Phylogenetic tree obtained by amino acid sequence comparison of different TGF-βs. The phylogenetic tree was constructed from a single multiple alignment, using neighbor-joining method with Clustal X 2.0.8 and MEGA 4.0 tools. Numbers at the tree nodes represent percentage bootstrap values after 1000 replicates. *denotes the cloned TGF-β from S. aurata in the current study. For each sequence, NCBI or Ensembl accession number and species abbreviation are shown. Few fish species with only partial sequences available were included as well and are denoted by #. Full scientific names of species abbreviations, common names and their respective accession numbers are detailed in Additional file 2.