Figure 1.

Evolution of the Nos gene family. (a) Phylogenetic analysis of Nos proteins in chordates. The tree topology was inferred by Bayesian inference and maximum-likelihood methods, with the exact topology obtained from the former shown here (see the electronic supplementary material, figure S7 for the maximum-likelihood tree). Numbers at nodes represent posterior probability values (left) and maximum-likelihood bootstrap support for 1000 replicates (right). (b,c), Evolutionary scenarios indicating the loss of Nos2 event in Neoteleostei (b) and Nos3 in Clupeocephala (c) as grey lines. Nos3 in Elopomorpha is absent, although parsimony suggests it was present in stem elopomorphs, and it is indicated with a dashed line. TGD stands for teleost-specific genome duplication. (Online version in colour.)