Prions, the misfolded proteins that are known for causing
degenerative illnesses in animals and humans, may have been spotted for
the first time in plants.
Researchers led by Susan Lindquist,
a biologist at the Whitehead Institute for Biomedical Research in
Cambridge, Massachusetts, report that they have found a section of
protein in thale cress (Arabidopsis) that behaves like a prion when it is inserted into yeast.
In plants, the protein is called
Luminidependens (LD), and it is normally involved in responding to
daylight and controlling flowering time. When a part of the LD gene is
inserted into yeast, it produces a protein that does not fold up
normally, and which spreads this misfolded state to proteins around it
in a domino effect that causes aggregates or clumps. Later generations
of yeast cells inherit the effect: their versions of the protein also
This does not mean that plants definitely have prion-like proteins, adds Lindquist — but she thinks that it is likely.
“I’d be surprised if they weren’t there,” she says. To prove it,
researchers would need to grind up a plant and see whether they could
find a protein such as LD in several different folded states, as well as
show that any potential prion caused a misfolding cascade when added to
a test-tube of protein. Lindquist adds that because she’s not a plant
scientist — her focus is on using yeast to investigate prions — she hasn’t tried these experiments. The study is reported on 25 April in the Proceedings of the National Academy of Sciences1.
A protein in thale cress (Arabidopsis, pictured) behaves like a prion when it is expressed in yeast.
Scanning electron micrograph (SEM) of an Arabidopsis thaliana flower, also commonly known as thale cress. Some of the anthers are open, revealing pollen grains ready for dispersal. Arabidopsis was the first plant to have its entire genome sequenced and is widely used as a model organism in molecular and plant biology. Horizontal width of image is 1200 microns. Magnification 100x. (Photo by Stefan Eberhard.