’s mass hardly changed at all, which led him to believe that plant growth must come from watering them. There’s some truth to that, but it’s not the whole story.
In 1774, Joseph Priestly conducted an experiment where he put a candle inside a sealed bell jar. The candle burned out long before it ran out of wax.
He then discovered that if he placed a mouse inside the container, it couldn’t breathe. However, a mouse was quite happy inside the container if he also put a plant inside it for a few days.
Plants Absorb Carbon Dioxide and Emit Oxygen
He realized that the candle must absorb gas from the air and that plants replaced it. Today, we’d say candles consume oxygen while plants emit it.
A few years later, Jan Ingenhousz learned that plants also needed sunlight to restore the atmosphere in Priestly’s experiment. Then in 1796, Jean Senebier confirmed that carbon dioxide, oxygen and light were all part of the process.
Finally, Nicolas-Theodore de Saussure demonstrated that plants grow by absorbing sunlight and uptaking carbon dioxide and water, releasing oxygen as a byproduct. This was the turning point in understanding how plants fuel their growth.
Uptake of Carbon Dioxide and Water, Releasing Oxygen
Scientists have improved our understanding of photosynthesis over time. For example, Charles Reid Barnes came up with the term photosynthesis and described the process in more detail in 1893.
For more than 20 years, Professor Meng Chan has been studying plant development and growth. At the University of California, Riverside, he’s currently researching photosynthesis and the ways plants respond to light and temperature change.
Photosynthesis signaling takes place at the cellular level. Scientists have known for some time that the cell nucleus triggers the process by sending proteins to other parts of the plant cell called organelles.
Cell Nucleus Triggers Photosynthesis by Sending Proteins
Botanists have struggled to understand this photosynthesis signaling process in detail. Professor Chen and his colleagues have now decrypted the protein code underlying these signals.
Last month, the team published a paper in the journal Nature Communications explaining their findings. This study builds on their previous discovery that light activates certain proteins in plant cell nuclei, activating photosynthesis signaling.
“Our challenge was that the nucleus encodes hundreds of proteins containing building blocks for the smaller organelles, Professor Chen explained. “Determining which ones are the signal to them to trigger photosynthesis was like finding needles in a haystack.”
Compares Photosynthesis Signaling to Symphony Orchestra
Professor Chen compares photosynthesis signaling to a symphony orchestra, saying, “The conductors of the symphony are proteins in the nucleus called photo-receptors that respond to light. We showed in this paper that both red and blue light-sensitive photo-receptors initiate the symphony. They activate genes that encode the building blocks of photosynthesis.”
This cellular orchestra has conductors and musicians. The conductors are the photo-receptors in the nucleus, while the musicians are organelles within the cell called chloroplasts.
The photo-receptors direct the chloroplasts using four proteins Professor Chen’s team has identified. Botanists call these kinds of proteins sigma factors, and the names for the four involved in photosynthesis signaling are SIG1, SIG3, SIG5, and SIG6.
May Boost Crop Yields and Improve Indoor Farming
A better grasp of photosynthesis signaling may help boost global crop yields. Applying how light triggers plant growth could also improve indoor farming techniques, potentially even in colonies on other planets in the distant future.
This discovery’s implications extend far beyond botany and agriculture. The National Institutes of Health funded Professor Chen’s research because it may help oncologists cure cancer.
Just as chloroplasts play a key role in fueling plant growth, human cells have growth-driving organelles called mitochondria. Part of what causes cancer cells is that faulty mitochondria can cause tumours to form in human or other animal cells.
May Help Oncologists Cure Cancer
“The nucleus may control the expression of mitochondrial and chloroplast genes in a similar fashion,” Professor Chen explained. “So, the principles we learn from the nucleus-to-chloroplast communication pathway might further our understanding of how the nucleus regulates mitochondrial genes, and their dysfunction in cancer.”
Our biosphere is a web of interrelated living things. Each species depends on all the others.
Greater Reciprocity Between Plant and Animal Kingdoms
We’ve understood how carbon dioxide and oxygen balance plant and animal life through photosynthesis for more than a century. Probing deeper into photosynthesis signaling may lead to even greater synergy between the plant and animal kingdoms.
Professor Chen concluded by saying, “The reason we can survive on this planet is because organisms like plants can do photosynthesis. Without them there are no animals, including humans. A full understanding of and ability to manipulate plant growth is vital for food security.”
We always have more to learn if we dare to know.
Decoding the secret language of photosynthesis
Anterograde signaling controls plastid transcription via sigma factors separately from nuclear photosynthesis genes
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Agricultural Diversity Under Threat Worldwide
Soil Biodiversity Now Tracked Globally