title: FGF signaling repertoire of the indirect developing hemichordate Ptychodera flava.
abstract: Fibroblast growth factors (FGFs) are a group of ligands that play multiple roles during development by transducing signals through FGF receptors (FGFRs) to downstream factors. At least 22 FGF ligands and 4 receptors have been identified in vertebrates, while six to eight FGF ligands and a single FGFR are present in invertebrate chordates, such as tunicates and amphioxus. The chordate FGFs can be categorized into at least seven subfamilies, and the members of which expanded during the evolution of early vertebrates. In contrast, only one FGF and two FGFRs have been found in sea urchins. Thus, it is unclear whether the FGF subfamilies duplicated in the lineage leading to the chordates, or sea urchins lost several fgf genes. Analyses of the FGF signaling repertoire in hemichordates, which together with echinoderms form the closest group to the chordates, may provide insights into the evolution of FGF signaling in deuterostomes. In this study, we identified five FGFs and three FGFRs from Ptychodera flava, an indirect-developing hemichordate acorn worm. Phylogenetic analyses revealed that hemichordates possess a conserved FGF8/17/18 in addition to several putative hemichordate-specific FGFs. Analyses of sequence similarity and protein domain organizations suggested that the sea urchin and hemichordate FGFRs arose from independent lineage-specific duplications. Furthermore, the acorn worm fgf and fgfr genes were demonstrated to be expressed during P. flava embryogenesis. These results set the foundations for further functional studies of FGF signaling in hemichordates and provided insights into the evolutionary history of the FGF repertoire.
authors.affiliation: Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan; Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 40227, Taiwan.
authors.forename: Tzu-Pei
authors.initials: TP
authors.lastname: Fan
authors.affiliation: Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan; Biotechnology Center, National Chung-Hsing University, Taichung 40227, Taiwan. Electronic address: yhsu@gate.sinica.edu.tw.
authors.forename: Yi-Hsien
authors.initials: YH
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002816:Chordata, Nonvertebrate / Q000235:genetics / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D017468:Receptors, Fibroblast Growth Factor; D005346:Fibroblast Growth Factors
keywords: Ambulacraria; FGF; Hemichordate; Ptychodera flava