Given the high performance of the Prediction strategy in simulations, we explored an experimental implementation in which Drosophila protein interactions were predicted using the cross-species method of Sharan et al.39 (Fig. 4a ). According to this method, existing protein interaction networks in yeast, worm, and fly are aligned based on sequence similarity to identify conserved interaction clusters, and these alignments are used to transfer interactions that have been observed in some species but not yet in others (Fig. 4b) . A total of 1,294 interactions were predicted using this method, each of which was prioritized as a candidate with high prior probability (92.4%) based on the FDR reported by Sharan et al.39 (7.6%).