title: Toll Genes Have an Ancestral Role in Axis Elongation.
abstract: One of the key morphogenetic processes used during development is the controlled intercalation of cells between their neighbors. This process has been co-opted into a range of developmental events, and it also underlies an event that occurs in each major group of bilaterians: elongation of the embryo along the anterior-posterior axis [1]. In Drosophila, a novel component of this process was recently discovered by Paré et al., who showed that three Toll genes function together to drive cell intercalation during germband extension [2]. This finding raises the question of whether this role of Toll genes is an evolutionary novelty of flies or a general mechanism of embryonic morphogenesis. Here we show that the Toll gene function in axis elongation is, in fact, widely conserved among arthropods. First, we functionally demonstrate that two Toll genes are required for cell intercalation in the beetle Tribolium castaneum. We then show that these genes belong to a previously undescribed Toll subfamily and that members of this subfamily exhibit striped expression (as seen in Tribolium and previously reported in Drosophila [3-5]) in embryos of six other arthropod species spanning the entire phylum. Last, we show that two of these Toll genes are required for normal morphogenesis during anterior-posterior embryo elongation in the spider Parasteatoda tepidariorum, a member of the most basally branching arthropod lineage. From our findings, we hypothesize that Toll genes had a morphogenetic function in embryo elongation in the last common ancestor of all arthropods, which existed over 550 million years ago.
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany. Electronic address: matthewabenton@gmail.com.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Benton
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Pechmann
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Frey
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Stappert
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany.
authors.forename: Kai H
authors.initials: KH
authors.lastname: Conrads
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany.
authors.forename: Yen-Ta
authors.initials: YT
authors.lastname: Chen
authors.affiliation: Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Stamataki
authors.affiliation: Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Pavlopoulos
authors.affiliation: Institute for Developmental Biology, University of Cologne, 50674 Cologne, North-Rhine Westphalia, Germany. Electronic address: siegfried.roth@uni-koeln.de.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Roth
mesh_terms: D033304:Amphipoda / Q000196:embryology / Q000235:genetics; D000818:Animals; D004330:Drosophila; D019476:Insect Proteins / Q000235:genetics*; D009024:Morphogenesis; D013112:Spiders / Q000196:embryology / Q000235:genetics*; D051193:Toll-Like Receptors / Q000235:genetics*; D014231:Tribolium / Q000196:embryology / Q000235:genetics*
chemical_list: D019476:Insect Proteins; D051193:Toll-Like Receptors