Whitehead Institute scientists have determined that a plant protein involved in the timing of flowering could in fact be a prion. This is the first time that a possible prion has been identified in plants.
Infamous for causing fatal degenerative brain diseases, such as bovine spongiform encephalopathy, known more commonly as "mad cow disease," Creutzfeldt-Jakob disease, and scrapie, prions are proteins that have the ability to self-perpetuate when they assume a particular conformation. They can be inherited separately from DNA.
Although prions are typically associated with negative effects, recent research from Whitehead Member Susan Lindquist's lab has shown that prions can introduce evolutionarily beneficial traits that help an organism survive environmental stresses. Lindquist's lab has identified such prions in yeast, including several that are able to regulate transcription, translation, and RNA processing.
In the current work, which is reported online this week in the journal PNAS, researchers in the Lindquist lab screened protein fragments from Arabidopsis thaliana, a relative of the mustard plant, and identified 474 that contain prion-like domains. Of those, the team, led by postdoctoral researcher Sohini Chakrabortee, focused on four prion candidates in the autonomous flowering pathway, which controls the timing of flowering in response to yet-unknown internal cues.
To see if the candidates have the properties of prions, the scientists inserted the proteins into yeast, a model that the Lindquist lab has studied extensively. After testing the candidates with several tools used to identify prions, the scientists determined that one of the proteins, called Luminidependens (LD), has several traits associated with prions and could maintain a heritable, self-perpetuating state.
"We weren't surprised that a plant could have a prion. It would be more surprising if only yeast and mammals have prions and nothing else does," says Can Kayatekin, a postdoctoral researcher who is an author of the PNAS paper. "While more work needs to be done to show these proteins do indeed function as prions in plants, clearly it is a very real possibility. We hope this work can motivate scientists to be the lookout for prions in plants."
Greg Newby, a Lindquist graduate student and another author of the paper agrees.
"This fundamental research expands our view of where functional prions may act," adds Newby. "I wonder how many organisms and cellular pathways may utilize prion propagation."
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