Significance heat map of the dyads discovered at different taxonomical levels in upstream sequences of lexA orthologs. Each column represents one pattern, each row one taxon. The grey level indicates the significance score returned by dyad-analysis: black corresponds to the maximal score (sig = 41.01) obtained in the whole taxonomy, and non-significant patterns appear with a white color. Patterns are clustered by sequence similarity (Ward linkage hierarchical clustering). Taxa are ordered by depth-first-search traversal of the taxonomic tree. In order to simplify this heat map, we used a stringent threshold, by only selecting taxa having at least one predicted pattern with a significance score ≥7. We manually boxed groups of patterns corresponding to taxon-specific motifs.