| Popis: |
The evolution of mitochondria and plastids (chloroplasts) by endosymbiosis is a central tenet of modern eukaryotic cell biology. Evidence in support of a prokaryotic ancestry for these textbook organelles is now stronger than ever, but despite decades of genomics-enabled research, fundamental questions about the earliest events leading to their establishment remain unanswered. Foremost among them is the precise nature of the cells involved in these endosymbiotic mergers. Mitochondria and plastids are traditionally considered to be the products of independent, but fundamentally similar, endosymbioses involving eukaryotic hosts and bacterial endosymbionts. Such a model still holds true for plastids, but increasingly it appears that mitochondria could have evolved in a fashion quite different from this ‘classical’ scenario. In this introductory chapter we provide an overview of the primary endosymbiotic origins of mitochondria and plastids, focusing on advances coming from the latest comparative genomic and proteomic investigations. In the case of plastids, the recently evolved photosynthetic ‘organelles’ of the testate amoeba Paulinella provide a possible window on the ancient origin of canonical plastids and are thus also discussed in detail. |
