Direct Parental (DIPA) CRISPR in the jewel wasp, Nasonia vitripennis

While clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technology has demonstrated remarkable promise as a gene-editing tool, its application in certain insects, such as the jewel wasp, Nasonia vitripennis, has been hindered by a lack of a tractable method for reagent delivery. Direct Parental (DIPA-) CRISPR recently emerged as a facile way to induce gene lesions because it involves adult injection with commercially available Cas9-sgRNA with no helper reagent. However, DIPA-CRISPR has so far been tested in only a few insects. Here, we have assessed the amenability of DIPA-CRISPR in N. vitripennis by targeting two eye pigmentation genes, cinnabar and vermilion, which function in the ommochrome pathway. Successful generation of lesions in both genes demonstrated the functionality of DIPA-CRISPR in N. vitripennis and its potential application to other genes, thereby expanding the range of insects suitable for this method. We varied two parameters, Cas9-sgRNA concentration and injection volume, to determine optimal injection conditions. We found that the larger injection volume coupled with either higher or lower reagent concentration was needed for consistent mutation production. However, DIPA-CRISPR yields an overall low mutation rate in N. vitripennis when compared to other tested insects, a characteristic that may be attributed to a proportionally low vitellogenic import efficiency in the jewel wasp. We discuss different factors that may be considered in determining when DIPA-CRISPR may be preferable over other reagent delivery methods.