Stationary Patterns in a Two-Protein Reaction-Diffusion System

Abstract

Patterns formed by reaction-diffusion mechanisms are crucial for the development or sustenance of most organisms in nature. Patterns include dynamic waves, but are more often found as static distributions, such as animal skin patterns. Yet, a simplistic biological model system to reproduce and quantitatively investigate static reactiondiffusion patterns has been missing so far. Here, we demonstrate that the Escherichia coli Min system, known for its oscillatory behavior between the cell poles, is under certain conditions capable of transitioning to quasi-stationary protein distributions on membranes closely resembling Turing patterns. We systematically titrated both proteins, MinD and MinE, and found that removing all purification tags and linkers from the N-terminus of MinE was critical for static patterns to occur. At small bulk heights, dynamic patterns dominate, such as in rod-shaped microcompartments. We see implications of this work for studying pattern formation in general, but also for creating artificial gradients as downstream cues in synthetic biology applications.

Bulk-surface coupling reconciles Min-protein pattern formationin vitroandin vivo

“…Our in vitro experiments in laterally wide, flat microchambers with a well-controlled finite height showed that the Min-protein interactions can yield dramatically different patterns by changing only the height of the confining chamber and the E:D ratio. While the important role of total densities as control parameters was shown before (both in theoretical (37,39,52) and experimental (23,27) studies) our findings show that the bulk height, or more generally the bulk-surface ratio, is an equally important control parameter. This parameter determines how far concentration gradients can penetrate into the cytosol in the direction normal to the membrane.…”

“…The Min system was discovered in E. coli (14,15), and subsequently purified and reconstituted in vitro on supported lipid bilayers that mimic the cell membrane (16). This reconstitution provides a minimal system that enables precise control of reaction parameters and geometrical constraints (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). This enabled the study of the patternformation process and its molecular mechanism in a well-controlled manner, and showed the ability of the Min system to form a rich plethora of dynamic patterns, predominantly travelling waves and spirals, but also "mushrooms", "snakes", "amoebas", "bursts" (16,17,28) as well as quasi-static labyrinths, spots, and mesh-like patterns (26,27).…”

Adaptability and evolution of the cell polarization machinery in budding yeast

“…The repeated switching of MinD polarity due to redistribution of MinE is what gives rise to the Min oscillations in E. coli. Recently also stationary Min patterns have been observed in vitro (Glock et al, 2019). Conversely, oscillatory Cdc42 dynamics are found in the fission yeast S. Pombe , and have also been indirectly observed in budding yeast mutants Ozbudak et al, 2005).…”

Flow Induced Symmetry Breaking in a Conceptual Polarity Model

“…We expect that the insights obtained from the minimal two-component model studied here generalize to systems with more components and multiple protein species. For example, in vitro studies of the reconstituted MinDE system of E. coli show that MinD and MinE spontaneously form dynamic membrane-bound patterns, including spiral waves [48] and quasi-stationary patterns [49]. These patterns emerge from the competition of MinD self-recruitment and MinE-mediated detachment of MinD [50,51].…”