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Butterfly color patterns provide visible and biodiverse phenotypic readouts of the patterning processes. While the secreted ligand WntA was shown to instruct the color pattern formation in butterflies, its mode of reception remains elusive. Butterfly genomes encode four homologues of the Frizzled-family of Wnt receptors. Here we show that CRISPR mosaic knock-outs of frizzled2 (fz2) phenocopy the color pattern effects of WntA loss-of-function in multiple nymphalids. While WntA mosaic clones result in intermediate patterns of reduced size, fz2 clones are cell-autonomous, consistent with a morphogen function. Shifts in expression of WntA and fz2 in WntA crispant pupae show that they are under positive and negative feedback, respectively. Fz1 is required for Wnt-independent planar cell polarity (PCP) in the wing epithelium. Fz3 and Fz4 show phenotypes consistent with Wnt competitive-antagonist functions in vein formation (Fz3 and Fz4), wing margin specification (Fz3), and color patterning in the Discalis and Marginal Band Systems (Fz4). Overall, these data show that the WntA/Frizzled2 morphogen-receptor pair forms a signaling axis that instructs butterfly color patterning, and shed light on the functional diversity of insect Frizzled receptors.
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Porcupine/Wntless‐dependent trafficking of the conserved WntA ligand in butterflies
Abstract Wnt ligands are key signaling molecules in animals, but little is known about the evolutionary dynamics and mode of action of the WntA orthologs, which are not present in the vertebrates or inDrosophila. Here we show that the WntA subfamily evolved at the base of the Bilateria + Cnidaria clade, and conserved the thumb region and Ser209 acylation site present in most other Wnts, suggesting WntA requires the core Wnt secretory pathway. WntA proteins are distinguishable from other Wnts by a synapomorphic Iso/Val/Ala216 amino‐acid residue that replaces the otherwise ubiquitous Thr216 position.WntAembryonic expression is conserved between beetles and butterflies, suggesting functionality, but theWntAgene was lost three times within arthropods, in podoplean copepods, in the cyclorrhaphan fly radiation, and in ensiferan crickets and katydids. Finally, CRISPR mosaic knockouts (KOs) ofporcupineandwntlessphenocopied the pattern‐specific effects ofWntAKOs in the wings ofVanessa carduibutterflies. These results highlight the molecular conservation of the WntA protein across invertebrates, and imply it functions as a typical Wnt ligand that is acylated and secreted through the Porcupine/Wntless secretory pathway.
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- PAR ID:
- 10229705
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
- Volume:
- 336
- Issue:
- 6
- ISSN:
- 1552-5007
- Page Range / eLocation ID:
- p. 470-481
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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