Evolution in red algal plastid genomes caused by horizontal gene transfer events

Abstract

Red algae have played an important role as primary producers in marine coastal ecosystems. Red algae also played a critical role in the evolutionary history of algae because they were the plastid donor in a secondary endosymbiotic event that gave rise to the chlorophyll c containing algae (heterokonts, cryptophytes, haptophytes and alveolates). Despite the significance of this plastid donor role, only ten plastid genomes have been reported from the more than 6000 red algal species. To fill the gap of our understanding of plastid evolution, we determined and haracterized complete plastid genomes from three red algal species - Sporolithon durum, Gelidium elegans and G. vagum.The plastid genome sizes are 191, 174, and 179 kb, respectively. Sporolithon durum contained 205 genes while G. elegans and G. vagum included 200 genes, and all three contain three rRNAs and 30 tRNAs. We discovered several specific horizontal gene transfers. We will discuss evolutionary scenarios for these horizontal gene transfer events.t gave rise to the chlorophyll c containing algae (heterokonts, cryptophytes, haptophytes and alveolates). Despite the significance of this plastid donor role, only ten plastid genomes have been reported from the more than 6000 red algal species. To fill the gap of our understanding of plastid evolution, we determined and haracterized complete plastid genomes from three red algal species - Sporolithon durum, Gelidium elegans and G. vagum.The plastid genome sizes are 191, 174, and 179 kb, respectively. Sporolithon durum contained 205 genes while G. elegans and G. vagum included 200 genes, and all three contain three rRNAs and 30 tRNAs. We discovered several specific horizontal gene transfers. We will discuss evolutionary scenarios for these horizontal gene transfer events.