Extended Data Fig. 2. Evolution of the extant lineages of marine planktonic cyanobacteria and its relationship to HpnP gene loss.

HpnP was likely lost long before the emergence of extant planktonic marine species. The dated species tree is adapted from a recent molecular clock study (see Supplementary Fig. 6 for the original figure with the species annotation)⁵⁴. Presence/absence of HpnP in individual sub-clades was inferred from Supplementary Table 5 and recently-published phylogenomic studies of Cyanobacteria^55,56. Inference for the vertical inheritance of the HpnP gene (solid line) is based on Fig. 3. Several representative HpnP-containing species are shown next to the corresponding clades. Asterisks indicate that the species is closely related to the corresponding clade, but is not included in the dataset in the cited study. Light blue circles indicate the possible timing of HpnP gene loss in the lineages that include modern marine planktonic species. It is noted that the timing of HpnP gene loss is possibly even earlier, depending on the actual HpnP evolutionary history in Cyanobacteria (dashed lines; vertical inheritance vs. horizontal transfer). Figure adapted from ref. ⁵⁴ under a Creative Commons license CC BY 4.0.