Patterns in evolutionary origins of heme, chlorophyll <i>a</i> and isopentenyl diphosphate biosynthetic pathways suggest non-photosynthetic periods prior to plastid replacements in dinoflagellates

Abstract

Pioneering works hypothesized that the ancestral kareniacean species had lost the photosynthetic activity prior to haptophyte endosymbiosis. The absence of VI-type proteins in the Chl <i>a</i> biosynthetic pathway in <i>Karenia</i> or <i>Karlodinium</i> is in good agreement with the putative non-photosynthetic nature proposed for their ancestor. The dominance of proteins with haptophyte origin in the <i>Karenia</i>/<i>Karlodinium</i> pathway suggests that their ancestor rebuilt the particular pathway by genes acquired from the endosymbiont. Likewise, we here propose that the ancestral <i>Lepidodinium</i> likely experienced a non-photosynthetic period and discarded the entire Chl <i>a</i> biosynthetic pathway prior to the green algal endosymbiosis. Nevertheless, <i>Lepidodinium</i> rebuilt the pathway by genes transferred from phylogenetically diverse organisms, rather than the green algal endosymbiont. We explore the reasons why green algal genes were barely utilized to reconstruct the <i>Lepidodinium</i> pathway.