News Release

Genome editing and butterfly wing patterns

Peer-Reviewed Publication

Proceedings of the National Academy of Sciences

<i>Junonia coenia</i> Wing Scales (1 of 3)

image: Mosaic deletion of optix replaces pigmentation with blue structural iridescence in Junonia coenia wing scales. view more 

Credit: Image courtesy of Roxanne Conowitch.

Researchers use genome editing to explore how certain genes influence butterfly wing colors and patterns. Gene association, mapping, and expression studies have helped link the optix gene to pattern variation in butterfly wings. However, the gene's function remains unclear. Robert Reed and colleagues used CRISPR-Cas9 genome editing to inactivate the optix gene in nymphalid butterflies from four species: the red postman (Heliconius erato), the Gulf fritillary (Agraulis vanillae), the painted lady (Vanessa cardui), and the common buckeye (Junonia coenia). In all four species, black pigment replaced red and orange pigment when optix was deleted, with corresponding changes in expression of genes involved in pigment production. In the common buckeye, deleting optix also induced structural changes in wing scales that resulted in blue iridescence. The resulting wing patterns resembled the archetypal "black-and-blue" wing patterns found in multiple butterfly species and that appear to have evolved independently of each other. According to the authors, optix might function as a switch that toggles wing scales between different color states through coordinated changes in pigmentation and structure, and whose function is conserved across diverse butterfly genera. In a related study, Arnaud Martin and colleagues used a similar method to inactivate the WntA signaling ligand gene in seven nymphalid butterfly species. Butterfly WntA mutants from three species with a conserved pattern configuration had missing or distorted stripe-like patterns known as symmetry systems. The authors further showed that this gene has evolved additional functions in species that deviate from the conserved configuration. In V. cardui, WntA inactivation inhibited formation of forewing eyespots. In Heliconius species, WntA inactivation led to loss of the boundaries of bright color patches involved in toxic mimicry. In monarchs, which lack symmetry systems, WntA deactivation led to the expansion of white interveinous patterns. The results illustrate how evolutionary modifications to the expression and effects of a developmental gene can give rise to morphological diversity, according to the authors.

###

Article #17-08149: "Macroevolutionary shifts of WntA function potentiate butterfly wing-pattern diversity," by Anyi Mazo-Vargas et al.

MEDIA CONTACT: Arnaud Martin, George Washington University, Washington, DC; tel: 949-302-3296; e-mail: <arnaud@gwu.edu>

Article #17-09058: "Single master regulatory gene coordinates the evolution and development of butterfly color and iridescence," by Linlin Zhang, Anyi Mazo-Vargas, and Robert D. Reed.

MEDIA CONTACT: Robert D. Reed, Cornell University, Ithaca, NY; tel: 607-254-1315, 919-451-5420; e-mail: <robertreed@cornell.edu>


Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.