Did you know that plants work like incredibly smart factories? Every leaf that unfolds and every root that grows follows detailed instructions contained within the plant's cells.
Professor Qi Linlin from the Faculty of Synthetic Biology at Shenzhen University of Advanced Technology (SUAT), working with the Jiří Friml group at the Institute of Science and Technology Austria (ISTA), recently published a breakthrough study in the journal Nature titled “TIR1-produced cAMP as a second messenger in transcriptional auxin signalling.”
Their discovery challenges long-held beliefs by demonstrating that plant cells not only rely on the well-known growth hormone auxin (the “commander”) to send signals, but also on a vital "messenger" molecule called cyclic adenosine monophosphate, or cAMP.
To understand this, imagine a busy city's traffic system. Auxin is like a traffic controller who directs the flow when holding a special pass. When auxin arrives, it opens certain pathways for signals to move through the plant cell.
For nearly 20 years, scientists believed that auxin's effects depended on a single mechanism — binding to a receptor called TIR1/AFB, which marks a protein called Aux/IAA for destruction. Getting rid of Aux/IAA “releases the brakes” on specific genes, allowing them to turn on and guide growth.
However, this new research reveals that there's another “secret tunnel” — the cAMP signaling pathway. Even when the usual traffic lights (Aux/IAA proteins) are working normally, this new pathway can send signals forward without waiting for those lights to change.
Professor Qi explains, “The classic model says that removing Aux/IAA proteins is absolutely necessary and enough for auxin to trigger gene activity — like releasing a brake pedal starts the engine. However, our findings reveal that removing these brakes is neither always required nor sufficient to switch on the genes. Instead, the enzyme activity of TIR1 that makes cAMP is essential for sending the auxin signal. For the first time, we've proven that cAMP acts as a ‘second messenger’ inside plant cells.”
Back in 2022, during his postdoctoral work in the Friml group, Qi was the first to show that TIR1/AFB receptors can produce cAMP by converting ATP, influencing root growth and how roots respond to gravity. However, the connection between this enzyme activity and the known protein degradation pathway wasn't clear, and it hadn't been confirmed whether cAMP really acts as a messenger in these processes.
This latest study changes how we understand plant growth signals. It proves that cAMP is a vital second messenger inside plant cells and opens new avenues for research.