Plant protein acts like a prion

Prion proteins have a notorious reputation. These types of proteins can fold into conformations that coax other prions to join them, leading to the formation of insoluble protein aggregates. This is the mechanism behind some neurodegenerative diseases such as Creutzfeldt-Jakob, mad cow, and maybe Alzheimer’s disease.

But not all prions are bad. In the past decade, researchers have found that some organisms, such as yeast, flies, and even mammals, use prions’ self-propagating clumping as part of normal cellular functions.

Now, a team of scientists reports the first protein in plants that exhibits prion behavior (Proc. Natl. Acad. Sci.USA 2016, DOI: 10.1073/pnas.1604478113). The findings provide further evidence that prions are more than just disease-causing abnormalities of the protein world.

Susan Lindquist of the Whitehead Institute for Biomedical Research and colleagues looked at suspected prion domains in three proteins from the flowering plant Arabidopsis thaliana.

To test for prion behavior, the team replaced the prion domain of a well-studied yeast protein, Sup35, with the suspected prion domains of each of the candidates. Once inserted into yeast, the candidate domain from the flowering protein luminidependens acted like Sup35, showing that the plant protein could behave like a prion in yeast.

Lindquist says researchers still need to show that the protein acts like a prion in the plant itself. The team hypothesizes the prion might play a role in helping the plant determine when to flower by storing information about the length of winters, a process called vernalization.

But plant molecular biologist Scott Michaels of Indiana University, Bloomington, points out that although luminidependens helps regulate flowering, it is not involved in vernalization pathways.

Still, he thinks the work raises an interesting question of how the plants might rely on the prion mechanism.

According to Lindquist, the findings demonstrate how prion behavior can be found in many organisms. “Prions are famous for how bad they can be,” she says. “We really need to open our eyes and see that they’re not just bad things and look for them in other places.”