Complete DNA sequences of the plastid genomes of two parasitic flowering plant species, Cuscuta reflexa and Cuscuta gronovii
Permanent link
https://hdl.handle.net/10037/1252DOI
doi:10.1186/1471-2229-7-45Date
2007-08-22Type
Journal articleTidsskriftartikkel
Peer reviewed
Abstract
Background: The holoparasitic plant genus Cuscuta comprises species with photosynthetic capacity and
functional chloroplasts as well as achlorophyllous and intermediate forms with restricted photosynthetic activity
and degenerated chloroplasts. Previous data indicated significant differences with respect to the plastid genome
coding capacity in different Cuscuta species that could correlate with their photosynthetic activity. In order to shed
light on the molecular changes accompanying the parasitic lifestyle, we sequenced the plastid chromosomes of the
two species Cuscuta reflexa and Cuscuta gronovii. Both species are capable of performing photosynthesis, albeit with
varying efficiencies. Together with the plastid genome of Epifagus virginiana, an achlorophyllous parasitic plant
whose plastid genome has been sequenced, these species represent a series of progression towards total
dependency on the host plant, ranging from reduced levels of photosynthesis in C. reflexa to a restricted
photosynthetic activity and degenerated chloroplasts in C. gronovii to an achlorophyllous state in E. virginiana.
Results: The newly sequenced plastid genomes of C. reflexa and C. gronovii reveal that the chromosome structures
are generally very similar to that of non-parasitic plants, although a number of species-specific insertions, deletions
(indels) and sequence inversions were identified. However, we observed a gradual adaptation of the plastid
genome to the different degrees of parasitism. The changes are particularly evident in C. gronovii and include (a)
the parallel losses of genes for the subunits of the plastid-encoded RNA polymerase and the corresponding
promoters from the plastid genome, (b) the first documented loss of the gene for a putative splicing factor, MatK,
from the plastid genome and (c) a significant reduction of RNA editing.
Conclusion: Overall, the comparative genomic analysis of plastid DNA from parasitic plants indicates a bias
towards a simplification of the plastid gene expression machinery as a consequence of an increasing dependency
on the host plant. A tentative assignment of the successive events in the adaptation of the plastid genomes to
parasitism can be inferred from the current data set. This includes (1) a loss of non-coding regions in
photosynthetic Cuscuta species that has resulted in a condensation of the plastid genome, (2) the simplification of
plastid gene expression in species with largely impaired photosynthetic capacity and (3) the deletion of a significant
part of the genetic information, including the information for the photosynthetic apparatus, in non-photosynthetic
parasitic plants.
Publisher
BioMed CentralCitation
BMC Plant Biology 7(2007) article no 45Metadata
Show full item recordCollections
The following license file are associated with this item: