Modular organization of Peptaibol synthetases and proposed evolution by tandem duplication. A domains from peptaibol synthetases form three distinct, well-supported clades in the EAS subfamily (Fig. 7). A. Modular structure of the H. virens TEX 1 peptaibol synthetase and two peptaibol synthetases in the related species, T. reesii (T.reesii 2_23171 and T.reesii 2_123786. Color coding corresponds to clades identified in phylogenetic analyses (B and C, and Fig. 7). Arrows indicate bootstrap support for module relationships (B, C. and Fig. 7). While T. reesii 2_23171 is clearly a homolog of TEX1, domain duplication of modules 18 to 19 or vice versa and addition of module 2 have occurred since the common ancestor of these species. B. Two of the peptaibol synthetases clades (light green and dark blue, Fig. 7), group together as a monophyletic group but without bootstrap support. A domains shown in stippled boxes indicate modules from T.reesii 2_123786 which do not have a clear counterpart in the other peptaibol synthetases and may represent ancestral domains. C. The third clade (purple, Fig. 7) groups in a distinct position within the EAS subtree.