Plastid Origins
نویسنده
چکیده
The evolution of oxygenic photosynthesis in the ancestors of present-day cyanobacteria transformed the biosphere of our planet (Blankenship 1994; ReyesPrieto et al. 2007). This landmark event was also an essential prerequisite for the evolution of photosynthetic eukaryotes. Plastids, or chloroplasts, are the lightgathering organelles of algae and plants whose origin can be traced back to cyanobacteria. Mereschkowsky (1905) is usually credited as being the first biologist to speculate on the possible evolutionary significance of similarities between cyanobacteria and plastids, and in the era of molecular biology and genomics, the evidence that plastids are derived from once free-living prokaryotes is now beyond refute. Modern-day plastids and the eukaryotes that harbor them are remarkably diverse in their morphology and biochemistry, but are nevertheless sufficiently similar to one another in their core features to be able to infer common ancestry. These include similarities in their plastid light-harvesting apparatus, the existence of protein import machinery with many cyanobacterial features, and an organellar genome of demonstrable cyanobacterial ancestry (Kim and Archibald 2009). This chapter provides an overview of the origin and diversification of plastids across the eukaryotic tree of life, an area of basic research that has benefited tremendously from advances in genomics and molecular biology. Genome sequences from an evolutionarily diverse array of eukaryotic phototrophs are now available and have made it possible to sketch a general picture of how plastids evolved. Yet, while the evidence in support of a cyanobacterial origin for plastids is stronger than ever, other questions pertaining to the biology and evolution of
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تاریخ انتشار 2017