University of British Columbia, Department of Botany, 3529-6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
Curr Opin Genet Dev. 2019 Oct;58-59:1-8. doi: 10.1016/j.gde.2019.07.014. Epub 2019 Aug 27.
Whether mitochondria and plastids originated by endosymbiosis is no longer questioned, but we still do not understand the actual process of integration. Other, younger endosymbiotic systems are, however, relatively common. Traditionally, it was not clear whether these systems could be directly and informatively compared to organelles because they appear sufficiently different. Surprisingly, new data from both organelles and endosymbiotic bacteria are changing this view. As more commonalities are described, the processes underlaying these associations appear to be not so different after all. New models for endosymbiotic associations emphasize the importance of transient stages, conflict more than cooperation, and population genetics forces that lead to genome reduction, which in turn restricts most endosymbionts to one of a few possible evolutionary pathways, commonly ending with extinction.
线粒体和质体是否通过内共生起源已不再受到质疑，但我们仍不了解其实际的融合过程。然而，其他相对年轻的内共生系统则较为常见。传统上，由于这些系统看起来差异足够大，因此不清楚它们是否可以直接且有意义地与细胞器进行比较。令人惊讶的是，来自细胞器和内共生细菌的新数据正在改变这一观点。随着更多共性被描述出来，这些关联背后的过程似乎并没有那么不同。内共生关联的新模型强调了短暂阶段的重要性、冲突多于合作以及种群遗传学力量，这些力量导致基因组减少，从而限制了大多数内共生体只能沿着少数几种可能的进化途径之一发展，最终通常以灭绝而告终。
