title: Neofunctionalization of a Duplicate dachshund Gene Underlies the Evolution of a Novel Leg Segment in Arachnids.
abstract: The acquisition of a novel function, or neofunctionalization, protects duplicated genes from redundancy and subsequent loss, and is a major force that drives adaptive evolution. Neofunctionalization has been inferred for many duplicated genes based on differences in regulation between the parental gene and its duplicate. However, only few studies actually link the new function of a duplicated gene to a novel morphological or physiological character of the organism. Here we show that the duplication of dachshund (dac) in arachnids (spiders and allies) is linked with the evolution of a novel leg segment, the patella. We have studied dac genes in two distantly related spider species, the entelegyne spider Parasteatoda tepidariorum and the haplogyne spider Pholcus phalangioides. Both species possess two paralogous dac genes that duplicated before the split between entelegyne and haplogyne spiders. In contrast to the evolutionarily highly conserved dac1, its duplicate dac2 is strongly expressed in the patella leg segment during embryogenesis in both species. Using parental RNA interference in P. tepidariorum we show that dac2 is required for the development of the patella segment. If dac2 function is impaired, then the patella is fused with the tibia into a single leg segment. Thus, removing the function of dac2 experimentally reverts P. tepidariorum leg morphology into a stage before the duplication of dac and the evolution of the patella segment. Our results indicate that the origin of the patella is the result of the duplication and subsequent neofunctionalization of dac in the arachnid lineage.
authors.affiliation: Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universität, Göttingen, Germany.
authors.forename: Natascha
authors.initials: N
authors.lastname: Turetzek
authors.affiliation: Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universität, Göttingen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Pechmann
authors.affiliation: Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universität, Göttingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schomburg
authors.affiliation: Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universität, Göttingen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Schneider
authors.affiliation: Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Georg-August-Universität, Göttingen, Germany nprpic@uni-goettingen.de.
authors.forename: Nikola-Michael
authors.initials: NM
authors.lastname: Prpic
mesh_terms: D000595:Amino Acid Sequence; D000825:Animal Structures / Q000254:growth & development; D000818:Animals; D001097:Arachnida / Q000235:genetics* / Q000254:growth & development*; D060829:Arthropod Proteins / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian; D005260:Female; D020440:Gene Duplication / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D016415:Sequence Alignment
chemical_list: D060829:Arthropod Proteins; D009687:Nuclear Proteins
keywords: arachnids; dachshund; gene duplication; leg segmentation; morphological novelty; neofunctionalization