Koonin Eugene V
National Center for Biotechnology Information, National Library of Medicine, National Institute of Health, Bethesda, MD, 20894, USA,
Antonie Van Leeuwenhoek. 2014 Jul;106(1):27-41. doi: 10.1007/s10482-014-0169-5. Epub 2014 Apr 23.
All life on earth can be naturally classified into cellular life forms and virus-like selfish elements, the latter being fully dependent on the former for their reproduction. Cells are reproducers that not only replicate their genome but also reproduce the cellular organization that depends on semipermeable, energy-transforming membranes and cannot be recovered from the genome alone, under the famous dictum of Rudolf Virchow, Omnis cellula e cellula. In contrast, simple selfish elements are replicators that can complete their life cycles within the host cell starting from genomic RNA or DNA alone. The origin of the cellular organization is the central and perhaps the hardest problem of evolutionary biology. I argue that the origin of cells can be understood only in conjunction with the origin and evolution of selfish genetic elements. A scenario of precellular evolution is presented that involves cohesion of the genomes of the emerging cellular life forms from primordial pools of small genetic elements that eventually segregated into hosts and parasites. I further present a model of the coevolution of primordial membranes and membrane proteins, discuss protocellular and non-cellular models of early evolution, and examine the habitats on the primordial earth that could have been conducive to precellular evolution and the origin of cells.
地球上的所有生命都可以自然地分为细胞生命形式和类病毒自私元件，后者的繁殖完全依赖于前者。细胞是繁殖者，它们不仅复制自己的基因组，还能繁殖细胞组织，这种组织依赖于半透性的、能进行能量转换的膜，仅从基因组是无法恢复的，这符合鲁道夫·魏尔肖的著名格言“细胞来自细胞”。相比之下，简单的自私元件是复制者，它们仅从基因组RNA或DNA开始，就能在宿主细胞内完成其生命周期。细胞组织的起源是进化生物学的核心问题，或许也是最棘手的问题。我认为，只有结合自私遗传元件的起源和进化，才能理解细胞的起源。本文提出了一个前细胞进化的设想，其中涉及从原始小遗传元件库中凝聚出新出现的细胞生命形式的基因组，这些元件最终分化成宿主和寄生虫。我还进一步提出了原始膜和膜蛋白共同进化的模型，讨论了早期进化的原始细胞模型和非细胞模型，并研究了原始地球上可能有利于前细胞进化和细胞起源的栖息地。
