Periodic temperature changes drive the proliferation of self-replicating RNAs in vesicle populations

Abstract

Growth and division of biological cells are based on the complex orchestration of spatiotemporally controlled reactions driven by highly evolved proteins. In contrast, it remains unknown how their primordial predecessors could achieve a stable inheritance of cytosolic components before the advent of translation. An attractive scenario assumes that periodic changes of environmental conditions acted as pacemakers for the proliferation of early protocells. Using catalytic RNA (ribozymes) as models for primitive biocatalytic molecules, we demonstrate that the repeated freezing and thawing of aqueous solutions enables the assembly of active ribozymes from inactive precursors encapsulated in separate lipid vesicle populations. Furthermore, we show that encapsulated ribozyme replicators can overcome freezing-induced content loss and successive dilution by freeze-thaw driven propagation in feedstock vesicles. Thus, cyclic freezing and melting of aqueous solvents – a plausible physicochemical driver likely present on early Earth – provides a simple scenario that uncouples compartment growth and division from RNA self-replication, while maintaining the propagation of these replicators inside new vesicle populations.

Spatiotemporal Propagation of a Minimal Catalytic RNA Network in GUV Protocells by Temperature Cycling and Phase Separation

“…Concentrations were 0.5 μM (A, B*, F, poly U) and 3 mM (spermine). Red fluorescence intensity before FT is due to a quenching efficiency of less than 100 % ( � 92 % [28] ). C) Schematic of control experiment implemented at the same concentrations as in (B) but in the absence of spermine and poly U.…”

Raumzeitliche Propagation eines minimalen katalytischen RNA‐Netzwerkes in GUV‐Protozellen durch Temperaturzyklen und Phasenseparation

“…Die Konzentrationen betrugen 0.5 μM (A, B*, F, Poly‐U) and 3 mM (Spermin). Das schwache rote Fluoreszenzsignal vor dem FT‐Zyklus ist auf eine nicht 100 %‐ige Quenchingeffizienz (≈92 % [28] ) zurückzuführen. C) Schematische Darstellung eines Kontrollexperiments, welches ohne Spermin und Poly‐U unter ansonsten gleichen Bedingungen durchgeführt wurde.…”

“…Innerhalb der Lebensspanne von Bakterien werden deren Membranen im Zuge der Zellteilung transformiert, [29] während das Genom durch die Replisom-Maschinerie reversibel kondensiert und dekondensiert wird. [30] Es Das schwache rote Fluoreszenzsignal vor dem FT-Zyklus ist auf eine nicht 100 %-ige Quenchingeffizienz ( � 92 % [28] ) zurückzuführen.…”

Elucidating the Mechanism of Freeze‐Thaw Driven Content Mixing between Protocells

“…The confocal images in Figure 1 suggest that freezing and thawing also leads to a reduction in vesicle size, which has previously been analyzed by our group in greater detail. [27]…”

“…[26] Moreover, we have shown in other studies that such cyclic temperature changes can be exploited to propagate catalytically active RNAs within a population of GUVs and that the presence of temperature-sensitive RNA organelles can even improve the propagation of such minimal catalytic RNA networks by implementing spatiotemporal control in GUVs. [27,28] Relating to the phase transition of membrane lipids, we hypothesized that transient periods of membrane destabilization result in an increased permeability allowing for a diffusion-based mixing of contents across vesicle membranes. It has long been established that membranes reach a maximum in permeability in the regime of lipid phase transition between the fluid and the gel phase.…”