Mazo-Vargas, Anyi, Concha, Carolina, Livraghi, Luca, Massardo, Darli, Wallbank, Richard W. R., Zhang, Linlin, Papador, Joseph D., Martinez-Najera, Daniel, Jiggins, Chris D., Kronforst, Marcus R., Breuker, Casper J., Reed, Robert D., Patel, Nipam H., McMillan, W. O., and Martin, Arnaud. 2017. "Macroevolutionary shifts of WntA function potentiate butterfly wing-pattern diversity." Proceedings of the National Academy of Sciences of the United States of America, 114, (40) 10701–10706. https://doi.org/10.1073/pnas.1708149114.
Butterfly wing patterns provide a rich comparative framework to study how morphological complexity develops and evolves. Here we used CRISPR/Cas9 somatic mutagenesis to test a patterning role for WntA, a signaling ligand gene previously identified as a hotspot of shape-tuning alleles involved in wing mimicry. We show that WntA loss-of-function causes multiple modifications of pattern elements in seven nymphalid butterfly species. In three butterflies with a conserved wing-pattern arrangement, WntA is necessary for the induction of stripe-like patterns known as symmetry systems and acquired a novel eyespot activator role specific to Vanessa forewings. In two Heliconius species, WntA specifies the boundaries between melanic fields and the light-color patterns that they contour. In the passionvine butterfly Agraulis, WntA removal shows opposite effects on adjacent pattern elements, revealing a dual role across the wing field. Finally, WntA acquired a divergent role in the patterning of interveinous patterns in the monarch, a basal nymphalid butterfly that lacks stripe-like symmetry systems. These results identify WntA as an instructive signal for the prepatterning of a biological system of exuberant diversity and illustrate how shifts in the deployment and effects of a single developmental gene underlie morphological change.
