The type II CRISPR/Cas system from Streptococcus pyogenes and its simplified 
derivative, the Cas9/single guide RNA (sgRNA) system, have emerged as potent new 
tools for targeted gene knockout in bacteria, yeast, fruit fly, zebrafish and 
human cells. Here, we describe adaptations of these systems leading to 
successful expression of the Cas9/sgRNA system in two dicot plant species, 
Arabidopsis and tobacco, and two monocot crop species, rice and sorghum. 
Agrobacterium tumefaciens was used for delivery of genes encoding Cas9, sgRNA 
and a non-fuctional, mutant green fluorescence protein (GFP) to Arabidopsis and 
tobacco. The mutant GFP gene contained target sites in its 5' coding regions 
that were successfully cleaved by a CAS9/sgRNA complex that, along with 
error-prone DNA repair, resulted in creation of functional GFP genes. DNA 
sequencing confirmed Cas9/sgRNA-mediated mutagenesis at the target site. Rice 
protoplast cells transformed with Cas9/sgRNA constructs targeting the promoter 
region of the bacterial blight susceptibility genes, OsSWEET14 and OsSWEET11, 
were confirmed by DNA sequencing to contain mutated DNA sequences at the target 
sites. Successful demonstration of the Cas9/sgRNA system in model plant and crop 
species bodes well for its near-term use as a facile and powerful means of plant 
genetic engineering for scientific and agricultural applications.