The emergence of ribozymes synthesizing membrane components in RNA-based protocells.

A significant problem of the origin of life is the emergence of cellular self-replication. In the context of the "RNA world", a crucial concern is how the RNA-based protocells could achieve the ability to produce their own membrane. Here we show, with the aid of a computer simulation, that for these protocells, there would be "immediately" a selection pressure for the emergence of a ribozyme synthesizing membrane components. The ribozyme would promote the enlargement of cellular space and favor the incoming (by permeation) of RNA's precursors, thus benefit the replication of inner RNA, including itself. Via growth and division, protocells containing the ribozyme would achieve superiority and spread in the system, and meanwhile the ribozyme would spread in the system. The present work is inspiring because it suggests that the transition from molecular self-replication to cellular self-replication might have occurred naturally (and necessarily) in the origin of life, leading to the emergence of Darwinian evolution at the cellular level. 2009 Elsevier Ireland Ltd. All rights reserved.