Allele‐specific knockouts reveal a role for apontic‐like in the evolutionary loss of larval melanin pigmentation in the domesticated silkworm, Bombyx mori. Issue 6 (12th July 2022)

• Record Type: Journal Article
• Authors: Tomihara, Kenta; Andolfatto, Peter; Kiuchi, Takashi
• Is Part Of: Insect molecular biology. Volume 31:Issue 6(2022)
• Page Start: 701
• Page End: 710
• Publication Date: 2022-07-12
• Subjects: Bombyx mandarina -- CRISPR/Cas9 -- domestication -- pigmentation -- reciprocal hemizygosity test; Insects -- Molecular aspects -- Periodicals; 595.7
• DOI: 10.1111/imb.12797
• Languages: English
• ISSNs: 0962-1075

Abstract

Abstract: The domesticated silkworm, Bombyx mori, and its wild progenitor, B. mandarina, are extensively studied as a model case of the evolutionary process of domestication. A conspicuous difference between these species is the dramatic reduction in melanin pigmentation in both larval and adult B. mori . Here we evaluate the efficiency of CRISPR/Cas9‐targeted knockouts of pigment‐related genes as a tool to understand their potential contributions to domestication‐associated melanin pigmentation loss in B. mori . To demonstrate the efficacy of targeted knockouts in B. mandarina, we generated a homozygous CRISPR/Cas9‐targeted knockout of yellow‐y. In yellow‐y knockout mutants, black body colour became lighter throughout the larval, pupal and adult stages, confirming a role for this gene in melanin pigment formation. Further, we performed allele‐specific CRISPR/Cas9‐targeted knockouts of the pigment‐related transcription factor, apontic‐like ( apt‐like ) in B. mori × B. mandarina F1 hybrid individuals which exhibit B. mandarina ‐like larval pigmentation. Knockout of the B. mandarina allele of apt‐like in F1 embryos results in white patches on the dorsal integument of larvae, whereas corresponding knockouts of the B. mori allele consistently exhibit normal F1 larval pigmentation. These results demonstrate a contribution of apt‐like to the evolution of reduced melanin pigmentation in B. mori . Together, our results demonstrate the feasibility of CRISPR/Cas9‐targeted knockouts as a tool for understanding the genetic basis of traits associated with B. mori domestication . Abstract : Bombyx mori and its wild progenitor are an important model for the study of phenotypic evolution associated with domestication. As proof‐of‐principle, we used CRISPR/Cas9 to generate knockouts of two melanin pigmentation‐related genes. By generating a homozygous knockout of yellow‐y in B. mandarina, we confirmed this gene's role in melanin pigment formation. Further, by generating allele‐specific knockouts of apontic‐like in B. mori × B. mandarina F1 hybrids, we establish that evolution of apt‐like contributed to reduced melanin pigmentation during domestication.