title: Knockdown of Parhyale Ultrabithorax recapitulates evolutionary changes in crustacean appendage morphology.
abstract: Crustaceans possess remarkably diverse appendages, both between segments of a single individual as well as between species. Previous studies in a wide range of crustaceans have demonstrated a correlation between the anterior expression boundary of the homeotic (Hox) gene Ultrabithorax (Ubx) and the location and number of specialized thoracic feeding appendages, called maxillipeds. Given that Hox genes regulate regional identity in organisms as diverse as mice and flies, these observations in crustaceans led to the hypothesis that Ubx expression regulates the number of maxillipeds and that evolutionary changes in Ubx expression have generated various aspects of crustacean appendage diversity. Specifically, evolutionary changes in the expression boundary of Ubx have resulted in crustacean species with either 0, 1, 2, or 3 pairs of thoracic maxillipeds. Here we test this hypothesis by altering the expression of Ubx in Parhyale hawaiensis, a crustacean that normally possesses a single pair of maxillipeds. By reducing Ubx expression, we can generate Parhyale with additional maxillipeds in a pattern reminiscent of that seen in other crustacean species, and these morphological alterations are maintained as the animals molt and mature. These results provide critical evidence supporting the proposition that changes in Ubx expression have played a role in generating crustacean appendage diversity and lend general insights into the mechanisms of morphological evolution.
authors: Department of Integrative Biology, University of California, Berkeley, CA 94720-3140, USA.
authors: Danielle M
authors: DM
authors: Liubicich
authors: Julia M
authors: JM
authors: Serano
authors: Anastasios
authors: A
authors: Pavlopoulos
authors: Zacharias
authors: Z
authors: Kontarakis
authors: Meredith E
authors: ME
authors: Protas
authors: Elaine
authors: E
authors: Kwan
authors: Sandip
authors: S
authors: Chatterjee
authors: Khoa D
authors: KD
authors: Tran
authors: Michalis
authors: M
authors: Averof
authors: Nipam H
authors: NH
authors: Patel
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D003445:Crustacea / Q000235:genetics* / Q000378:metabolism*; D005121:Extremities; D005786:Gene Expression Regulation; D005801:Genes, Homeobox; D005821:Genetic Techniques; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D017403:In Situ Hybridization; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008954:Models, Biological; D008969:Molecular Sequence Data; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D034741:RNA, Small Interfering