Powerful, efficient QTL mapping in Drosophila melanogaster using bulked phenotyping and pooled sequencing

Area of Science:

• Genetics
• Genomics
• Quantitative Trait Locus (QTL) Mapping

Background:

• Recombinant inbred lines (RILs) are valuable for dissecting complex traits but are challenging to manage.
• Bulked segregant analysis (BSA) using extreme phenotypes offers an alternative approach.

Purpose of the Study:

• To develop and validate an extreme quantitative trait loci (eQTL) mapping strategy.
• To leverage the Drosophila Synthetic Population Resource (DSPR) for eQTL analysis.
• To compare the power and resolution of eQTL mapping with traditional RIL-based QTL mapping.

Main Methods:

• Phenotyping and genotyping a large segregating population derived from the DSPR.
• Utilizing an extreme segregant analysis paradigm with pooled DNA sequencing.
• Simulating eQTL designs to determine optimal parameters (replicates, individuals, selection intensity).
• Empirically applying the eQTL strategy to map caffeine resistance loci in Drosophila.

Main Results:

• Simulations show eQTL mapping achieves comparable power and sub-centimorgan resolution to RIL mapping with feasible experimental designs.
• An empirical eQTL experiment identified 7 quantitative trait loci (QTLs) for caffeine resistance.
• Two identified QTLs validated previously discovered loci, and 6/7 were associated with strong candidate genes.
• RNAi knock-downs confirmed the involvement of 4 genes in caffeine resistance.

Conclusions:

• The described extreme quantitative trait loci (eQTL) mapping strategy is a powerful and advantageous alternative to traditional methods for complex trait dissection.
• This approach, combining bulked phenotyping and genotyping, is particularly suitable for traits of interest in Drosophila research.
• The study provides empirical validation for the eQTL method's effectiveness and efficiency.