RT Journal Article SR Electronic T1 Repeated co-option of a conserved gene regulatory module underpins the evolution of the crustacean carapace, insect wings and other flat outgrowths JF bioRxiv FD Cold Spring Harbor Laboratory SP 160010 DO 10.1101/160010 A1 Yasuhiro Shiga A1 Yasuhiko Kato A1 Yuko Aragane-Nomura A1 Takayuki Haraguchi A1 Theodora Saridaki A1 Hajime Watanabe A1 Taisen Iguchi A1 Hideo Yamagata A1 Michalis Averof YR 2017 UL http://biorxiv.org/content/early/2017/07/06/160010.abstract AB Summary statement The genes vestigial, scalloped and wingless comprise a conserved regulatory module that was co-opted repeatedly for the evolution of flat structures, such as insect wings, and crustacean carapace, tergites and coxal plates.Summary How novelties arise is a key question in evolutionary developmental biology. The crustacean carapace is a novelty that evolved in the early Cambrian. In an extant crustacean, Daphnia magna, the carapace grows from the body wall as a double-layered sheet with a specialized margin. We show that the growing margin of this carapace expresses vestigial, scalloped and wingless, genes that are known to play key roles in regulating growth at the insect wing margin. RNAi-mediated knockdown of scalloped and wingless impair carapace development, indicating that carapace and wing might share a common mechanism for margin outgrowth. However, carapace and wings arise in different parts of the body and their margins have different orientations, arguing that these structures have independent evolutionary origins. We show that scalloped is also expressed at the margin of unrelated flat outgrowths (tergites and coxal plates) in the distantly related crustacean Parhyale hawaiensis. Based on these observations, we propose that the vestigial-scalloped-wingless gene module has a common role in the margin of diverse flat structures, originating before the divergence of major crustacean lineages and the emergence of insects. Repeated co-option of this module occurred independently in the carapace, wing and other flat outgrowths, underpinning the evolution of distinct novelties in different arthropod lineages.