Arnaud Martin

Cortex cis-regulatory switches establish scale colour identity and pattern diversity in Heliconius

Publisher: eLife Sciences Publications, Ltd

Date: 19-07-2021

DOI: 10.7554/ELIFE.68549

Abstract: In Heliconius butterflies, wing colour pattern ersity and scale types are controlled by a few genes of large effect that regulate colour pattern switches between morphs and species across a large mimetic radiation. One of these genes, cortex , has been repeatedly associated with colour pattern evolution in butterflies. Here we carried out CRISPR knockouts in multiple Heliconius species and show that cortex is a major determinant of scale cell identity. Chromatin accessibility profiling and introgression scans identified cis -regulatory regions associated with discrete phenotypic switches. CRISPR perturbation of these regions in black hindwing genotypes recreated a yellow bar, revealing their spatially limited activity. In the H. melpomene/timareta lineage, the candidate CRE from yellow-barred phenotype morphs is interrupted by a transposable element, suggesting that cis -regulatory structural variation underlies these mimetic adaptations. Our work shows that cortex functionally controls scale colour fate and that its cis -regulatory regions control a phenotypic switch in a modular and pattern-specific fashion.

Interplay between Developmental Flexibility and Determinism in the Evolution of Mimetic Heliconius Wing Patterns

Publisher: Elsevier BV

Date: 12-2019

DOI: 10.1016/J.CUB.2019.10.010

Abstract: To what extent can we predict how evolution occurs? Do genetic architectures and developmental processes canalize the evolution of similar outcomes in a predictable manner? Or do historical contingencies impose alternative pathways to answer the same challenge? Ex les of Müllerian mimicry between distantly related butterfly species provide natural replicates of evolution, allowing us to test whether identical wing patterns followed parallel or novel trajectories. Here, we explore the role that the signaling ligand WntA plays in generating mimetic wing patterns in Heliconius butterflies, a group with extraordinary mimicry-related wing pattern ersity. The radiation is relatively young, and numerous cases of wing pattern mimicry have evolved within the last 2.5-4.5 Ma. WntA is an important target of natural selection and is one of four major effect loci that underlie much of the pattern variation in the group. We used CRISPR/Cas9 targeted mutagenesis to generate WntA-deficient wings in 12 species and a further 10 intraspecific variants, including three co-mimetic pairs. In all tested butterflies, WntA knockouts affect pattern broadly and cause a shift among every possible scale cell type. Interestingly, the co-mimics lacking WntA were very different, suggesting that the gene networks that pattern a wing have erged considerably among different lineages. Thus, although natural selection channeled phenotypic convergence, ergent developmental contexts between the two major Heliconius lineages opened different developmental routes to evolve resemblance. Consequently, even under very deterministic evolutionary scenarios, our results underscore a surprising unpredictability in the developmental paths underlying convergence in a recent radiation.

University Of California, Irvine

Location: United States of America

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University Of California, Berkeley

Location: United States of America

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George Washington University

Location: United States of America

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École Normale Supérieure De Lyon

Location: France

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Cornell University

Location: United States of America

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