Today we are going to take a break from the usual human health related topics to stop and smell the roses ... petunias. Specifically some petunias that were made in the lab and transgenically modified to express a green fluorescent protein. The data for the generation of these flowers was recently published in Nature Scientific Reports in an article titled "Generation of brilliant green fluorescent petunia plants by using a new and potent fluorescent protein transgene." I present this article to you partly because the science is neat to talk about, but mostly because glowing things are cool. Who doesn't enjoy glowing fish, mouse, cat or wedding dress? So with out further adieu let us begin!

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_{Fluorescent Petunia Image Reproduced from [1]}

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Transgenics

Fluorescent proteins are very widely used tools in biochemical/biological research. Most especially cell biology/microscopy. Where the expression of proteins with a fluorescent protein fused, allows scientists to visualize just where in a cell the protein of interest actually resides. That is a fact that perhaps you did not know, the proteins expressed in a cell are NOT just uniformly distributed throughout the cytosol, but rather congregate oftentimes at points of interest (like on specific regions of DNA, or in specific locations of the cell membrane).

Plants themselves pose unique challenges in these fluorescence labeling strategies as they contain many native compounds which have their own fluorescence spectrum (you might not know it, but chlorophyll can glow when the right light is shined upon it) and under the right conditions can complicate analysis. Beyond this, until relatively recently making an entirely fluorescent plant was limited to only two varieties of plants, Arabidopsis thaliana and tobacco which created a bit of controversy upon their creation. To get around some of the challenges researchers employed the use of a fluorescent protein (CpYGFP) from the organism Chiridius poppei which has an excitation spectrum which differs from the natural compounds found in plants (508 nm) and fluoresces green.

The problem with fluorescent proteins such as this is they require a very specific wavelength of light for emission and often some sort of filter to be able to seen. If your goal is to make some sort of decorative glowing plant, these specific light requirements as well as the need for filters for visualization prove to be a problem. Really, who wants to go through all of that work? So, to make things less complicated, the authors of the study we discuss today sought out a fluorescent protein which could be used to enable a plant to be excited by some sort of invisible light (like a UV lamp/black light).

To accomplish this the researchers turned to a different fluorescent protein called eYGFPuv, which has a strong absorbance spectrum maxima in the UV range (398 nm light) and a bright green fluorescence as well. They compared the excitation and emission spectrum of this UV excitable fluorescent protein against the traditional green fluorescent protein (image to the left) and show that the light they emit (dashed lines) is highly similar. This protein would enable exactly the situation we described above, use of a 'black light' to result in a whole plant that glows bright green.

Makin' Them Petunias

To get the fluorescent protein into the genome of the petunia, the researchers turned to using a DNA casette of three copies of the fluorescent protein's gene and the 35S promoter sequence from the cauliflower mosaic virus or CaMV and the transcriptional terminator from Arabidopsis thaliana's heat shock protein 18.2 inorder to insert the fluorescent gene into the petunia genome. [4] Which likely sounds like a bunch of science mumbo jumbo, but basically it boils down to the researchers used specific sequences of DNA that would enable the fluorescent protein gene to fuse into the plant's DNA. Thus as the plant grows, it will be expressing the fluorescent protein as if it were one of its own.

The authors proceeded to make a whole bunch of plant lines through this method and begun screening for plants that were fluorescent under UV light (they used 365 nM light). In the image to the right we can see the plants under normal lighting, and in the dark under the black light. The plant labeled WT is just a normal plant, there we see under the black light no glowing. But for the transgenic plants we see glowing in two of the lines they show here, plant line p701 and p705. In both cases it seems like the entire plant is expressing the fluorescent protein.

They weren't just looking for fluorescent leaves however, they wanted some glowing petunia flowers, largely for looking at because they look damn cool. Which is precisely what we are looking at below, they allowed some successfully glowing plants from the above experiments continue to grow and to flower.

_{Reproduced From [1] Figure 2A}

Then again examined them under the dark/black light conditions and we can see that they successfully generated a variety of plant lines with flowers that are in-fact able to glow green. We can place a special emphasis on their plant line P705 which looks, at least to my eyes to glow brighter than the other specimens they are showing here.

Concluding Remarks

The authors of this article were successful in generating an ornamental petunia which is able to glow bright green under a black light. What do you think about this? Is a glowing plant cool? Would you want to buy something like this? One could make a really weird looking nighttime flower garden with these, that's for sure!

Sources

Image Sources

1. Linked Image 1
2. Linked Image 2
3. Linked Image 3
4. Linked Image 4
5. Linked Image 5

Text Sources

1. https://www.nature.com/articles/s41598-018-34837-2.pdf
2. https://www.sciencedirect.com/science/article/pii/S037811190500733X
3. https://www.ncbi.nlm.nih.gov/pubmed/28700734
4. https://www.sciencedirect.com/topics/medicine-and-dentistry/cauliflower-mosaic-virus