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Down the slippery slope: plastid genome evolution in Convolvulaceae
Sasa Stefanović1, Richard G Olmstead
1Department of Biology, University of Washington, Box 355325, Seattle, WA, 98195-5325, USA. sstefano@utm.utoronto.ca
Journal of Molecular Evolution
|July 7, 2005
Summary
The plastid genome of parasitic Cuscuta (dodder) reveals structural rearrangements. Many changes are ancestral or unique to specific taxa, with few linked to its parasitic lifestyle.
Area of Science:
- Plant Biology
- Genomics
- Evolutionary Biology
Background:
- Cuscuta (dodder) is the sole parasitic genus within the Convolvulaceae (morning-glory) family.
- The holoparasitic subgenus Grammica within Cuscuta remains poorly investigated regarding its plastid genome.
- Understanding plastid genome evolution in parasitic plants offers insights into plant adaptation and diversification.
Purpose of the Study:
- To determine the size, structure, gene content, and synteny of the plastid genome in Cuscuta sandwichiana.
- To compare the Cuscuta plastid genome with that of tobacco and other Cuscuta subgenera.
- To investigate the role of plastid genome rearrangements in the evolution of parasitic plants.
Main Methods:
- Long PCR was employed to obtain large portions of the plastid genome sequence from Cuscuta sandwichiana.
- Comparative genomics was used, contrasting the Cuscuta genome with the tobacco chloroplast genome and other Cuscuta taxa.
- Molecular phylogenetic frameworks were utilized to analyze structural rearrangements within the Convolvulaceae family.
Main Results:
- Three categories of plastid genome rearrangements were identified in Cuscuta: plesiomorphic, autapomorphic, and synapomorphic.
- Many observed changes in Cuscuta are ancestral (plesiomorphic) or unique to specific Cuscuta taxa (autapomorphic), not solely adaptations to parasitism.
- Synapomorphic rearrangements, exclusive to Cuscuta, are most likely linked to its parasitic lifestyle, though many affected regions have unknown or no apparent function.
Conclusions:
- Plastid genome evolution in Cuscuta is shaped by a combination of ancestral traits, lineage-specific changes, and adaptations related to parasitism.
- The parasitic lifestyle of Cuscuta is associated with specific synapomorphic rearrangements in its plastid genome.
- Further research is needed to elucidate the function of numerous open reading frames and non-coding regions within the Cuscuta plastid genome.