Multiplexed GuideRNA-expression to Efficiently Mutagenize Multiple Loci in Arabidopsis by CRISPR-Cas9.

Since the discovery of the CRISPR (clustered regularly interspaced short palindromic repeats)-associated protein (Cas) as an efficient tool for genome editing in plants (Li et al., 2013; Shan et al., 2013; Nekrasov et al., 2013), a large variety of applications, such as gene knock-out, knock-in or transcriptional regulation, has been published. So far, the generation of multiple mutants in plants involved tedious crossing or mutagenesis followed by time-consuming screening of huge populations and the use of the Cas9-system appeared a promising method to overcome these issues. We designed a binary vector that combines both the coding sequence of the codon optimized Streptococcus pyogenes Cas9 nuclease under the control of the Arabidopsis thaliana UBIQUITIN10 (UBQ10)-promoter and guide RNA (gRNA) expression cassettes driven by the A. thaliana U6-promoter for efficient multiplex editing in Arabidopsis (Yan et al., 2016). Here, we describe a step-by-step protocol to cost-efficiently generate the binary vector containing multiple gRNAs and the Cas9 nuclease based on classic cloning procedure.