Spontaneous network formation among cooperative RNA replicators

摘要

在有关以仅有RNA为特征的早期生命的模型rn中，人们曾提出，如果RNA分子能够相互作rn用、而不是独立发挥功能的话，生命和演化rn将会更容易实现。它们的确能够相互作用。rnNiles Lehman及其同事利用包含能够组装成rn核酶的RNA片段的一个模型系统在试管中确rn认了这个概念。他们发现，由这些片段形成rn的合作性网络能够竞争过自催化的RNA片段。rn这项工作表明，RNA分子具有通过合成形成更rn大复杂性的内在能力，也说明这种行为所具rn有的好处在地球上的生命形成过程的早期已rn经确立。%The origins of life on Earth required the establishment of self-replicating chemical systems capable of maintaining and evolving biological information. In an RNA world, single self-replicating RNAs would have faced the extreme challenge of possessing a mutation rate low enough both to sustain their own information and to compete successfully against molecular parasites with limited evolvability. Thus theoretical analyses suggest that networks of interacting molecules were more likely to develop and sustain life-like behaviour. Here we show that mixtures of RNA fragments that self-assemble into self-replicating ribozymes spontaneously form cooperative catalytic cycles and networks. We find that a specific three-membered network has highly cooperative growth dynamics. When such cooperative networks are competed directly against selfish autocatalytic cycles, the former grow faster, indicating an intrinsic ability of RNA populations to evolve greater complexity through cooperation. We can observe the evolvability of networks through in vitro selection. Our experiments highlight the advantages of cooperative behaviour even at the molecular stages of nascent life.