Authors
Susann Wicke, Kai F Müller, Claude W DePamphilis, Dietmar Quandt, Sidonie Bellot, Gerald M Schneeweiss
Publication date
2016/8/9
Journal
Proceedings of the National Academy of Sciences
Volume
113
Issue
32
Pages
9045-9050
Publisher
National Academy of Sciences
Description
Because novel environmental conditions alter the selection pressure on genes or entire subgenomes, adaptive and nonadaptive changes will leave a measurable signature in the genomes, shaping their molecular evolution. We present herein a model of the trajectory of plastid genome evolution under progressively relaxed functional constraints during the transition from autotrophy to a nonphotosynthetic parasitic lifestyle. We show that relaxed purifying selection in all plastid genes is linked to obligate parasitism, characterized by the parasite’s dependence on a host to fulfill its life cycle, rather than the loss of photosynthesis. Evolutionary rates and selection pressure coevolve with macrostructural and microstructural changes, the extent of functional reduction, and the establishment of the obligate parasitic lifestyle. Inferred bursts of gene losses coincide with periods of relaxed selection, which are followed by …
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