Wickett, Norman J. , Fan, Yu , Lewis, Paul O. , Goffinet, Bernard .
Plastid genome decay in parasitic plants: insight from the non-photosynthetic liverwort Aneura mirabilis.
The recently annotated, complete plastid genome sequence of the parasitic liverwort Aneura mirabilis revealed the complete functional loss of the chlororespiration (ndh) genes, pseudogenes for major subunits of photosystem I, photosystem II, and the cytochrome b6f complex, and an inversion of psbE and petL. The designation of pseudogenes was made using genomic comparisons with the phylogenetically distant liverwort Marchantia polymorpha. In order to correlate functional gene losses with the evolution of a heterotrophic life history, we sampled several populations of A. mirabilis and its photosynthetic sister groups and sequenced plastid regions homologous with the losses detected in the plastid genome sequence. A functional gene loss or the psbE-petL inversion was never detected in a photosynthetic liverwort. All the gene losses and the psbE-petL inversion were detected in every population of the non-photosynthetic liverwort sampled. The rates of synonymous and non-synonymous substitutions were estimated for eight pseudogenes and six genes to detect whether they are evolving under relaxed purifying selection. Here we present evidence that A. mirabilis has recently acquired an obligately heterotrophic life history, and that large deletions and structural rearrangements may play an important role in the functional reduction of the plastid genome, rather than a relaxation of a synonymous substitution bias, early in the shift to parasitism.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - University of Connecitcut, Ecology and Evolutionary Biology, 75 N. Eagleville Rd., Storrs, CT, 06268, United States
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Huron/Hilton
Date: Monday, July 9th, 2007
Time: 5:00 PM