Functions of melanin synthesis genes, yellow and tan, in wing pigmentation revealed by CRISPR/Cas9-mediated mutagenesis in Drosophila guttifera.

Abstract

Colour pattern formation is a key model for studying evolutionary and developmental mechanisms. In the fruit fly Drosophila guttifera, which exhibits distinctive polka-dot wing pigmentation, we investigated the roles of two putative melanin synthesis genes, yellow and tan, using CRISPR/Cas9-mediated genome editing. We established multiple mutant strains with lesions in either gene and found that both genes were essential for normal pigmentation intensity in wing spots, though the patterns themselves persisted. Double mutants showed further reduction in pigmentation, indicating additive effects but not complete loss of patterning. Ectopic expression of wingless failed to induce normal pigmentation in yellow or tan mutants, demonstrating that both genes act downstream of wingless and are required for its pigmentation-inducing function. Furthermore, mosaic phenotypes in G0 individuals revealed quasi-cell-autonomous functions of tan, suggesting that pigmentation in D. guttifera wings depends on local availability of precursors rather than solely on transport via wing veins. This study establishes D. guttifera as a genetically tractable system for functional analyses and contributes to understanding the molecular basis of insect colour pattern formation.