Macroevolutionary shifts of WntA function potentiate butterfly wing-pattern diversity

Area of Science:

• Developmental Biology
• Evolutionary Genetics
• Insect Morphology

Background:

• Butterfly wing patterns offer insights into the evolution of morphological complexity.
• The gene WntA is a known hotspot for shape-tuning alleles related to wing mimicry.

Purpose of the Study:

• To investigate the role of the signaling ligand gene WntA in butterfly wing pattern formation using CRISPR/Cas9 somatic mutagenesis.
• To understand how WntA contributes to the diversity of wing patterns across different nymphalid species.

Main Methods:

• CRISPR/Cas9 somatic mutagenesis was employed to induce loss-of-function mutations in WntA.
• The effects of WntA loss-of-function on wing pattern elements were analyzed in seven nymphalid butterfly species.

Main Results:

• WntA loss-of-function resulted in significant modifications to wing pattern elements across multiple species.
• WntA was essential for inducing symmetry systems (stripe-like patterns) in some species and acted as an eyespot activator in others.
• The gene specified boundaries between color fields in Heliconius and showed dual roles in Agraulis, with divergent functions in monarch butterflies.

Conclusions:

• WntA acts as an instructive signal for prepatterning diverse butterfly wing patterns.
• Changes in WntA's deployment and function illustrate how a single developmental gene can drive significant morphological evolution.