生物多样性 ›› 2016, Vol. 24 ›› Issue (8): 966-976.DOI: 10.17520/biods.2016057

• • 上一篇    

细胞核和有性生殖是如何起源的?

谢平*()   

  1. 中国科学院水生生物研究所, 武汉 430072
  • 收稿日期:2016-02-28 接受日期:2016-07-12 出版日期:2016-08-20 发布日期:2016-09-02
  • 通讯作者: 谢平

How did nucleus and sexual reproduction come into being?

Ping Xie*()   

  1. Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072
  • Received:2016-02-28 Accepted:2016-07-12 Online:2016-08-20 Published:2016-09-02
  • Contact: Xie Ping

摘要:

真核生物的起源是一个根本性的、令人生畏的进化谜题, 目前设想的关于“核”起源的流行情景还远谈不上清晰。关于真核生物的起源可谓众说纷纭, 有共营模型、自演化模型、病毒性真核生物起源模型和外膜假说, 等等。迄今为止, 真核演化的动因则鲜有涉及。笔者发现, 从原核生物到真核生物, 基因组的DNA总量大约增加了3.5个数量级, 而这与现代真核生物的DNA压缩比(packing ratio)惊人地一致! 这样, 仅仅用偶然的吞噬、共生或寄生来解释真核生物的起源, 无论如何是难以让人信服的(其实, 正是内共生理论将人们引入了歧途), 而关键是需要解释基因组为何急剧增大。这可能与DNA的复制错误或多倍化现象不无关系, 当然并非完全排除不同种类个体之间的侧向的基因流动或整合的可能贡献。不难理解, DNA压缩机制的成型应该就是迈向真核生物的关键一步, 自然还伴随了细胞内部的结构分化、更为精巧而复杂的细胞分裂机制的发展, 等等。因此, 本文提出细胞核起源的新学说——压缩与结构化假说。此外, 从分子遗传学的角度来说, “性”一点都不神秘, 就是将两个个体的基因组拼在一起而已, 藉此种族多样的遗传信息分散到了个体之中; 而从生态的角度来看, “性”的原始动机就是与休眠事件的偶联。

关键词: 真核的起源, DNA, 染色体, 压缩比, 压缩与结构化假说, 有性生殖, 休眠事件假说

Abstract:

The origin of eukaryote is a fundamental, forbidding evolutionary puzzle, and the popular scenarios of eukaryogenesis are far from being clear. So far, there have been various theories (e.g., syntrophic model, autogenous model, viral eukaryogenesis model, exomembrane hypothesis), but few explain why. I observed that C-value (the amount of DNA contained within a haploid nucleus) increased by 3.5 orders of magnitude from prokaryote to eukaryotes, which is inconceivably close to the packing ratio of DNA in extant eukaryotes. Thus, it is never convincing to explain eukaryogenesis solely by using accident phagocytosis, symbiosis or parasitism (the influential endosymbiont theory unfortunately took the wrong turning!), but what is important is to explain why genome increased so sharply. This may be mainly related to DNA replication errors or polyploidization, of course not completely ruling out the possible contribution from lateral gene flow or genetic integration between individuals of different species. It is above suspicion that successful packing of DNA (finally into chromosome) was a key step towards eukaryogenesis, of course also accompanied with structural differentiation in cell and development of more subtle and complex cell division, and so on. This paper presents “packing and structurization hypothesis” to explain eukaryogenesis. In addition, from a molecular genetic point of view, sexual reproduction is never a mystery as it is just a process to merge two individual genomes, by which diverse genetic information of the species are dispersed into its individuals. On the other hand, from an ecological point of view, the original motivation of “sex” was accidently coupled with dormancy.

Key words: eukaryogenesis, DNA, chromosome, packing ratio, “packing and structurization hypothesis”, sexual reproduction, accident dormancy hypothesis