Extreme Evolutionary Conservation of Functionally Important Regions in H1N1 Influenza Proteome
Figure 1
Phylogenetic relationships, species derivation and relative evolutionary rates for 75 accessions of H1N1 influenza.
Shown is the topology inferred for the HA protein (see subsection Inference of patterns of molecular evolution for surface and interior residues in Methods); other proteins show somewhat differing relationships (Supporting Information). We also show the ratio of surface-to-interior amino acid substitutions (re/ri), calculated as the difference between the branch lengths estimated from the exterior and interior residues. Variation in re/ri is illustrated from low to high with colors from blue to pink. Each colored box represents the organism of origin: Avian (yellow), Human (beige), and Swine (green). We note that the lower clade (separated by a dashed line) is composed almost entirely of human-derived strains, with the exception of one swine accession (Tianjin/01/2004). This clade also shows a fairly clear timeline (cyan). The upper clade, however, does not give such clear indications of timing.