A phylogenetic tree of the Wnt genes based on all available full-length sequences, including five from the cephalochordate amphioxus

The Wnt gene family is large, and new members are still being discovered. W e constructed a parsimony tree for the Wnt family based on all 82 of the fu ll-length sequences currently available. The inclusion of sequences from th e cephalochordate amphioxus is especially useful in comprehensive gene tree s, because the amphioxus genes in each subfamily often mark the base of the vertebrate diversification. We thus isolated full-length cDNAs of five amp hioxus War genes (AmphiWnt1, AmphiWnt4, AmphiWnt7, AmphiWnt8, and AmphiWnt1 1) for addition to the overall War family tree. The analysis combined amino acid and nucleotide sequences (excluding third codon positions), taking in to account 97% of the available data for each sequence. This combinatorial method had the advantage of generating a single most-parsimonious tree that was trichotomy-free. The reliability of the nodes was assessed by both jac kknifing and Bremer support (decay index). A regression analysis revealed t hat branch length was strongly correlated with branch support, and possible reasons for this pattern are discussed. The tree topology suggested that i n amphioxus, at least an AmphiWnt5 and an AmphiWnt10 have yet to be discove red.