PT  - JOURNAL ARTICLE
AU  - Andrea Del Cortona
AU  - Frederik Leliaert
AU  - Kenny A. Bogaert
AU  - Monique Turmel
AU  - Christian Boedeker
AU  - Jan Janouškovec
AU  - Juan M. Lopez-Bautista
AU  - Heroen Verbruggen
AU  - Klaas Vandepoele
AU  - Olivier De Clerck
TI  - The plastid genome in Cladophorales green algae is encoded by hairpin plasmids
AID  - 10.1101/145037
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 145037
4099  - http://biorxiv.org/content/early/2017/06/08/145037.short
4100  - http://biorxiv.org/content/early/2017/06/08/145037.full
AB  - Chloroplast genomes, relics of an endosymbiotic cyanobacterial genome, are circular double-stranded DNA molecules. While fragmented mitochondrial genomes evolved several times during the evolution of eukaryotes, fragmented plastid genomes are only known in dinoflagellates. Here we show that the chloroplast genome of the green alga Boodlea composita (Cladophorales) is reduced and fragmented into hairpin plasmids. Extensive sequencing of DNA and RNA demonstrated that the chloroplast genome is fragmented into 1-7 kb, GC-rich DNA contigs, each containing a long inverted repeat with protein-coding genes and conserved non-coding region. These contigs correspond to linear single-stranded DNA molecules that fold onto themselves to form hairpin plasmids. An elevated transfer of chloroplast genes to the nucleus coincided to Boodlea chloroplast genome reduction. The genes retained in the chloroplast are highly divergent from their corresponding orthologs. A chloroplast genome that is composed only of linear DNA molecules is unprecedented among eukaryotes.One Sentence Summary Chloroplast genome in Cladophorales green algae is reduced and fragmented into multiple linear single-stranded DNA molecules.