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Evolutionary variation in the wing pigmentation of butterflies and moths offers striking examples of adaptation by crypsis and mimicry. Thecortexlocus has been independently mapped as the locus controlling color polymorphisms in 15 lepidopteran species, suggesting that it acts as a genomic hotspot for the diversification of wing patterns, but functional validation through protein-coding knockouts has proven difficult to obtain. Our study unveils the role of a long noncoding RNA (lncRNA) which we nameivory, transcribed from thecortexlocus, in modulating color patterning in butterflies. Strikingly,ivoryexpression prefigures most melanic patterns during pupal development, suggesting an early developmental role in specifying scale identity. To test this, we generated CRISPR mosaic knock-outs in five nymphalid butterfly species and show thativorymutagenesis yields transformations of dark pigmented scales into white or light-colored scales. Genotyping ofVanessa carduigermline mutants associates these phenotypes to small on-target deletions at the conserved first exon ofivory. In contrast,cortexgermline mutant butterflies with confirmed null alleles lack any wing phenotype and exclude a color patterning role for this adjacent gene. Overall, these results show that a lncRNA gene acts as a master switch of color pattern specification and played key roles in the adaptive diversification of wing patterns in butterflies.
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Multiple roles for laccase2 in butterfly wing pigmentation, scale development, and cuticle tanning
Abstract Lepidopteran wing scales play important roles in a number of functions including color patterning and thermoregulation. Despite the importance of wing scales, however, we still have a limited understanding of the genetic mechanisms that underlie scale patterning, development, and coloration. Here, we explore the function of the phenoloxidase‐encoding genelaccase2in wing and scale development in the nymphalid butterflyVanessa cardui. Somatic deletion mosaics oflaccase2generated by CRISPR/Cas9 genome editing presented several distinct mutant phenotypes. Consistent with the work in other nonlepidopteran insect groups, we observed reductions in melanin pigmentation and defects in cuticle formation. We were also surprised, however, to see distinct effects on scale development including complete loss of wing scales. This study highlightslaccase2as a gene that plays multiple roles in wing and scale development and provides new insight into the evolution of lepidopteran wing coloration.
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- Award ID(s):
- 1656514
- PAR ID:
- 10176206
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Evolution & Development
- Volume:
- 22
- Issue:
- 4
- ISSN:
- 1520-541X
- Page Range / eLocation ID:
- p. 336-341
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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