Insight into nuclear body formation of phytochromes through stochastic modelling and experiment

Ramon Grima, Sebastian Sonntag, Filippo Venezia, Stefan Kircher, Robert W. Smith, Christian Fleck

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)

Abstract

Spatial relocalization of proteins is crucial for the correct functioning of living cells. An interesting example of spatial ordering is the light-induced clustering of plant photoreceptor proteins. Upon irradiation by white or red light, the red light-active phytochrome, phytochrome B, enters the nucleus and accumulates in large nuclear bodies (NBs). The underlying physical process of nuclear body formation remains unclear, but phytochrome B is thought to coagulate via a simple protein-protein binding process. We measure, for the first time, the distribution of the number of phytochrome B-containing NBs as well as their volume distribution. We show that the experimental data cannot be explained by a stochastic model of nuclear body formation via simple protein-protein binding processes using physically meaningful parameter values. Rather modelling suggests that the data is consistent with a two step process: a fast nucleation step leading to macroparticles followed by a subsequent slow step in which the macroparticles bind to form the nuclear body. An alternative explanation for the observed nuclear body distribution is that the phytochromes bind to a so far unknown molecular structure. We believe it is likely this result holds more generally for other nuclear body-forming plant photoreceptors and proteins.

Original languageEnglish
Article number056003
JournalPhysical Biology
Volume15
Issue number5
DOIs
Publication statusPublished - 18 May 2018

Keywords

  • biological physics
  • nuclear bodies
  • phytochrome signaling
  • plant biology
  • stochastic modelling

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