What is potato tuberization and why is it important?

The process of potato tuberization is the formation of tubers, the edible part of the potato plant, which is essential for crop yields and food security. Scientists have long sought to understand how it is controlled, and this knowledge is crucial for improving potato production globally. Understanding tuberization helps optimize conditions for the potato plant to produce the tubers.

What role does StCOL1 play in potato tuberization?

StCOL1 is a protein that, according to a long-held theory, is crucial for tuberization. It is produced during short nights, and light from a night break (a flash of light during a long night) was thought to destabilize it. When StCOL1 is present during a night break, it was thought to trigger StSP5G production, which then suppresses StSP6A, a key signal for tuber formation. Recent research suggests the process is much more complicated than initially thought. It is central to the understanding of how the potato plant forms tubers.

What are StSP5G and StSP6A, and how do they relate to tuberization?

StSP5G and StSP6A are genes involved in the tuberization process. StSP5G is believed to be produced due to StCOL1, and it suppresses StSP6A, which is a key signal for tuber formation. Research shows that StCOL1, StSP5G, and StSP6A do not follow a simple relationship and that the understanding of their interplay is key to understanding tuberization. The expression of these genes is a key factor in determining whether a potato plant forms tubers.

How does a night break influence potato tuberization?

A night break is a flash of light during a long night, specifically used to halt tuberization. Scientists had believed that the application of a night break would halt tuberization. The new study shows that the timing of the night break is important and the effectiveness of the break depends on when it is applied during the dark period. A night break applied when StCOL1 expression was at its peak did not effectively delay tuberization, suggesting that StCOL1 and light are not the only elements at play.

What is the 'StCOL1-light coincidence model' and what does the recent research say about it?

Scientists have traditionally believed that light and the presence of StCOL1 were the key determinants of tuberization. This 'coincidence model' suggested that when StCOL1 expression coincided with light exposure, it would trigger a cascade of events, ultimately suppressing tuber formation. However, recent studies show this model isn't comprehensive, suggesting that factors other than StCOL1, StSP5G, and StSP6A influence tuber formation. The new study indicates that the regulation of tuberization is more complex, and while StCOL1 plays a role, it is not the sole factor determining whether a potato plant forms tubers. The study highlights the need to look beyond the StCOL1-light coincidence model and explore additional layers of control that influence tuberization.

Potato plant with glowing roots, partially illuminated, symbolizing the tuberization mystery.

Potato Tuberization Mystery: Why Light Isn't Always the Answer

Nico Varela in Science & Nature December 2025 • 4 min read.

"New research challenges the long-held belief that light alone controls tuber formation in potatoes, revealing a complex interplay of factors."

The humble potato, Solanum tuberosum, is a global staple, feeding millions worldwide. Understanding how potatoes form tubers – the part we eat – is crucial for optimizing crop yields and ensuring food security. For a long time, scientists believed that day length, specifically short days (long nights), was the primary trigger for tuberization. The application of a night break (a flash of light during a long night) would halt tuberization, but the exact mechanism behind this repression remained elusive.

Researchers have been exploring a model similar to that of photoperiodic flowering in Arabidopsis, suggesting that a protein called StCOL1, produced during short nights, is stabilized by light from a night break. This stabilization was thought to trigger the production of StSP5G, which in turn suppresses StSP6A, a key signal for tuber formation. However, recent research is beginning to show that this model is not as simple as once believed.

A new study digs deeper into this 'coincidence model,' questioning whether the timing of StCOL1 expression and light exposure is the definitive answer to night-break repression of tuberization. By carefully manipulating light exposure and monitoring the expression of key genes, scientists are uncovering a more nuanced understanding of potato tuberization.

The Night Break Paradox: When Light Doesn't Repress Tuberization

Potato plant with glowing roots, partially illuminated, symbolizing the tuberization mystery.

The study explored how night breaks at different times affect tuberization. Researchers grew Solanum andigena plants (a short-day potato variety) under short-day conditions, applying night breaks at various points in the dark period. They then monitored the presence of the StCOL1 protein, the expression levels of StCOL1 itself, and the expression of its downstream targets, StSP5G and StSP6A.

The team's findings challenged the prevailing theory. They discovered that a night break applied when StCOL1 expression was at its peak did not effectively delay tuberization. Conversely, tuberization was significantly repressed when the night break coincided with low or no StCOL1 expression. This implies that the simple 'coincidence' of StCOL1 expression and light cannot fully explain the night-break phenomenon.

Timing Matters: A night break's effectiveness hinges on when it's applied during the dark period, not just whether it occurs.
StCOL1 Isn't Everything: Stable StCOL1 levels didn't always lead to StSP5G production, and increased StSP5G didn't guarantee StSP6A repression.
Unknown Factors at Play: The study hints at a yet-to-be-identified level of control between StCOL1, StSP5G, and StSP6A, which ultimately dictates whether a potato plant forms tubers.

These results suggest that the regulation of tuberization is more intricate than previously thought. While StCOL1 undoubtedly plays a role, other factors influence StSP5G and StSP6A expression, ultimately determining tuber formation. It's not simply about StCOL1 presence or absence; it's about a complex interplay of signals.

Unraveling the Mystery: The Future of Potato Research

This research throws a wrench in the traditional understanding of potato tuberization, highlighting the need to look beyond the StCOL1-light coincidence model. The existence of an additional control layer opens exciting new avenues for investigation.

Future research should focus on identifying the unknown factors regulating StSP5G and StSP6A expression. Understanding how these factors interact with StCOL1 could unlock more effective strategies for manipulating tuber formation in potatoes.

Ultimately, a deeper understanding of potato tuberization can lead to improved crop management practices, enhanced yields, and a more sustainable food supply. Cracking the code of tuber formation could revolutionize potato farming and contribute to global food security.