Molecular mechanism by which StSN2 overexpression inhibits the enzymatic browning of potato

by Jorge Luis Alonso with ChatGPT-4

A new study published in Plant Communications reveals a previously unobserved tuber-inducing activity of the StSP3D and StFTL1 proteins, in addition to their known florigenic activity. This research offers new perspectives on photoperiodic tuberization in potato. Below is a summary of the study.

To make the research summaries more accessible and practical, I have now added a simplified version that is written with clarity suitable for an audience as young as 11. This supplement provides a straightforward explanation of the complex issues covered in the research. You can find it at the bottom of the page.

In the struggle against harsh climatic extremes, the potato, a beacon of geophytic species, creates a way to survive. It ingeniously innovates an auxiliary reproductive strategy by producing tubers, starch-filled vegetative storage organs that rise to global prominence as a staple food. Constantly pushing its limits, it evolves to adapt to long-day (LD) tuberization from its short-day (SD)-dependent ancestor, S. tuberosum group Andigena.

As vigilant sentinels, potato leaves sense day length and initiate the production of a mobile signal. This signal then travels either to the apex of the shoot or to underground stolons. This action, in turn, triggers flowering or tuber formation. The recent elucidation of StSP6A’s role in storage organ formation has sparked a flurry of research in this exciting field.

This study contributes to this dynamic field of research by demonstrating that overexpression of the SD-activated genes StSP3D and StFTL1 induces tuberization independent of photoperiod. Interestingly, this effect is transmitted through the grafts, positioning StSP3D and StFTL1 as long-distance tuber-inducing signals.

In a previous study of StSP3D, it was found that when this gene was silenced, plants sprouted tubers at the same rate as their wild-type counterparts under SD conditions. However, the same plants showed a striking delay in the transition to flowering under LD conditions. Interestingly, the transcripts of StSP3D, StFTL1, and StSP6A all come to life in leaves under SD conditions. However, it is noteworthy that the activation of StSP3D is one notch lower than its counterparts. This finding suggests a possible overlap in the roles of these genes in tuber induction under SD conditions.

S. etuberosum, a wild relative of the potato, interestingly harbors a naturally inactivated SeSP6A. However, even when used as a scion donor, it successfully induces tuber formation in potato rootstocks under LD conditions. To further investigate this phenomenon, the team uses the precision gene-editing tool CRISPR/Cas9 to create SP3D mutations. In doing so, they unmask SP3D as a stand-alone tuber-inducing signal that functions without leaf SP6A expression. Based on this revealing discovery, they theorize that all SD-activated FT-like genes may support SD-responsive tuberization, thereby facilitating potato adaptation to different latitudes.

Furthermore, by overexpressing either StSP3D, StSP6A, or StFTL1, they induced tuber formation under non-inductive LD conditions. However, mutation of SeSP3D in S. etuberosum (with SP6A deactivated) does not completely stop tuberization of S. etuberosum/E109 grafts under LD conditions. These intriguing results suggest that StSP3D, StSP6A, or StFTL1 may enhance StSP6A expression in stolons and participate in a positive feedback loop to increase StSP6A expression.

Members of the PEBP gene family, although undergoing a process of duplication and subfunctionalization, appear to orchestrate in harmony to modulate the induction of daylength-dependent flowering/tuberization. Finally, it is shown that these FT-like genes not only control flowering and tuber induction, but also oversee meristem termination. This important discovery puts them in the spotlight as prime candidates for advancing potato genetics.

Source: Li, L., Mu, Y., Chen, J., Wang, Q., Lu, Y., Xin, S., Yang, S., Huang, X., Wang, X., & Lu, L. (2023). Molecular mechanism by which StSN2 overexpression inhibits the enzymatic browning of potato. Postharvest Biology and Technology, 203, 112416. https://doi.org/10.1016/j.postharvbio.2023.112416

Simplified Version

Now, let’s simplify the complicated scientific concepts in the previous text to make them as understandable as possible for an 11-year-old.

Plants program their meristem-associated developmental switches for timely adaptation to a changing environment.

This means that plants have a way of changing their growth patterns based on what’s happening around them, just like how you’d change your clothes depending on the weather.

Potato (Solanum tuberosum L.) tubers differentiate from specialized belowground branches or stolons through radial expansion of their terminal ends.

Potatoes grow underground from special branches called stolons. These stolons swell at the ends and become potatoes.

During this process, the stolon apex and closest axillary buds enter a dormancy state that leads to tuber eyes, which are reactivated the following spring and generate a clonally identical plant.

While the potatoes are forming, the tip of the stolon and buds nearby go to sleep, and they form what we see as ‘eyes’ on a potato. These ‘eyes’ wake up the next spring, growing into a new potato plant that is identical to the original one.

The potato FLOWERING LOCUS T homolog SELF-PRUNING 6A (StSP6A) was previously identified as the major tuber-inducing signal that integrates day-length cues to control the storage switch.

There’s a special thing in potato plants called StSP6A. It’s like a plant alarm clock that helps potatoes decide when to start storing food (which is what a potato is — a storage unit for food) based on how long the days are.

However, whether some other long-range signals also act as tuber organogenesis stimuli remains unknown.

Scientists aren’t sure if there are other signals in the plant that tell it when to start making potatoes.

Here, we show that the florigen SELF PRUNING 3D (StSP3D) and FLOWERING LOCUS T-like 1 (StFTL1) genes are activated by short days, analogously to StSP6A.

The researchers found out that two other things in potato plants, called StSP3D and StFTL1, also act like alarm clocks when the days get shorter.

Overexpression of StSP3D or StFTL1 promotes tuber formation under non-inductive long days, and the tuber-inducing activity of these proteins is graft transmissible.

If there’s a lot of StSP3D or StFTL1, the potato plant might start making potatoes even when the days are long. And, interestingly, these signals can be passed to another plant through grafting, which is like a plant transplant.

Using the non-tuber-bearing wild species Solanum etuberosum, a natural SP6A null mutant, we show that leaf-expressed SP6A is dispensable for StSP3D long-range activity.

The researchers did an experiment with a wild potato plant that doesn’t make potatoes and found out that StSP3D can still work even if there’s no StSP6A in the leaves.

StSP3D and StFTL1 mediate secondary activation of StSP6A in stolon tips, leading to the amplification of this tuberigen signal.

StSP3D and StFTL1 can turn on StSP6A at the tip of the stolon, which makes the “let’s make potatoes” signal stronger.

StSP3D and StFTL1 were observed to bind the same protein partners as StSP6A, suggesting that they can also form transcriptionally active complexes.

StSP3D and StFTL1 work with the same proteins as StSP6A, just as you and a friend might both like to play with the same kind of toy. This means that they can also help make things happen in plant cells.

Together, our findings show that additional mobile tuber-inducing signals are regulated by the photoperiodic pathway.

Taken together, these researchers have found that there are more signals moving around in the plant that tell it to make potatoes, and these are affected by how long the days are.

So let’s put it all together:

This research is about how potato plants decide when to start making potatoes, which is a way of storing food. They have signals, like alarm clocks, that tell them when to start. This usually happens when the days get shorter. The researchers found two other signals, called StSP3D and StFTL1, that can do the same thing. These signals can be transferred to another plant by grafting, much like a plant transplant. They also found that StSP3D can work even when there’s no StSP6A in the leaves and that StSP3D and StFTL1 can make the “let’s make potatoes” signal even stronger. This research adds to our understanding of how plants adapt to their environment and control their growth..

For more research on potato storage, click here: https://bit.ly/3u8OCtU.

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