Development and Utilization of the DsRed2 Visual Reporter Gene System Driven by Soybean GmUbi Promoter
This study demonstrates that the soybean endogenous GmUbi promoter effectively drives the DsRed2 visual reporter gene to enable simple, rapid, and non-destructive screening of transgenic events in both Arabidopsis and soybean, exhibiting significantly higher activity than the CaMV 35S promoter.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
In the world of plant science, researchers often need to know if a specific piece of DNA has successfully entered a plant cell and is doing its job. To find out, they use "reporter genes," which act like tiny, built-in signal lights. For decades, scientists have relied on methods that require killing the plant or adding special chemicals to make the signal appear, much like developing a photograph in a darkroom. These methods are useful but destructive; once the test is done, the plant is damaged or dead, and the process cannot be repeated on the same living specimen. More recently, scientists have turned to fluorescent proteins, which glow in the dark when hit with the right color of light. Among these, red fluorescent proteins are particularly valuable because plants naturally glow in blue and green, making the red signal stand out clearly without interference. However, for this red glow to be useful as a simple screening tool, it must be bright enough to be seen without expensive microscopes, and the "switch" that turns the gene on—the promoter—must be powerful enough to drive the signal in every part of the plant.
A team of researchers at Liaocheng University in China set out to build a better version of this visual tool for soybeans and their close relative, the model plant Arabidopsis. They focused on a specific gene that produces a red fluorescent protein called DsRed2. The critical question was not just whether the protein glows, but which genetic "switch" could make it glow brightly enough to be seen with the naked eye. They compared the standard switch used in most labs, known as the 35S promoter, against a switch found naturally within the soybean itself, called the GmUbi promoter. The goal was to see if the soybean's own switch could drive the red light more effectively than the foreign one, creating a system where a scientist could simply look at a plant and instantly know if it had been genetically modified.
To test this, the researchers first created two different genetic packages. One package used the standard 35S switch to turn on the red light gene, and the other used the soybean GmUbi switch. They introduced these packages into soybean roots using a soil bacterium that naturally transfers DNA into plants. After two weeks, the difference was stark. The roots carrying the soybean switch glowed with a deep, visible red color that could be seen even in normal daylight. In contrast, the roots with the standard 35S switch appeared white to the naked eye, requiring a special light source to reveal a faint glow. When the team measured the brightness of the light, the roots with the soybean switch were more than twice as bright as those with the standard switch. As time passed, the red color in the soybean-switched roots only grew deeper and more intense, showing that the protein was continuously building up inside the plant cells.
Encouraged by these results, the team moved on to growing whole plants. They transformed both Arabidopsis and soybean plants using the soybean switch. In the Arabidopsis plants, the red signal appeared in the seed pods and the seeds themselves. When the seeds were mature, they could be sorted by eye: the genetically modified seeds had a distinct red tint, while the non-modified seeds remained their natural yellow-green color. This red color was not just a surface stain; it was visible inside the seed as well. When these red seeds were planted, the resulting seedlings showed red stems and leaves, allowing researchers to identify the successful plants immediately after they sprouted, without needing to cut them open or use any instruments.
The results were even more striking in the soybean plants. The flowers of the modified soybeans turned a pale red, a color that stood out clearly against the white flowers of normal soybeans. As the plants grew, the red pigment accumulated in the pods and the seed coats. When the seeds were harvested, many of them displayed a bright, vivid red color. The researchers noted that while young leaves remained green, older leaves on the modified plants eventually turned brown, a natural aging process that coincided with the accumulation of the red protein. Crucially, when these red seeds were planted, the new seedlings showed red cotyledons and stems right from the start. This meant that a farmer or researcher could walk through a field or a greenhouse and pick out the genetically modified plants simply by looking for the red color, a task that previously required complex molecular testing.
The study confirms that the soybean's own GmUbi promoter is a far more powerful driver for this red fluorescent protein than the standard switch used in laboratories. This discovery offers a simple, non-destructive way to screen for successful genetic changes in plants. Instead of waiting for chemical reactions or using expensive equipment, scientists can now rely on a natural color change that becomes more obvious as the plant grows. Because the red protein gene is short and compact, it is also easier to fit into genetic engineering tools compared to other colorful markers that require multiple large genes. This approach provides a reliable, visual method to track genetic modifications from the moment a seed germinates through to the mature plant, streamlining the process of developing new crop varieties.
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