The Plastid Genome of Polytoma uvella Is the Largest Known among Colorless Algae and Plants and Reflects Contrasting Evolutionary Paths to Nonphotosynthetic Lifestyles

The loss of photosynthesis is frequently associated with parasitic or pathogenic lifestyles, but it also can occur in free-living, plastid-bearing lineages. A common consequence of becoming nonphotosynthetic is the reduction in size and gene content of the plastid genome. In exceptional circumstances, it can even result in the complete loss of the plastid DNA (ptDNA) and its associated gene expression system, as reported recently in several...