For
decades, scientists have been stumped by the signals plants send
themselves to initiate photosynthesis, the process of turning sunlight
into sugars. The researchers have now decoded those previously opaque
signals.
For half a century, botanists have known that the command center of a
plant cell, the nucleus, sends instructions to other parts of the cell,
compelling them to move forward with photosynthesis. These instructions
come in the form of proteins, and without them, plants won’t turn green
or grow.
“Our challenge was that the nucleus encodes hundreds of proteins
containing building blocks for the smaller organelles. Determining which
ones are the signal to them to trigger photosynthesis was like finding
needles in a haystack,” said the senior author.
The process the scientists in the laboratory used to find four of these proteins is now documented in a Nature Communications paper.
Previously, the team demonstrated that
certain proteins in plant nuclei are activated by light, kicking off
photosynthesis. These four newly identified proteins are part of that
reaction, sending a signal that transforms small organs into
chloroplasts, which generate growth-fueling sugars.
The senior author compares the whole photosynthesis process to a symphony.
“The conductors of the symphony are proteins in the nucleus called
photoreceptors that respond to light. We showed in this paper that both
red and blue light-sensitive photoreceptors initiate the symphony. They
activate genes that encode the building blocks of photosynthesis.”
The unique situation, in this case, is that the symphony is performed in
two “rooms” in the cell, by both local (nucleus) and remote musicians.
As such, the conductors (photoreceptors), who are present only in the
nucleus, must send the remotely located musicians some messages over
distance. This last step is controlled by the four newly discovered
proteins that travel from the nucleus to the chloroplasts.
This work was funded by the National Institutes of Health, in the hopes
that it will help with a cure for cancer. This hope is based on
similarities between chloroplasts in plant cells and mitochondria in
human cells. Both organelles generate fuel for growth, and both harbor
genetic material.
Currently, a lot of research describes communication from organelles
back to the nucleus. If something is wrong with the organelles, they’ll
send signals to the nucleus “headquarters.” Much less is known about the
activity-regulating signals sent from the nucleus to the organelles.
“The nucleus may control the expression of mitochondrial and chloroplast
genes in a similar fashion,” said the author. “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,” the author said.
The significance of understanding how photosynthesis is controlled has
applications beyond disease research. Human settlements on another
planet would likely require indoor farming and creating a light scheme
to increase yields in that environment. Even more immediately, climate
change is posing challenges for crop growers on this planet.
“The reason we can survive on this planet is because organisms like
plants can do photosynthesis. Without them there are no animals,
including humans,” the author said. “A full understanding of and ability
to manipulate plant growth is vital for food security.”
https://www.nature.com/articles/s41467-022-35080-0
http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Fanterograde-signaling&filter=22