Unexpected protein interactions needed to build flowers Ars Technica

The pros and cons of overtime – taking on an additional job in addition to working full time – is hotly debated. But in biology, overtime is not uncommon, as individual proteins often perform multiple functions. For many years, scientists have known that an unusual floral organ (UFO) protein appears to do some extra lighting.

Based on the structure of the protein, its role in plants is thought to target proteins for destruction. But it also works with leaf protein (LFY) to help flower formation. A team of scientists from France has now shed light on how this protein performs two roles.

Flowers and UFOs

When it comes to flower formation, foliar protein (LFY) is a real factor. Flowers are built from parts called sepals, petals, stamens, and carpels, arranged in whorls. The LFY protein, acting alone or in combination with other proteins, is responsible for activating genes necessary for the formation of each of these parts. LFY combines with UFO to help form the petals and stamens.

According to the study Lead author, François Barcy of the CNRS and the University of Grenoble Alpes, said the reason it took more than 25 years to figure out the mechanism of UFO-LFY was because of the “misguided nature of the UFO protein.”

The foreign body belongs to a group of about 700 proteins characterized by a pattern of amino acids, called the F-box domain, that regulates the levels of other proteins. The foreign body marks other proteins for destruction, Barsi said: “It places a chemical tag on the protein chosen for degradation. Once the protein is tagged, [some] Cell machines, called [a] The proteasome, recognizes the tag and cuts the protein into hundreds of pieces.”

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So, you might expect that UFO also stands for LFY for Destruction. Normally, it should degrade the LFY protein as well. However, in the case of LFY, we found that the foreign body had a completely different function – that of binding to a region of DNA that could not be accessed by LFY alone.

When an LFY and a UFO meet, they stick DNA near genes that are necessary to form the petals and stamens.

Barsi and his team began their research four years ago by mass-producing the foreign body protein in insect cells. “It was quite a challenge, because the foreign body is one of the most difficult proteins to produce artificially,” Barsi said.

Wherever there are flowers

It turns out that the foreign body does not need to destroy other proteins to work with LFY. We then modified it by removing the F-box domain responsible for the degradation of partner proteins. To our surprise, we discovered that even though its putative main function had been removed, the protein still worked well with the LFY protein,” Barsi said. The experiment revealed that the UFO protein performs few other functions than targeting proteins for destruction.

This add-on appears to involve altering the DNA sequences that Levy latches on to. The researchers obtained a 3D structure of the interaction between LFY and UFO and the regions of DNA they bind to using electron microscopy. According to Parcy, when UFO and LFY work together, they are able to latch onto regions of DNA responsible for petal and stamen formation. None of these proteins can latch onto this DNA on their own.

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“This means that while each protein has the ability to weakly touch a region of DNA, when combined, it adds to its strength, triggering an interaction with a new DNA template,” he said.

The LFY-UFO association is present in all flowering plants. Also in rice, two proteins, LFY and UFO, stick together to enable them to bind new regions of DNA, resulting in the development of the part of the plant that bears its grains, called the panicle.

what are you doing here?

According to Parcy, we currently do not know why the UFO protein continues to possess an F-box domain, which plays no role in its interaction with LFY.

“If this domain was completely useless, evolution would have removed it. The fact that it is still there means that it has a role that remains to be discovered. Perhaps the UFO plays a role in breaking down other proteins. We don’t know yet. But what we can say for sure is That this function is not necessary for making petals and stamens.”

However, it is not the only mystery surrounding flowers. One of the big mysteries is what caused the origin of the flowers, especially given that the association between LFY and UFO seems to predate the first flower. Our study indicates that this sharing mechanism was already present in gymnosperms such as conifers as well as in ferns. “She must have had another role when there were no flowers,” Barsi said.

Although there are hypotheses about why flowers originated more than 130 million years ago, the answer remains elusive.

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The UFO isn’t the only protein doing some extra work. According to Christine Foer, Professor of Plant Science at the University of Birmingham, many proteins perform important functions in addition to those for which they were first described.

said Foyer, who was not part of the research.

Nature’s Plants, 2023. DOI: 10.1038 / s41477-022-01336-2

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