No phylogenetic evidence for ménage à trois at origin of plants

Primary plastids descend from the cyanobacterial endosymbiont of an ancient eukaryotic host, but the initial selective drivers that stabilized the association between these two cells are still unclear. According to the ménage à trois hypothesis, chlamydiae have facilitated the establishment of the primary plastid by mediating metabolic interactions between cyanobacteria and the eukaryotic host.  In a joint Nature Communications paper Daryl Domman and Matthias Horn with Tom Williams and Martin Embley (University of Newcastle) now show that that there is no compelling evidence from gene trees for a contribution of chlamydiae to the establishment of the primary plastid.