The type II CRISPR/Cas9 system (clustered regularly interspaced short 
palindromic repeats/CRISPR-associated) has recently emerged as an efficient and 
simple tool for site-specific engineering of eukaryotic genomes. To improve its 
applications in Drosophila genome engineering, we simplified the standard 
two-component CRISPR/Cas9 system by generating a stable transgenic fly line 
expressing the Cas9 endonuclease in the germline (Vasa-Cas9 line). By injecting 
vectors expressing engineered target-specific guide RNAs into Vasa-Cas9 fly 
embryos, mutations were generated from site-specific DNA cleavages and 
efficiently transmitted into progenies. Because Cas9 endonuclease is the 
universal component of the type II CRISPR/Cas9 system, site-specific genomic 
engineering based on this improved platform can be achieved with lower 
complexity and toxicity, greater consistency, and excellent versatility.