apterous Aspecifies dorsal wing patterns and sexual traits in butterflies

Abstract

Butterflies have evolved different colour patterns on their dorsal and ventral wing surfaces to serve different signalling functions, yet the developmental mechanisms controlling surface-specific patterning are still unknown. Here, we mutate both copies of the transcription factor apterous in Bicyclus anynana butterflies using CRISPR/Cas9 and show that apterous A, expressed dorsally, functions both as a repressor and modifier of ventral wing colour patterns, as well as a promoter of dorsal sexual ornaments in males. We propose that the surface-specific diversification of wing patterns in butterflies proceeded via the co-option of apterous A or its downstream effectors into various gene regulatory networks involved in the differentiation of discrete wing traits. Further, interactions between apterous and sex-specific factors such as doublesex may have contributed to the origin of sexually dimorphic surface-specific patterns. Finally, we discuss the evolution of eyespot number diversity in the family Nymphalidae within the context of developmental constraints due to apterous regulation.

Sub‐micrometer insights into the cytoskeletal dynamics and ultrastructural diversity of butterfly wing scales

“…Thus, it can be expected that the scale cell precursors from different eyespot rings maintain differential expression in the following stages, and the combination of single‐cell transcriptomics with single‐scale phenomics could yield interesting insights on the gene regulatory networks that lead scale cells toward distinct morphologies. The workflow can also be used in combination with reverse genetics approach; indeed, CRISPR knock‐outs of candidate wing patterning genes generate mosaic mutant clones with sharp boundaries, at least when the targeted genes have a cell autonomous function. For instance, knock‐outs of the optix transcription factor affects both pigment composition and structural coloration, suggesting a master role for scale identity .…”

Butterfly eyespot color pattern formation requires physical contact of the pupal wing epithelium with extracellular materials for morphogenic signal propagation

“…Real-time bioimaging techniques for monitoring developing wing epithelial cells have helped to understand their dynamic nature; for example, peripheral adjustment, contraction movements, coloration order, overpainting of colors, elongation of cellular structures, cytoneme-like horizontal processes, and calcium waves have been discovered [43][44][45][46][47][48]. The CRISPR/Cas9 genome-editing system has led to the functional identification of molecules involved in eyespot development [49][50][51][52][53][54][55][56], which has complemented and fortified previous molecular approaches with analyses of gene expression patterns [57][58][59][60][61][62][63][64], transgenics [64], RNAi [65], and baculovirus-mediated gene transfer [66]. Some of the functionally tested molecules may be considered "molecular morphogens".…”

How to study enhancers in non-traditional insect models

“…Since the first breakthrough application of the CRISPR/Cas9 system in genome editing in 2012 and 2013 (Cong et al, 2013;Jinek et al, 2012), CRISPR/Cas9-based knockout techniques have already been applied to various orders of non-traditional model insects and other arthropod species [e.g. Coleoptera (Gilles et al, 2015), Lepidoptera (Connahs et al, 2019;Mazo-Vargas et al, 2017;Prakash and Monteiro, 2018;Wei et al, 2014;Zhang and Reed, 2016), Hymenoptera (Trible et al, 2017;Yan et al, 2017), Orthoptera (Watanabe et al, 2017), Zygentoma (Ohde et al, 2018) and crustacean species (Martin et al, 2016;Nakanishi et al, 2014), reviewed in Gantz and Akbari, 2018;Gilles and Averof, 2014], showing the relative ease of adopting this technique in insects.…”

“…This approach has been very successful in butterflies (e.g. Connahs et al, 2019;Mazo-Vargas et al, 2017;Prakash and Monteiro, 2018;Zhang and Reed, 2016;Zhang et al, 2017a,b) as well as in other species such as in the crustacean Parhyale (Bruce and Patel, 2018 preprint;Clark-Hachtel and Tomoyasu, 2017 preprint;Martin et al, 2016). However, to be able to detect mutant phenotypes in G0, (1) genome editing events need to happen in a large enough number of somatic cells and (2) mutant phenotypes need to be clearly visible (e.g.…”