Fig. 3

An example of homologous retrogene candidates with their parental genes retained after retroposition. Maximum likelihood tree of the homologous gene group including retrogenes encoding serine/threonine protein phosphatase PP2A, metallophosphoesterase is shown on left. Inferred evolutionary events are projected on the phylogeny. Retroposition most likely occurred before speciation of Volvox/Chlamydomonas lineage from the outgroup Chlorella lineage and was followed by retention of the parental gene in each lineage, while Chlorella lost the retrocopy. VCA – Volvox; CRE – Chlamydomonas; CSP – Chlorella. Values in each OTU indicate length of encoded protein (aa), number of exons, and number of coding exons. Bootstrap support values (≥60 %) for the calculated tree are shown on branches. Clades of distant homologs of the retro- and parental genes were collapsed and the number of collapsed sequences is shown within each clade. The tree was rooted using midpoint-rooting approach. Synteny between neighboring genes (five upstream, five downstream) is shown on the right with each color representing homologous genes. Both predicted retrogenes are syntenic to each other