Fig. 1. Phylogenetic analysis of T-box genes. (A) Phylogenetic tree. T-box domain amino acid sequences of all C. elegans T-box genes and representative members of the defined T-box subfamilies found in other organisms (Papaioannou, 2001) were aligned using ClustalW accessed via the European Bioinformatics Institute (EBI, http://www.ebi.ac.uk/). The alignment was subjected to Phylip analysis using the same EBI interface and Phylip outputs were interpreted using the tree drawing programme TreeView. Non-C. elegans genes are in red. Species abbreviations are as follows: As, ascidian; Dm, Drosophila melanogaster; Hs, Homo sapiens; Mm, Mus musculus. New C. elegans gene names (tbx-30-41) have been approved by the Caenorhabditis Genetics Centre (CGC). (B) Genomic organisation of tbx-8 and tbx-9 (and neighbouring genes) in C. elegans and C. briggsae. Ce-tbx-8 and Ce-tbx-9 are transcribed in opposing directions (arrows), whereas Cb-tbx-8 and Cb-tbx-9 are transcribed in the same direction (arrows). The thick dotted line represents the intergenic region. Ce-tbx-8 and Cb-tbx-8 are 73% identical throughout their T-box domains. Ce-tbx-9 and Cb-tbx-9 are 56% identical. There is evidence of a local chromosome inversion in C. briggsae compared with C. elegans, which extends for several genes to the right of Cb-tbx-9 (neighbouring region not drawn to scale). Red bar denotes the T-box domain of Ce-tbx-8 and Ce-tbx-9 (59% identical).