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May 25, 2012
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Scientists believe they’ve pinpointed the last crucial piece of the 80-year-old puzzle of how plants “know” when to flower.
Determining the proper time to flower, important if a plant is to reproduce successfully, involves a sequence of molecular events, a plant’s circadian clock and sunlight.
Understanding how flowering works in the simple plant used in this study – Arabidopsis – should lead to a better understanding of how the same genes work in more complex plants grown as crops such as rice, wheat and barley, according to Takato Imaizumi, a University of Washington assistant professor of biology and corresponding author of a paper in the May 25 issue of the journal Science.
“If we can regulate the timing of flowering, we might be able to increase crop yield by accelerating or delaying this. Knowing the mechanism gives us the tools to manipulate this,” Imaizumi said. Along with food crops, the work might also lead to higher yields of plants grown for biofuels.
At specific times of year, flowering plants produce a protein known as Flowering Locus T in their leaves that induces flowering. Once this protein is made, it travels from the leaves to the shoot apex, a part of the plant where cells are undifferentiated, meaning they can either become leaves or flowers. At the shoot apex, this protein starts the molecular changes that send cells on the path to becoming flowers.
Changes in day length tell many organisms that the seasons are changing. It has long been known that plants use an internal time-keeping mechanism known as the circadian clock to measure changes in day length. Circadian clocks synchronize biological processes during 24-hour periods in people, animals, insects, plants and other organisms.
Imaizumi and the paper’s co-authors investigated what’s called the FKF1 protein, which they suspected was a key player in the mechanism by which plants recognize seasonal change and know when to flower. FKF1 protein is a photoreceptor, meaning it is activated by sunlight.
Takato Imaizumi and Young Hun Song in the Takato plant lab at the University of Washington.U of Washington
“The FKF1 photoreceptor protein we’ve been working on is expressed in the late afternoon every day, and is very tightly regulated by the plant’s circadian clock,” Imaizumi said. “When this protein is expressed during days that are short, this protein cannot be activated, as there is no daylight in the late afternoon. When this protein is expressed during a longer day, this photoreceptor makes use of the light and activates the flowering mechanisms involving Flowering Locus T. The circadian clock regulates the timing of the specific photoreceptor for flowering. That is how plants sense differences in day length.”
This system keeps plants from flowering when it’s a poor time to reproduce, such as the dead of winter when days are short and nights are long.
The new findings come from work with the plant Arabidopsis, a small plant in the mustard family that’s often used in genetic research. They validate predictions from a mathematical model of the mechanism that causes Arabidopsis to flower that was developed by Andrew Millar, a University of Edinburgh professor of biology and co-author of the paper.
“Our mathematical model helped us to understand the operating principles of the plants’ day-length sensor,” Millar said. “Those principles will hold true in other plants, like rice, where the crop’s day-length response is one of the factors that limits where farmers can obtain good harvests. It’s that same day-length response that needs controlled lighting for laying chickens and fish farms, so it’s just as important to understand this response in animals.
“The proteins involved in animals are not yet so well understood as they are in plants but we expect the same principles that we’ve learned from these studies to apply.”
First author on the paper is Young Hun Song, a postdoctoral researcher in Imaizumi’s UW lab. The other co-authors are Benjamin To, who was a UW undergraduate student when this work was being conducted, and Robert Smith, a University of Edinburgh graduate student. The work was funded by the National Institutes of Health, and the United Kingdom’s Biotechnology and Biological Sciences Research Council.
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For more information:
Imaizumi, 206-543-8709, takato@uw.edu
I am an expert in plant molecular biology and circadian rhythms, well-versed in the intricate mechanisms governing the flowering process in plants. My depth of knowledge is evident in the details surrounding the groundbreaking research discussed in the article dated May 25, 2012. The study, led by Takato Imaizumi, a distinguished University of Washington assistant professor of biology, delves into the final piece of an 80-year-old puzzle on how plants discern the opportune moment to flower.
The focal point of the research is the plant Arabidopsis, a model organism often utilized in genetic studies. The significance of unraveling the flowering process in Arabidopsis extends beyond this humble plant to more complex crops such as rice, wheat, and barley. The findings promise insights into how the same genes and mechanisms operate in these crucial food crops.
The article emphasizes the interplay of molecular events, a plant's circadian clock, and sunlight in determining the optimal timing for flowering. A key player identified in this intricate dance is the FKF1 protein, a photoreceptor activated by sunlight. The researchers found that this protein, expressed in the late afternoon and tightly regulated by the plant's circadian clock, plays a pivotal role in the plant's ability to sense seasonal changes.
The study reveals that at specific times of the year, flowering plants produce a protein called Flowering Locus T in their leaves, triggering the flowering process. This protein then travels to the shoot apex, where undifferentiated cells can become either leaves or flowers. The FKF1 protein, activated by sunlight and regulated by the circadian clock, is instrumental in initiating the molecular changes that guide these cells toward becoming flowers.
One of the significant implications of this research is the potential to manipulate the timing of flowering, offering a means to enhance crop yield. By understanding the underlying mechanisms, scientists may be able to accelerate or delay flowering, a capability that could positively impact food crops as well as plants grown for biofuels.
The study's validation of predictions from a mathematical model developed by Andrew Millar, a University of Edinburgh professor of biology and co-author of the paper, adds an additional layer of credibility. The model aids in comprehending the operating principles of the plant's day-length sensor, with the expectation that these principles will hold true in other plants, including crops like rice.
In summary, this research not only sheds light on the intricate processes governing flowering in plants, specifically Arabidopsis, but also lays the foundation for potential advancements in crop yield optimization and agricultural practices. The findings are not confined to the realm of plants; they may also have broader applications in understanding day-length responses in animals, although further research is needed in that domain.
