Fig. 2. Identity dendrogram and phylogenetic relationships between divergent olfactory receptor sequences. (A) The complete deduced amino acid sequences of the ten XORs (see Fig.1) were aligned in Pileup, and an identity dendrogram was constructed. Two classes of receptors are clearly distinguishable: class I, comprising the receptors XB107 to XB242 and class II, including the receptors XB178 to XB154. (B) Phylogenetic tree of the amino acid sequences of ORs from different species. The open-reading frames (ORFs) of 100 known olfactory receptors were initially aligned together with the ten XOR-receptors. 14 representative receptors from chicken (GGcor7b) (S. Nef, I. Allaman, E. De Castro and P. Nef, unpublished material) (GGcor1) (Leibovici et al., 1996), rat (RNor18, RNor5) (Raming et al., 1993) (RNscrd9, RNscrg14) (Walensky et al., 1998), mouse (MMor3) (Nef et al., 1992), human (HS05691) (J. E. Lamerdin, P. M. McCready, E. Skowronski, A. W. Adamson, K. Burkhart-Schultz, L. Gordon, A. Kyle, M. Ramirez, S. Stilwagen, H. Phan et al., unpublished material) (HS1740) (Ben-Arie et al., 1994), catfish Ictalurus punctatus (ICtordb,d,e) (Ngai et al., 1993a), zebrafish Danio rerio (DRorp2-3) (Barth et al., 1997) and the ten receptors from Xenopus (XB, this study) together with the receptor LFor1 from the lamprey Lampetra fluviatilis (Freitag et al., 1999) as outgroups were then realigned and analyzed by parsimony analysis with the PHYLIP package (Joseph Felsenstein, Version 3.5c, 1995). The bootstrap-support of 100 replicates is indicated.
