Fig. 1. Genomic clustering, gene structure and phylogenetic analysis of the T-box genes Doc1, Doc2 and Doc3. (A) Arrangement of the three Dorsocross genes within a genomic region of about 40 kb. CG5194 is a predicted gene with no similarity to any known gene. The exon structures of Doc cDNAs are depicted below with the coding sequences hatched and the T-box domains in black. The exon-intron structure with the T-box spanning exons 2 to exons 5 is conserved among Doc1, Doc2 variant A and Doc3. (B) ClustalX-generated alignment of T-box domains from T-box genes of Drosophila melanogaster (Doc1, Doc2, Doc3, omb/optomotor-blind, H15, H15r/H15-related/CG6634, org-1/omb-related gene 1, byn/brachyenteron/trg) and human (marked Hs). Additional Tbx6/16-related members of the T-box family, which appear to form a separate subgroup, are included from zebrafish (Dr) and Xenopus laevis (Xl). The T-box core sequence was N- and C-terminally extended in order to include amino acids partially conserved between subfamily members. (C) Phylogenetic N-J tree derived from ClustalX analysis, based on the alignment shown in B and using 1000 bootstrap trials (bootstrap values at tree node represent confidence values; branches with values below 700 are generally considered as less reliable and below 500 as unreliable. Bar represents amino acid exchanges as a fraction of 1). Caenorhabditis elegans (Ce) Tbx9 was included as an outgroup member. GenBank Accession Numbers are, for Doc2A, AAM11544; for Doc2B, AAM11545; and for Doc3, AAM11543. A Doc1 protein sequence identical to ours has previously been submitted by R. Murakami and T. Hamaguchi (AB035412).