Mizuuchi Ryo, Lehman Niles
Department of Chemistry, Portland State University, Portland, OR 97207, USA.
Life (Basel). 2019 Feb 21;9(1):20. doi: 10.3390/life9010020.
The origins of life require the emergence of informational polymers capable of reproduction. In the RNA world on the primordial Earth, reproducible RNA molecules would have arisen from a mixture of compositionally biased, poorly available, short RNA sequences in prebiotic environments. However, it remains unclear what level of sequence diversity within a small subset of population is required to initiate RNA reproduction by prebiotic mechanisms. Here, using a simulation for template-directed recombination and ligation, we explore the effect of sequence diversity in a given population for the onset of RNA reproduction. We show that RNA reproduction is improbable in low and high diversity of finite populations; however, it could robustly occur in an intermediate sequence diversity. The intermediate range broadens toward higher diversity as population size increases. We also found that emergent reproducible RNAs likely form autocatalytic networks and collectively reproduce by catalyzing the formation of each other, allowing the expansion of information capacity. These results highlight the potential of abiotic RNAs, neither abundant nor diverse, to kick-start autocatalytic reproduction through spontaneous network formation.
生命的起源需要能够进行复制的信息聚合物的出现。在原始地球上的RNA世界中，可复制的RNA分子可能起源于益生元环境中成分有偏差、可用性差的短RNA序列的混合物。然而，目前尚不清楚在一小部分群体中需要何种程度的序列多样性才能通过益生元机制启动RNA复制。在这里，我们使用模板导向的重组和连接模拟，探讨给定群体中的序列多样性对RNA复制起始的影响。我们表明，在有限群体的低多样性和高多样性情况下，RNA复制不太可能发生；然而，它可能在中等序列多样性中稳健地发生。随着群体规模的增加，中间范围向更高的多样性扩展。我们还发现，出现的可复制RNA可能形成自催化网络，并通过催化彼此的形成来集体复制，从而实现信息容量的扩展。这些结果突出了既不丰富也不多样的非生物RNA通过自发形成网络启动自催化复制的潜力。
