Molecular Ecology and Evolution
Braukmann, Thomas , Kuzmina, Maria , Stefanovic, Sasa .
Fine-scale evolution of plastid genomes across Cuscuta (Convolvulaceae): Extensive loss of plastid genes within two clades of subgenus Grammica.
The genus Cuscuta, found within Convolvulaceae (the morning glory family), is one of the most investigated lineages of parasitic plants. Whole plastome sequencing of exemplar species within this genus has demonstrated changes to both plastid gene content and structure, but maintenance of photosynthetic and photorespiratory genes is observed. The presence of these genes under purifying selection indicates that Cuscuta is cryptically photosynthetic. However, plastid genome content across the diversity of this genus (~180 species) remains largely unknown. A fine-scale comparative investigation of plastid genome content, grounded within a phylogenetic framework, was conducted using a slot-blot Southern hybridization approach. We extensively sampled across Cuscuta, including within two clades (Kand O) previously reported to possess much more altered plastomes compared to other members of this genus. Fifty-six probes derived from all categories of protein coding genes typically found within the plastomes of flowering plants were used. Our results indicate that clades 'O' and 'K' exhibit far more plastid gene loss relative to other members of Cuscuta. All surveyed members of the 'O' clade show extensive loss of plastid genes from every category of genes typically found in the plastome, including otherwise highly conserved ribosomal subunits. The extent of plastid gene losses within this clade is similar to that observed in Rafflesiaceae in which the very presence of a plastome has previously been questioned. The 'K' clade also exhibits considerable loss of plastid genes. Unlike in the 'O' clade in which all species seem to be affected, the losses in this clade are progressive, culminating in C. erosa and C. strobilaceae. This presents an ideal opportunity to study the reduction of the plastome in holoparasites 'in action'. The widespread plastid gene loss in these two clades is hypothesized to be a consequence of the complete loss of photosynthesis. Additionally, we identify taxa that would be ideal for entire plastome sequencing to further investigate the loss of photosynthesis and reduction of the plastome within Cuscuta.
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1 - University of Toronto Mississauga, Department of Biology, 3359 Mississauga Rd N, Mississauga, ON, L5L 1C6, Canada
2 - Canadian Center for DNA Barcoding, Guelph, ON
Presentation Type: Oral Paper:Papers for Topics
Location: Union B/Hyatt
Date: Monday, July 9th, 2012
Time: 1:45 PM