Xenogenous DNA in Chloroplast Genomes?
Kowallik, K.V., Laatsch, T., Nitsch, T., Stöbe, B., Behn, W.
Botany Department, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1,
D-40225 Düsseldorf, Germany
Genomes of extant chloroplast lineages reflect streamlined cyanobacterial genomes. They evolved mainly by gene loss and gene translocation to the host’s nucleus in primary and secondary endosymbioses. Gene uptake from sources outside the chloroplast is less well documented and is believed to have occurred only rarely, if at all. We present data from chloroplast genomes of siphonaceous marine green algae that contain genes which have not been found in cyanobacteria or chloroplasts to date. In Bryopsis plumosa a 25 kbp insertion within the chloroplast genome contains presumably untranscribed reading frames of unusual sizes, together with short direct repeats known from viruses and eukaryotic chromosomes. One of the large, and partially duplicated, reading frames is homologous to eubacterial DNA polymerases. Sequences of putatively xenogenous origin are also found in the closely related Derbesia marina chloroplast genome. In addition, numerous group I and group II introns in Bryopsis chloroplast genes containing reading frames for endonucleases and reverse transcriptases/maturases reflect secondary introns unknown from cyanobacteria and most other chloroplast lineages. A scenario will be discussed which suggests that chloroplast genomes may acquire and stably integrate xenogenous DNA during evolution.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Thursday, April 9 |
03:35 pm |