Still little is understood about the nucleotide changes that underlie variation in complex phenotypes. Variation in the PPARgamma-homolog Eip75B has previously been suggested to be associated with longevity and life-history differences in the fruit fly Drosophila melanogaster. Using RNAi knockdown, we first demonstrate that reduced expression of Eip75B in adults affects lifespan, egg laying rate and egg volume. To then test the effect of a naturally occurring SNP variant within a cis-regulatory domain of Eip75B, we screened wildtype lines with alternative alleles and conducted precise genome editing using CRISPR/Cas9. These experiments revealed that this natural polymorphism has a significant effect on fecundity and egg-to-adult viability, but not on longevity or other life-history traits. These results provide a rare functional validation for the role of a natural allelic variant in adaptation of life-history traits directly linked to fitness at the single nucleotide level.
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