Barbrook Adrian C, Howe Christopher J, Purton Saul
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, UK.
Trends Plant Sci. 2006 Feb;11(2):101-8. doi: 10.1016/j.tplants.2005.12.004. Epub 2006 Jan 9.
The evolution of the plastid from a photosynthetic bacterial endosymbiont involved a dramatic reduction in the complexity of the plastid genome, with many genes either discarded or transferred to the nucleus of the eukaryotic host. However, this evolutionary process has not gone to completion and a subset of genes remains in all plastids examined to date. The various hypotheses put forward to explain the retention of the plastid genome have tended to focus on the need for photosynthetic organisms to retain a genetic system in the chloroplast, and they fail to explain why heterotrophic plants and algae, and the apicomplexan parasites all retain a genome in their non-photosynthetic plastids. Here we consider two additional explanations: the 'essential tRNAs' hypothesis and the 'transfer-window' hypothesis.
质体从光合细菌内共生体的进化过程涉及质体基因组复杂性的显著降低，许多基因要么被丢弃，要么转移到真核宿主的细胞核中。然而，这一进化过程尚未完成，至今在所有被检测的质体中仍保留着一部分基因。为解释质体基因组保留现象而提出的各种假说往往侧重于光合生物在叶绿体中保留遗传系统的必要性，但它们无法解释为什么异养植物和藻类以及顶复门寄生虫在其非光合质体中都保留了一个基因组。在这里，我们考虑另外两种解释：“必需tRNA”假说和“转移窗口”假说。
