Figure 1.

Distribution of phytochromes (PHY) and FDBRs (ferredoxin-dependent bilin reductases) in eukaryotes. (top) A simplified cartoon of eukaryotic evolution is shown, following the scheme of Keeling and colleagues (Burki et al. 2016). (bottom) The presence of photosynthesis, PHY and FDBRs in various taxa is indicated. Photosynthetic taxa are color-coded by plastid lineage as follows: rhodophyte, red; red-derived, dark red; glaucophyte, blue; Viridiplantae, green; green-derived, dark green. The independent primary endosymbiosis in Paulinella chromatophora and related species (Yoon et al. 2009; Kim & Park 2016) is color-coded in purple. Non-photosynthetic taxa (Amoebozoa, Fungi, Metazoa, Centrohelida) are in white and lack FDBRs. For photosynthetic taxa, the presence or absence of phytochromes and FDBRs was assessed previously (Rockwell et al. 2014b). Photosynthetic stramenopiles (Ochrophyta) have been proposed to be monophyletic (e.g., Derelle et al. 2016). The photosynthetic stramenopile Aureococcus anophagefferens lacks FDBRs. Photosynthetic alveolates (double asterisk: dinoflagellates and chromerids) contain FDBR genes, whereas nonphotosynthetic alveolates do not. Prasinophytes + streptophytes comprise the Viridiplantae. Stramenopiles, Alveolata, and Rhizaria comprise the SAR clade. +/−, variable presence within photosynthetic organisms.