We tested the influence of w and mini-w on ethanol sedation in two behavioral assays, one based on bang-induced climbing (eRING) and another based on ethanol sedation. Knock-down of mini-w and a null mutation in the endogenous w locus increased sensitivity to ethanol sedation in eRING assays, whereas the same genetic manipulations of mini-w and w had no major effect on ethanol sensitivity measured in sedation assays. Therefore, the eRING assay should not be used for measuring ethanol sensitivity in studies with transposons marked with mini-w or studies that otherwise compare genotypes with unequal expression of w or mini-w. Considering the wide-spread use of transposons marked with mini-w and that expression of mini-w can vary considerably between independent transposon insertion strains (Hazelrigg et al., 1984; Silicheva et al., 2010), this is a significant limitation to the utility of the eRING assay for genetic studies on ethanol sensitivity in Drosophila. In contrast, the ethanol sedation assay described here can be used as an experimental platform for probing the genetic basis for ethanol sensitivity and tolerance using many existing fly strains including those with mini-w transgenes.
