Design of Multiplexing CRISPR/Cas9 Constructs for Plant Genome Engineering Using the GoldenBraid DNA Assembly Standard.

Due to the huge potential of CRISPR/Cas9 for synthetic biology and genome engineering, many plant researchers are adopting this technology in their laboratories. CRISPR/Cas9 allows multiplexing of guide RNAs (gRNAs), therefore targeting several loci in the genome simultaneously. However, making DNA constructs for this purpose is not always straightforward for first-time users. Here we show how to make multiplex CRISPR/Cas9 constructs using the GoldenBraid (GB) DNA assembly system. As an example, we create a polycistronic gRNA construct that guides a dead version of Cas9 to three different positions of the nopaline synthase promoter, leading to transcriptional repression. After a description of the reagents, the protocol describes step-by-step the considerations for DNA target selection and the molecular cloning process of the final T-DNA construct as well as its testing by transient expression in Nicotiana benthamiana leaves along with a reporter construct for luciferase expression.