In Massachussetts, Whitehead Institute scientists have determined that a plant protein involved in the timing of flowering could in fact be a prion, proteins with the ability to self-perpetuate when they assume a particular conformation. They can be inherited separately from DNA. This is the first time that a possible prion has been identified in plants.

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. The lab has identified such prions in yeast, including those able to regulate transcription, translation, and RNA processing.

Researchers in the Lindquist lab screened protein fragments from Arabidopsis thaliana and identified 474 that contain prion-like domains. Of those, the team focused on four prion candidates in the autonomous flowering pathway, which controls the timing of flowering.

To see if the candidates have the properties of prions, the scientists inserted the proteins into yeast. After testing, 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.

For more on this interesting study, read the article in the Proceedings of the National Academy of Sciences of the United States.

Fig. 2.

Phenotypic switch to [PRION+] state. (A) Sup35C assay of the different cArabPrDs. Shown is the ability of the different cArabPrD-Sup35C to grow on medium lacking adenine post (Right) or before (control; Left) transient overexpression of the corresponding cArabPrD-GFP proteins. The Sup35 PrD (NM) was used as control. (B) Strain variation [assessed in complete medium (SD-CSM)] of the [LD+]-state as indicated. (C) GFP read-through assay. [LD+] and [ld−] strains were transformed with a fusion protein containing a GFP marker preceded by a stop codon. (C, i) The two strains were analyzed with fluorescence microscopy. Read-through indicated by GFP expression was observed only in the [LD+] cells. (C, ii) Multiple replicates of the [LD+] and [ld−] strains were analyzed by flow cytometry. High (blue) and low (red) GFP gates were set such that >95% of [ld−] cells were included in the low GFP gate. Percentages of cells in these gates are shown.