Evolutionary scenarios on the cyanobacterial and eukaryotic ancestral gnd gene distribution in bikonts. A, Traditional view of host cell phylogeny of bikonts [e.g. 45], assuming the multiple loss events of eukaryotic ancestral genes and at least two lateral gene transfer events (LGT) of cyanobacterial genes (broken lines plus white arrows). B, Alternative phylogeny [e.g. 19], assuming a single loss and a single lateral gene transfer event. Although only either the cyanobacterial or eukaryotic ancestral gene was found in Excavata in this study, only one is illustrated for clarity. Rhizaria is not shown since no gnd genes have been found in this lineage. 2nd EGT, secondary endosymbiotic gene transfer.