Genome editing of model organisms is essential for gene function analysis and is thus critical for human health and agricultural production. The current technolo- gies used for genome editing include ZFN （zinc-finger nuclease）, meganucleases, TALEN （Transcription activa- tor-like effector nucleases）, etc. . These technologies can generate double stranded breaks （DSBs） to either disrupt gene function through generation of premature stop codons by non-homologous end joining （NHEJ） pathway, or to facilitate gene targeting through homolo- gous recombination （HR） with an incoming template. Recently, a new technology for genome editing, CRISPR （Clustered Regularly Interspaced Short Palindromic Re- peats）/Cas （CRISPR-associated） systems, has been de- veloped . CRISPR/Cas systems are adaptive defense systems in prokaryotic organisms to fight against alien nucleic acids . The spacer sequences acquired from foreign DNA are positioned between host repeats, and transcribed together as CRISPR RNA （crRNA）. In the type II CRISPR system, a single nuclease Cas9, guided by a dual-crRNA：tracrRNA, is sufficient to cleave cog- nate DNA homologous to the spacer . Efficient cleav- age also requires the presence of protospacer adjacent motif （PAM） 5＇-NGG-3＇ following the spacer sequence. The dual-crRNA：tracrRNA has been further streamlined to a single RNA chimera, called sgRNA （single guide RNA） . Compared with protein-guided technologies, CRISPR/Cas system is much easier to implement, as only short guide RNAs need to be customized to target the genes of interest. Up to now, the CRISPR/Cas sys- tem has been successfully applied to efficient genome editing in many eukaryotic organisms including human , mice , zebra fish , fly , worm , and yeast . However, the application of CRISPR/Cas system in plants has not been reported. Rice （Oryza sativa L.） is a major staple crop in the grass family （Poaceae）, feed- ing half of the world＇s population.