More than meets the eye: mutation of the white gene in Drosophila has broad phenotypic and transcriptomic effects.

The white gene, one of the most widely used genetic markers in Drosophila research, serves as a standard background mutation for transgene insertions and genetic manipulations. While its primary function involves eye pigmentation, mutations in white have been associated with diverse phenotypic effects, including those related to metabolism, behavior, and stress responses. However, many of the published studies do not account for differences in genetic background, raising concerns about the interpretation of experimental results. To address this, we generated fly lines through 10 generations of backcrossing that are highly genetically similar except at the white locus, minimizing background variation. Given the likely metabolic consequences of white gene deletion and its role in neurotransmitter production, we focused on behavioral, metabolic, and fitness-related traits and performed transcriptomic analysis on adult fly heads. Our findings both confirm and refine previous observations, revealing that some reported effects of white mutation are robust while others likely reflect underlying genetic background differences. These results emphasize the necessity of genetic background control in Drosophila research and warrant caution when using white mutants as a baseline for comparative studies.