The discovery of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and Cas9 (CRISPR associated system or CRISPR associated protein 9 nuclease) found in bacteria to work as a defense mechanism against foreign DNA has proven to be an invaluable tool to target and modify a genetic sequence in gene editing and genome engineering applications. The system, known as CRISPR/Cas9, allows for sequence-specific cleavage of a targeted genomic locus by delivering the RNA-guided Cas9 nuclease and appropriate guide RNAs (gRNA) into a cell. In addition, Protospacer Adjacent Motif (PAM) sequence immediately following the specificity sequence is necessary for successful binding of the Cas9 nuclease. It is important and critical to monitor the level of Cas9 editing protein or track the Cas9 editing protein in transfected cells, as it will tell transfection efficiency and optimize the editing process in the total cell population. Staphylococcus aureus Cas9 (SaCas9)-mediated genome editing has been reported in human cells and Arabidopsis. Because SaCas9 (1053 a.a.) is smaller than Streptococcus pyogenes Cas9 (SpCas9) (1368 a.a.), SaCas9 could have substantial advantages for delivering and expressing Cas9 protein, especially using virus vectors.